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' v l l mu; lllylll llll lg l l u ll l l m R A R Y 18 Michigan State University TH ESYS This is to certify that the thesis entitled RESPONSES TO DISTRESS SIGNALS IN BOBWHITE QUAIL (Colinus virginianus) presented by Mary Lee Nitschke has been accepted towards fulfillment of the requirements for Ph- D- degree in mm J:¥?£:::/;?ié2%ég22:’ Major professor Date /9 €4,241? 737 0-7539 RESPONSES TO DISTRESS SIGNALS IN BOBNHITE QUAIL (Colinus virginianus) By Mary Lee Nitschke A DISSERTATION Submitted to Michigan State University in partial fulfiliment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Psychology 1978 ABSTRACT RESPONSES TO DISTRESS SIGNALS IN BOBNHITE QUAIL (Colinus virginanus) By Mary Lee Nitschke Two studies examined three main hypotheses regarding responses to Bobwhite quail in a laboratory situation to recorded distress vocalizations of conspecifics and of members of other species. The first prediction was that recorded distress calls would elicit defen- ssive responses and suppress nondefensive responses in Bobwhite quail. Second, conspecific distress calls were expected to be the most effec- tive, especially in eliciting the defensive response of freezing. For distress calls of other species, the closer the evolutionary relationship between the species, the more effective the distress calls should be in eliciting freezing. Finally, because results of earlier studies of habituation (or decrement of response) to repeti- tions of distress vocalizations have been equivocal, the prediction regarding habituation was made in the form of the null hypothesis, that no habituation would be observed in any signal condition. Because Bobwhite quail are highly social animals, triads of birds (two males, one female) housed together were also tested together. The general procedure was the same in both studies. A triad of bi rds Mary Lee Nitschke first underwent habituation to the experimental chamber, a sound- proofed box equipped with speakers for auditory stimulus presentation and that permitted behavioral observation. All triads were then observed for a six-minute behavioral baseline period. Following the baseline, all triads first heard one trial of a recording of Bobwhite quail food call, after which three trials of the auditory stimulus appropriate for the triad's experimental group were presented. A trial consisted of two five-second presentations of a call with a ten second intersignal interval. Intertrial intervals were at least two minutes. In Study l, independent groups of six triads of birds each heard either Bobwhite quail distress call or taped silence following the food call. In Study 2, independent groups of five triads of birds each heard one of six auditory signals following the food call: Bobwhite quail distress call, chicken distress call, blue jay distress call, rabbit distress call, reversed Bobwhite quail distress call con- trol, and Bobwhite quail food call control. Because Bobwhite quail in groups tend to act in concert, average frequencies of response for each triad of birds constituted the basic unit of analysis. Spectro- graphic analyses of the stimulus calls were also prepared. Results of both studies generally supported the first hypothe- sis. All distress calls did elicit defensive responses, and some non- defensive responses (such as vocalization) were suppressed although others (such as preening) were not. Hypothesis Two was partially supported. Among avian species, Bobwhite quail distress calls were Mary Lee Nitschke most effective in altering responding, with chicken distress calls next most effective and blue jay distress calls lease effective--a decrease in order of degree of evolutionary relatedness, as predicted. However, rabbit distress calls were as effective as conspecific dis- tress calls in affecting the behavior of Bobwhite quail. This result may reflect different temporal attributes of the rabbit distress call as revealed by spectrographic analyses of all of the calls. A very different explanation may be that the rabbit, though further removed phylogenetically from Bobwhite quail than other avian species, none- the less shares the same ecological niche as Bobwhite quail, and so rabbit distress calls have strong signal value for these animals. Finally, responses to these auditory signals clearly showed habitua- tion over trials in this laboratory setting. A primary question motivating this research was whether dis- tress calls communicate universally: Is a scream a scream in any language? The results of these studies show that the responses elicited by a "scream" are constrained by several contingencies, including phylogenetic relationships, environmental contingencies, and what the animal is doing when it first hears the scream. DEDICATION To "Ell who loved who cared who helped who believed in memory of CorriAnne and Rusty and Stan whose interactions brought it all together for me. ii ACKNOWLEDGMENTS I appreciate the guidance and support of my committee members throughout this study and throughout my graduate career at Michigan State University. Support staff members also contributed to this endeavor, especially Marv, Gary and Jack in the shop. Several con- sultants provided assistance: Johnny Steward, J. L. Gulledge, and Oscar Tosi. The time and effort and intimate involvement of a number of students in this study was greatly appreciated: special mention is due to Chris, Dale, Jackie, Laurie, Mary, Rick, Terry, and Woody. Special thanks are due to my most essential support group: Ellen, Barb, Larry, and all my friends at MEALSN. TABLE OF CONTENTS Page LIST OF TABLES . . . . . . . . . . . . . . . vi LIST OF FIGURES . . . . . . . . . . . . . . . viii LIST OF APPENDICES . . . . . . . . . . . . . . x INTRODUCTION . . . . . . . . . . . . . . . . l The Present Study. l Distress Calls . . . . . . . . . . 3 Description of Distress Calls . . . 3 Responses Elicited by Conspecific Distress Signals . 6 Approach Toward Distress Signals 7 Avoidance of Distress Signals . . . . . . . . 8 Interspecific Communication of Distress . . . 10 Experimental Studies of Interspecific Communication of Distress . . . . . . . . . . . . . 13 Freezing. . . . . . . . . . . . . . l7 Habituation Studies . . . . . . . . . . l9 Bobwhite Quail as a Preparation . . . . . . . . 24 Pilot Nork . . . . . . . . . . 27 Aims and Purposes of This Study . . . . . . . . 29 METHOD . . . . . . . . . . . . . . . . . . 3l Subjects . . . . . . . . . . . . . . . . 3l Apparatus . . . . . . . . . . . . . . 35 Testing Chamber . . . . . . . . . . . . . 35 Stimulus Materials . . . . . . . . . . 36 Bobwhite Quail Vocalizations . . . . . . . . 40 Vocalization from Other Species . . . . . . . 4i Stimulus Delivery Apparatus . . . . . . . . . 43 Data Collection Apparatus . . . . . . . . . 44 Habituation to the Apparatus . . . . . . . . 45 Procedure . . . . . . . . . . 46 Basic Testing Procedure . . . . . . . . . . 46 Response Measures . . . . . . . . . . . . . 49 Activities . . . . . . . . . . . . . . 49 iv Postural Patterns . . . . . . . . . . . . 50 Scoring . . . . . . . . . . . . . . . 53 Reliability . . . . . . . . . . . . . . 55 Data Analysis . . . . . . . . . . . . . 56 RESULTS . . . . . . . . . . . . . . . . . . 60 Studies 1 and 2 . . . . . . . . . . . . . 60 Study 1 . . . . . . . . . . . . . . . 64 Study 2 . . . . . . . . . . . . 73 Study 2 Habituation . . . . 93 Study 2 Food Call vs. Trail l of Test Signal . . . lOS DISCUSSION . . . . . . . . . . . . . . . . . ll8 Stimulus Properties of Distress Calls . . . . . . llB Summary of Expected findings . . . . . . . . . llB Unexpected Results . . 123 Implications for Theory or Research and Generaliza-O bility. . . . . . . . . . . . . . . . 127 APPENDICES . . . . . . . . . . . . . . . . . 129 REFERENCES . . . . . . . . . . . . . . . . . 166 Table LIST OF TABLES Experimental Design Summary: Study l and II . Percent Agreement Across Nine Behavior Categories that a Behavior Did or Did Not Occur for Five Pairings of Four Individuals who Participated as Observers in Study 2 A Summary of Measurements Taken from Spectrographic Analysis of Stimulus Signals . . . . . Analysis of Variance of Freezing Responses in Two Inde- pendent Groups of Bobwhite Quail, One exposed to Taped Silence and the Other Exposed to Bobwhite Quail Dis- tress Calls, Tested During a Baseline Period and During .Signal Presentation Periods in Study l . Summary of Results of Analyses of Variance for Fre- quencies of 15 Different Behavior Categories Exhibited by Two Independent Groups of Bobwhite Quail, One Exposed to Taped Silence and the Other Exposed to Bobwhite Quail Distress Calls, Which Were Tested During a Baseline Period and During Signal Presenta- tion Periods in Study 1 . . . . . . . Analysis of Variance of the Freezing Response in Bobwhite Quail During Baseline and Signal Test Periods with Independent Groups Assigned to One of Six Signal Conditions: Bobwhite Quail Distress Call, Bluejay Distress Call, Rabbit Distress Call, Chicken Distress Call, Reversed Bobwhite Quail Distress CalL and Bob- white Quail Food Call . . . . Summary of Significance Levels of Results of Analyses of Variance on Frequencies of ll Behavior Categories Measured in Study 2, Across Six Independent Signal Conditions and from Baseline to Signal Presentation Periods within Each Signal Condition . vi Page 32 57 62 66 69 75 79 Table 10. 11. 3-1. 8-2. E-Z. Analysis of Variance of Incidence of Habituation of Freezing Responses Over Three Signal Repetitions for Six Independnet Groups of Bobwhite Quail Assigned to One of the Following Stimulus Conditions: Bobwhite Quail Distress Call, Chicken Distress Call, Blue Jay Distress Call, Rabbit Distress Call, Reversed Bobwhite Quail Distress Call, and Food Signal Control Call Analysis of Variance Results Summarized for Those Behavior Categoreis that were Statistically Signifi- cant in Study 2 . . . . . . . Analysis of Variance of the Freezing Response in the Bobwhite Quail Under Six Signal Conditions Testing Responding to the Common Bobwhite Food Call versus Responding to Trail One of the Experimental Stimulus Signal . . . . . . . . . Summaries of Analyses of Variance of Frequencies of Occurrence for Eight Behavior Categories in Response to an Initial Auditory Food Call Stimuls and the First Trail of Experimental Auditory Stimulus for Independent Groups of Bobwhite Quail each Exposed to One of Six Auditory Distress Signal Stimuli Study 1. Table of Means and Standard Deviations for Taped Silence and Bobwhite Distress Signal Conditions During Baseline and Signal Period Tests Analysis of Variance for Study 1 . Table of Means and Standard Deviations for Six Signal Conditions During Baseline and Signal Period Tests-- Study II . . . Analysis of Variance for Study 11: Basic Analysis . Table of Means and Standard Deviations for Six Signal Conditions Over Three Stimulus Trials Analysis of Variance for Study II: Habituation . Table of Means and Standard Deviations Comparing Responding During the Common Food Call Versus Responding on Trial One Over Six Signal Conditions in Study 11 . . . . . . . . . Analysis of Variation for Study II: Food Call versus Trial 1 . . . . . . . vii Page 95 101 107 112 140 141 147 148 153 154 158 159 LIST OF FIGURES Figure Page l. Temporal sequence of signals on all signal stimulus tapes . . . . . . . . . . . . . . . . 37 2. Mean responses in five behavior categories made by two independent groups of Bobwhite quail, one group exposed to Bobwhite quail distress signals and one exposed to taped silence and both tested during pre- signal baseline and post-signal phase presentation periods . . . . . . . . . . . . . . . . 67 3. Mean responses in five categories of nondefensive behaviors made by two independnt groups of Bobwhite quail, one group exposed to Bobwhite quail distress calls and one group exposed to taped silence, with both tested during pre-signed baseline and post- signal presentation periods or phases . . . . . . 7l 4. Mean freezing responses of Bobwhite quail during pre- signal baseline and post-signal presentation periods for six groups of birds each of which heard a differ- ent auditory stimulus . . . . . . . . . . . 76 5. Mean pecking responses of Bobwhite quail during pre- signal baseline and post-signal periods to each of six auditory signal conditions . . . . . . . . 80 6. Mean dusing reSponses of Bobwhite quail during pre~ signal baseline and post-signal periods to each of six auditory conditions . . . . . . . . . 83 7. Mean proximity responses of Bobwhite quail during pre-signal baseline and post-signal periods to each of six auditory signal conditions . . . . . . . 86 8. Mean locomotion reSponses of Bobwhite quail during pre-signal baseline and post-signal periods to each of six auditory signal conditions . . . . . . . 88 9. Mean vocalization responses of Bobwhite quail during pre-sigal baseline and post-signal periods to each of six auditory signal conditions . . . . . . . 9l viii Figure 10. 11. 12. 13. 14. Habituation analysis: Mean defensive freezing responses per interval over three repeated experimental auditory signals showing significant habituation . . . . . . . . . . Habituation analysis: Mean pecking and dusting responses of Bobwhite quail over three repetitions of auditory signals . . . . . . . . . . Habituation analysis: Mean cautious posture responses and vocalization responses of Bobwhite quail over three repeated auditory signals . Mean defensive freezing responses of a food call signal and to the first experimental signal, Trial 1 . Mean proximity responses to food call and to first experimental signal . . . . ix Page 96 99 103 108 113 Appendix A. B. LIST OF APPENDICES Samples of Raw Data Scoring Sheets Data Analysis for Study I Taped Silence vs. Bobwhite Distress Signal . . . . Data Analyses for Study II Six Signal Conditions-- Baseline vs. Signal Test Period . . Data Analysis for Study II Six Signal Conditions-- Habituation . . . . Data Analysis Study II Six Signal Conditions: Food Call vs. Trial 1 . . . Spectrogram Samples of Signal Stimuli Page 130 139 146 152 157 162 INTRODUCTION The Present Study Behaviors that are typically called communicating range over all the classes of consummatory behavior (Denny & Ratner, 1970). In birds, these behaviors generally involve postural displays and vocali- zations. Of particular interest here is the issue of how birds respond to the category of communications known as distress signals when heard in a laboratory situation. Three main questions are asked. The first question concerns how bobwhite quail respond upon hearing the distress vocalization of a member of its own species (conspecific vocalization). Within the constraints of the laboratory, the present study takes a look at the question, "What does the animal do when presented with a recorded distress call of a bobwhite quail as an isolated auditory stimulus?" Some theorists (e.g., Lieberman, 1977) have suggested that one of the universals in communication among different species (inter- specific communication) is the distress signal. Put in a more general way, one might ask whether a scream is a scream in any language. Background information obtained from animal breeders, and also from human mothers, support the notion that humans readily respond to the distress vocalization of other species of animals. The second ques- tion of interest for the present study, then, is to observe how the bobwhite quail responded to the distress vocalizations of species at different degrees of evolutionary relatedness to themselves. Habituation, the waning of a response with repeated stimu- lation, is one of the most basic learning phenomena. The circum— stances under which habituation of defensive, survival, and fear responses might occur is an unresolved issue (Hinde, 1970). Habitua- tion of fear responses to visual stimuli and to some auditory stimuli is readily observed in the laboratory and in situations in which artificial predators are used (Leibrecht, 1974). However, in situa- tions using auditory stimuli (Zeiner & Peeke, 1970) and in those using live predators as stimuli (Curio, 1975), habituation is not consistently observed. In the present study, then, the third ques- tion of interest was whether habituation would be observed to auditory distress stimuli over three repetitions of the stimuli in a laboratory situation. Birds have natural defensive responses to alerting signals. The defensive distance model proposed by Ratner (1967) suggests that when an animal's survival is threatened from a very short distance, one of the highly probable responses will be freezing, or immediate cessation of all movement. The present study examines both defensive responses such as freezing and nondefensive responses such as pecking and preening made in reSponse to auditory distress signals and to nondistress comparison signals. To clarify and elaborate on the rationale for considering these questions, the remainder of this introductory chapter covers the following topics: (1) Distress signals, the responses which they elicit, and the available data regarding interspecific communication of distress; (2) Freezing as a defensive response; (3) Habituation and its implications in the case of defensive responses; and (4) The attributes of bobwhite quail which make them a good choice as experi- mental animals for this study. Finally, some pilot work is described which served as a basis for a number of procedural decisions made for this study. Distress Calls Description of Distress Calls A distress call refers to the call or vocalization given by a captive bird (or other animal) when seized by a predator or held by a human. Distress calls are different from alarm calls, which are the calls given by a bird (or other animal) that is itself free when it sights some potential danger. This distinction, made by Frings and Frings (1968) and accepted by most investigators, is used throughout this paper. A distress call typically has the characteristic of being a loud, repetitive burst of sound that includes a wide range of fre- quencies, with the fundamental frequencies generally slurred and downward sloping when examined spectrographically. Kok (1971) notes that the distress call has a piercing, harsh, squealing quality in the grackle, and many writers mention this aspect of this call in a variety of species. Johnsgard (1975) says that the typical quail distress call is loud and piercing, with a broad frequency range, and has other characteristics such as sudden onset and repetitiveness that made the signal easy to localize (Erulkar, 1972). Cink (1971) has studied spectograms for several species of quail and notes that the distress call is nearly identical even among rather distantly related quails. These descriptions agree with the signal character- istics specified by Marler (1957) as the ideal sound needed for a bird to localize its source: A high pitch for location by intensity difference, a low pitch for location by phase difference, and a sharply broken and repetitive sound for location by time difference. The distress calls of adults in several of the galliformes look quite similar spectrographically. Collias and Joos (1953) discuss such attributes in the distress signal of the domestic fowl, and Williams (1969) shows that for the Califbrnia quail, although there is some variation between individuals, the configuration of the call is the same regardless of sex of bird or individual bird making the call. Williams also shows that the call is very similar for both the California quail and the bobwhite quail. Ellis and Stokes (1966) note that the distress call of the chukar partridge, the gambel quail, the California quail and the domestic fowl are pictorially analogous. Since the universality of effect of distress calls is one issue of concern for this research, it is interesting that the dis- tress call of other animals and some mammals share some of the char- acteristics discussed above. Smith, Smith, Oppenheimer and Devilla (1977) note that the scream of the black-tailed prairie dog is elicited when this wild dog is caught in a leg trap or when it is handled by.a human (a standard procedure for eliciting distress calls in many species). Waring (1970) shows the typical signal character- istics for prairie dogs, which is a clear, high-pitched, variable (or complex) signal with a sudden onset. Smith et a1. (1977) state that the prairie dog scream appears to encode a message of "escape if feasible," but this team did not specifically test responsiveness of the prairie dogs to this signal. Brand (1976) mentions that chip- munks, when attacked, emit a squeal, a high-pitched (up to l4KHz) complex sound. This is especially true if they are bitten. His spectrogram for the chipmunk appears similar to other recordings of distress signals. Scott (1968) and Compton and Scott (1971) have shown that the distress cry of a domestic canine puppy is characterized by a number of different kinds of sounds, highly variable in form and pitch. It is a mixture of yelps and squeals in no particular order which serve as distress signals that are easily localized. They suggest that the function of this form of the signal is to prevent habituation in the listener. For experimental purposes, the most common method of elicit- ing a distress signal from birds and small animals is to capture and hold the animal by the feet. Investigators disagree as to whether or not it is necessary to allow the wings of birds to remain free to flap, but the necessary condition appears to be holding the bird by the feet. Numerous investigators, including most mentioned herein, state that this hand-elicited distress call is the same call that is given when a bird is captured by a predator. Stefanski and Falls (1972a) have made spectrographical comparisons of a distress call from a hand-held bird with that given by a bird captured by a hawk. They found no significant differences between the two signals. Frings and Frings (1958) report a similar finding. Accordingly, the feet-holding method was used to elicit the bobwhite quail distress calls in this study. Responses Elicited by Conspecific Distress Signals Eibl—Eibsfeldt (1970) suggests that the death cry or the distress cry of many animals may function as warning signals to con- specifics. Several of the investigators mentioned above suggest that since distress calls are easily localized, they could serve to provide information to conspecifics about the location of a predator. Tinbergen (1968) further implies that distress signals may have some universality across species in that they function to turn off attack in the primate species. Similarly, Frings and Frings (1964) suggest that a human may escape attack from a great ape by screaming (scream- ing is considered to be the primate distress signal). They suggest that screaming will turn the attack behavior into a rescue or solicitation behavior pattern. They fail to mention what the conse- quences of being rescued by a great ape might be for the human. Responses to distress signals of conspecifics vary with the conditions present. Generally, a distress signal from a young animal elicits parental approach. There is an excellent review of this aspect of distress signaling by Noirot (1972) which focuses on maternal behavior. However, we are primarily concerned with this question in adult members of a species, and so such signalling by immatures or young members of a Species will not be discussed further. Frings and Frings (1964) suggest that responses to distress signals vary with the social organization of the species. Solitary species show little or no reaction to distress signals, whereas species that are moderately dispersed are attracted by the distress signal of a conspecific, which often elicits mobbing. In compact flock birds, e.g., starlings, the distress signal is a strong repellent and will disperse an entire flock, danger to one member implies danger to the others. Approach Toward Distress Signals Let us first examine some instances in which the response to a conspecific distress signal is a positive phonotaxis, that is, approaching the source of the sound. (It must be remembered that it is not clear in all of these cases that it is only the auditory component of the signal that may be the effective stimulus.) Fret- well (1973) notes that a bluebird caught in a mist net screams when handled, and that this elicits mobbing by conspecifics. Generally other passerines are also attracted to a bird emitting distress signals in the net. Stefanski and Falls (1972a), using a playback paradigm, found that conspecifics (sparrows) approached the speaker and produced alarm calls and threat displays. A further observation, reported by Falls in the above-mentioned report, describes a blue jay being attacked by a sharp-shinned hawk. The screaming jay elicited approach by_the other jays with the result that the hawk released the screaming jay and flew off. Kok (1971), investigating the grackle, and Chamberlain and Cornwell (1971) playing crow distress cries, both report that conspecifics were attracted to the source of the sound, approached, and showed alarm behaviors. Eibl-Eibesfeldt (1970) reports that many apes and monkeys will attack blindly if a conspecific gives a distress call upon being handled by the keeper or caretaker, even though their keeper is a familiar stimulus. Forsythe (1970) reporting on the behavior of a passerine, the long billed curlew, observes that this species' response to hearing a conspecific distress signal is to crouch and freeze. In quail, a social species, both Stokes (1967) and Johns- gard (1975) report that distress calls from other quail attract conspecifics and may result in attempted assistance and the elicita- tion of alarm calling. Stokes mentions several instances of being attacked by males if he elicited a distress cry from a bird he cap- tured from the same pen occupied by the attackers. Avoidance of Distress Signals Conspecific distress signals can also produce negative phonotaxis, or fleeing from the source of the sound, a phenomenon which fruit growers and others have found useful for its practical applications in controlling birds' behavior. Frings and Frings (1968) give an excellent review of the practical uses of bioacoustic methods to control problem species of birds and insects. Frings and Jumbar (1954) report that a starling distress call played at night in a starling roost will clear large areas of starlings if played consecutively for several nights. Frings, Frings, Jumbar, Busnel, Bigan, and Gramet (1958) report the results of several stud- ies involving crows. The distress call of crows living in France (C. monedula) played to mixed flocks of birds feeding in the fields served to disperse the flocks in about 75% of the cases tested. They also ran tests (played distress calls) at night in roosts of mixed members of the Corvid family. The birds would disperse and stay away from 3 to 30 days before returning. When the distress signal of the French crow was played to crow populations in the United States, the U. 5. birds showed no response. And when crow vocalizations taped in the U. S. were played to the French crows, they were only minimally responsive. Although most writers concur with Smith's (1978) suggestion that it is not likely that there would be regional dialects in bird calls (as opposed to bird songs which do show differential dialects), the France-United States study suggests that the possibility of dialects in calls would bear investigating, at least for these species. Whether they represent approach or avoidance, the responses to conspecific distress signals can be categorized as defensive responses. On the basis of the findings reviewed, it is predicted that the presentation of conspecific distress calls to bobwhite quail will result in the elicitation of defensive responses and in the suppression of nondefensive responses. 10 Interspecific Communication of Distress Alcock (1975) argues that, as a result of convergent evolu- tion, interspecific communication of danger readily occurs. For example, totally unrelated species might exhibit behavior patterns that are remarkably alike because such patterns are effective. Their effectiveness reflects the evolution of similar responses because of similar selection pressures, i.e., convergent evolution. Hinde (1970), commenting on the adaptiveness of behavior, also notes that signal movements have been subject to selection for their efficiency. In fact, Marler (1957) has found that signals are transmitted by simple sounds which may be shared by several species. The alarm calls given by passerines when a hawk flies over are almost identi- cal for the reed bunting, the blackbird, the great titmouse, the blue titmouse and the chaffinch. Similarly, mobbing calls of birds from several families show convergence (Marler, 1959). The form of calls varies with their function. This is illustrated by the alarm calls for all of the species mentioned above, which sound like a high thin whistle. These calls share the characteristics of long duration, no sudden changes in pitch, and of beginning and ending gradually, all of which are elements which do not convey information about the position of the calling bird. There is considerable support in the literature for inter- specific similarity of alarm and warning calls among birds that share a habitat. Since we will not be dealing specifically with alarm calls in this dissertation, the reader is referred to Hinde's 11 Bird Vocalizations (1969) which covers the alarm signals in detail. Frings and Frings (1964) state that almost all birds have distress signals, generally raucous shrieks, which they emit upon being captured, and that the distress calls of the higher verte- brates sound much alike. Stefanski and Falls (1972b) agree that a casual survey of the distress calls of many genera suggests that congeneric species frequently have similar distress calls. Marler (1957) in discussing the specific distinctiveness of communication signals in birds, suggests that all danger signals should be in the same category as alarm calls in which interspecific communication is common in birds, mammals, and orthopteran insects. Hinde (1970) suggests that convergence occurs in many displays associated with predators because the prey species living in a given area are better protected if they respond to each others' alerting and danger signals. It would appear then that the distress signal should have inter-specific communication value. Boudreau (1968) reports that even crude imitations of rabbit distress sounds will lure hawks, owls, and mammalian predators within rifle range, and that other birds will approach to investigate. Indeed, the whole idea of "predator calling" as a hunting technique is built on the fact that predators do respond to distress signals of various other species, the rabbit having one of the most general ones. In fact, there are at least two business firms that specialize in producing distress signals of a variety of species, to be used in 12 the field to attract animals to the source of the sound. Hand “kissing," which produces a squeaking sound, is a common field tech- nique employed by naturalists and ornithologists to lure burds within visible range. Andre, reported in Hartley (1950), states that the plumage hunters in Trinidad imitate the hooting of an owl to attract hummingbirds and other species, since this sound elicits mobbing behavior. Reports of this type are common in the general bird literature. The possibility must be kept in mind, however, that any novel sound may elicit approach and exploratory behavior in many of these species. Burtt (1967) reports an observation common to many natural- ists that the blue jay is the sentry of the woods. That is, when a blue jay screams, most of the members of the habitat hide or freeze in reSponse. To my knowledge there are no experimental investigations or verifications of this event. Another aspect of inter-specific communication that should be mentioned here is that it may not be the vocalization per s2 that is the stimulus for alerting behavior to danger signals. Riney (1951) gives a charming account of the relationship between birds and deer in a forest habitat. He notes that deer react to two main types of environmental disturbance involving birds: (1) bird sounds which indicate a sudden change in the birds' activities, such as the sudden whirr of wings and the scolding of jays, etc.; and (2) the "zones of silence" that often surround intruders as they penetrate previously undisturbed areas. He suggests the silence results from alarmed birds fleeing into the 13 canopy or freezing. The best evidence Riney offers for these obser- vations is that he has been able to induce deer to resume their normal behavior or "break their freeze" by imitating "conversational" bird calls. Experimental Studies of Inter- specific Communication of Distress Chamberlain and Cornwell (1971) played the distress calls of three sympatirc species to the common crow species in a field study. When the blue jay distress call was played, crows gathered to the speaker in five out of ten tests. For the calls of the common grackle and the starling, they reported, respectively, no response in five of six tests and on "unpredictable" response. The most thorough study of interspecific communication involv- ing distress signals has been done by Stefanski and Falls (1972a & 1972b), studying members of the Fringillidae (the song sparrow, the swamp sparrow, and the white—throated sparrow). Using distress calls recorded from birds captured in mist nets or captured and held by the feet, they investigated both intra- and inter-specific responses in these species. The calls were played to territorial pairs in successive stages of the breeding cycle. Responses measured were approach, movement about the speaker, alarm calls, and dis- plays, latency of response, closeness of approach, number of move- ments, and number of calls elicited. Both males and females showed peak periods of responsiveness in all categories in the nest- building, egg laying, late nestling, and fledgling stages of the 14 breeding cycle. In the inter-specific study, the song and swamp sparrows responded strongly to each other's calls, which are alike in length, carrier frequency, and frequency range and which overlap broadly in the rate of frequency modulation. The white-throated sparrow, whose calls differ in these properties, responded only weakly to the distress calls of the other species. As might be expected, the white-throated distress signal elicited only weak reSponses from the song and swamp sparrows. Stetanski and Falls also found considerable variability in different dependent variables; intra-specific responding was stronger in the calling rate and move- ments measures but not in the closeness of approach or latency to respond. Two other manipulations in this study are of specific inter- est. One of these manipulations consisted of playing artificial calls that simulated the natural distress calls in length, carrier frequency, and frequency range to song and swamp sparrows. There were no significant differences found in any of the response measures between the natural calls and the artificial calls. Song sparrows were then tested on mechanically produced calls which varied in carrier frequency, rate of frequency modulation, and length of the call. With respect to each property, the birds responded strongly if the value of that property fell within the range found in the natural calls, but they responded weakly if the value fell outside this range. Stefanski and Falls conclude that all three of these properties are used in call recognition. 15 The other interesting manipulation in this study consisted of placing a live predator in the vicinity of the speaker when playing distress calls. Briefly, there was no significant change in most of the measured dependent variables when a live predator was present. There was one major difference, however. Once the predator was in view, the responding bird directed its displays to the predator rather than to the speaker. The sparrows' displays to the predators consisted mainly of threat displays and diving attacks. The behavior of the predators used in this manipulation is also of some interest. The squirrel approached the speaker when the distress signals were presented, while the blue jay remained motion- less or froze during the distress signal until the Sparrows arrived on the scene. Stefanski and Falls suggest three functions served by inter- specific responses to distress calls: (1) the predator may be startled by the other birds' reSponding and allow the prey to escape; (2) the responding bird receives information about the preda- tor and its location; and (3) the harrassment and distraction pro- vided may enable the young to hide or escape. Distress calls may also function to teach the young about predators. Other observations suggest that the distress signal itself may have a defensive function in addition to recruiting help and spreading alarm. Stokes (1967) suggests that the onset of this sudden loud call may so alarm the predator that it momentarily releases its grip on the prey. He reports that Nygren observed a 16 Cooper's hawk catch a chukar partridge, which at once gave a loud piercing scream. In reaction, the hawk momentarily released its grip and the captured chukar escaped. Summner (1935) and Bremond (1963) report similar observations. The conspecific distress cry is a salient stimulus that may function to elicit fear or defensive responses to various species. Bolles (1970) suggests that a salient stimulus such as a distress signal elicits species-specific defense responses such as freezing and suppresses other behaviors such as grooming and exploring. Fentress (1968), studying the grooming responses of voles, found that following the presentation of a frightening stimulus such as a pain cry voles flee and/or freeze. Increasing the strength of the stimu- lus increased the duration of freezing and also the duration of suppressed grooming. Since the results of several studies indicate that distress signals can be effective interspecifically, and further suggests that degree of effectiveness of signals vary directly with phylogenetic relatedness, it is predicted that the effectiveness of distress signals of other species in eliciting defensive responses in bobwhite quail will decline in the order of increased distance between the two species along a phylogenetic scale. For signals to be used in this study, effectiveness of signal is predicted to decline from the conspecific in the order; chicken distress signal, blue jay distress signal, rabbit distress signal. 17 Freezing That freezing is a prepotent defensive response is shown by its generality across species. Robinson (1969) in classifying animal defensive systems lists freezing as the most prevalent behavioral correlate of crypsis (protecitve coloration). Hinde (1961, 1970) lists freezing as a fear response and one of the postural adaptations promoting safety from predators. Carthy (1958) suggests that cessa- tion of movement has the double advantage of making invertebrates less conspicious to enemies and less attractive to the predator. Eibl-Eibesfeldt (1961), investigating the prey killing behavior of polecats that had been fed rodents and chickens, notes that none of the experimental animals attacked either the rat or the chicken as long as the prey animal remained motionless on the spot. In both cases, once the animal started to move, the polecat pursued it. Bolles (1970), in discussing species-specific defense responses, gives a review of freezing as it pertains to the rat literature in avoidance learning. He notes that freezing is always near threshold, that it is seen whenever any novel stimulus event occurs, and that freezing effectively competes with other behaviors such as exploring and grooming. Freezing is also common in the passerine or song bird species. Curio (1975) notes that freezing is seen in response to a hunting sparrowhawk, as long as the hawk is far enough away that its presence does not elicit fleeing into the canopy. In veeries, Dilger (1956) describes the freezing crouch which is adopted instantly upon sight of a flying predator. The bird crouches close to the substrate, 18 the plumage is tightly compressed and the head may be retracted between the shoulders. The bird remains in this posture for two to three minutes without making any visible movement. Power (1966) describes a similar response in parakeets. If the flock is con- fronted with the sudden approach of a predator, the individuals crouch in a completely rigid, immobile state with the eyes open wide and the plumage compressed, and they may remain in this state for 15 minutes or more. Forsythe (1970) describes a similar postural pattern that occurs in response to distress calls of conspecific chicks of the long-billed curlew. In gallinaceous birds, freezing is a well known response in the nondomestic species. Stoddard (1931) says that a salient behavi- oral characteristic of the bobwhite is freezing to aerial predators. During freezing in aves, the bird's posture is characterized by a complete lack of movement, the plumage appears compressed, the eyes are wide open and the bird remains in the posture for a vari- able period of time. Stokes (1967) notes that the bobwhite chicks may freeze, or run for cover and then freeze for an hour or more, in response to either the appearance of a predator or to high pitched squeaks that resemble their distress signal. These descrip- tions are also found in works on closely related species. Freezing is similar in the California quail (Williams, 1969), the Gambel quail (Ellis & Stokes, 1966) and the chukar partridge (Stokes, 1961). Wood-Gush (1971) notes that freezing in the domestic fowl develops on day one in chicks to auditory stimuli and somewhat later to visual stimuli. Kruijt (1964) describes freezing of chicks of 19 the Burmese_red junglefowl as developing out of the squatting pos- ture in the first few days after hatching, and concurs with Wood- Gush that the bird freezes in the posture it happens to adopt at the moment of alarm. Freezing as a postural behavior pattern within aves appears to have common characteristics, to be involved in predator defense or survival responses of aves, and to be elicited by alerting or danger signals significant to the species involved. Accordingly, although a number of behaviors were examined in this dissertation research, the defensive response of freezing is of special interest. Habituation Studies Given the signal function of distress cries for conspecifics and also for members of other species, one might wonder whether habituation--response decrement with repeated presentations of a stimulus--would be observed in response to distress signals to the degree it is for reSponses to other types of signals. Habituation to distress cries in the rat was investigated by Zeiner and Peeke (1969, 1970) using a suppression technique for an innate response. Suppression of the drinking response to recordings of rat distress cries habituated over days, with the major decrement occurring over the first day. In six days of testing, habituation did not reach zero, primarily because the rats continued to orient to the distress stimulus. Freezing was the initial response to any novel stimulus. This tended to be followed by exploratory behavior such as rearing, which habituated over days. Using a pure tone of a 20 frequency approximating the dominant frequency of the distress cry stimulus produced more rapid and more complete habituation than that seen to the natural distress cry stimulus. Previous habituation to a pure tone had little effect on initial reSponsiveness to the dis- tress cry, but experience with the natural distress cry depressed subsequent response to the tone. Zeiner and Peeke suggest that a naturally occurring auditory stimulus presumably carries with it some additional information regarding aversiveness. For a review of habituation as a general psychological process, see Denny and Ratner (1970). Leibrecht (1972, 1974) pro- vides a comprehensive bibliogrpahy of habituation studies, including auditory studies. Hinde (1970) mentions that fear responses such as freezing typically are followed by avoidance behavior. If avoidance of the fear-producing stimulus is prevented, habituation occurs and the previously fear-producing stimulus loses its initial strength. Freezing and other defensive responses are replaced by exploration. Martin and Melvin (1964) investigated the fear responses of bobwhite quail to a silhouette model of a predator and to a live red-tailed hawk by flying these stimuli over a pen containing a single bobwhite. They ran two trials daily with a 3 minute ITI. Their total fear response consisted of: (l) a short run of less than 5 seconds, (2) stop and crouch and compress plumage, and (3) freezing or "immobility" for 10 to 13 minutes. As might be anticipated, the live hawk elicited the strongest responses, both in terms of freezing duration and of frequency of 21 crouch and escape behavior. On trial 1 of a live hawk presentation, seven of the nine birds exhibited a total fear response pattern, while only one bird in the silhouette condition showed this strong a response. Martin and Melvin found habituation occurring to both stimuli as well as faster habituation to the stimulus presented second. If the live hawk was presented first, it appeard to have a sensitizing effect similar to that noted in the Zeiner and Peeke studies just mentioned. That is, if the hawk were presented first, the response took about four days to habituate, whereas if the silhouette were presented first, habituation took only one or two days. Martin and Melvin's (1964) description of the short run part of the fear response sounds very much like the protean defensive display, which is a highly erratic, zigzagging flight in response to attack (Humphries and Driver, 1970). Bobwhites in the research reported in this paper exhibited similar behavior at the onset of an auditory distress signal. As Nice (1962) points out and as pilot work in the present study showed, an isolated bobwhite in an experimental apparatus is often an inactive animal. It would be interesting to see if the presence of conspecifics would lead to shorter or longer durations of inactivity, since Zajonc (1965) postulates that presence of con- specifics facilitates only the dominant response the individual makes in a situation. Melvin and Cloar (1969) presented a view of a live hawk in a chamber adjacent to a bobwhite quail key pecking for food. Ini- tially, the view of the perched hawk elicited strong freezing and 22 suppressed key pecking, but habituation to the hawk was rapid and showed no recovery after 18 days without presentation of the hawk stimulus. This study "unfairly" pitted freezing against key pecking. These birds were at 65% of their free feeding weight and had not eaten for 24 hours. While this may be a fine model for rat studies, it is not an appr0priate procedure for work with quail. These sub- jects were severely food deprived and 24 hours is a long hungry spell for an animal with the rapid metabolism of a quail. This same deprivation paradigm was also employed by Gardner and Melvin (1971) who presented a live hawk flapping its wings to quail feeding in an adjacent chamber. Using widely spaced trials (one daily), they found that the freezing response to the sight of the hawk habituated rapidly and by day 4 had reached zero responding. The results of these studies are in contrast to those of Curio (1975) in a study of organization of anti-predator behavior in the pied flycatcher. He found a lack of habituation when a live predator was presented under natural conditions, though mobbing habituated with stuffed dummies of a predator. However, it is diffi- cult to compare laboratory and field studies of this nature. It is possible that habituation to a predator in the laboratory may involve some stimulus-specific response decrement to the "circumstances" of the encounter. Whereas the constantly changing conditions of the encounters with a predator in the natural setting may dishabituate the response. Hinde (1961) comments that responses to novel stimuli, such as startle and orienting responses, are subject to rapid habitua- tion if not reinforced by further stimuli indicative of danger. The 23 rat literature on habituation of startle reSponses to auditory stimuli (see Davis, 1974, for review) certainly shows this phenomenon clearly. Hinde further suggests that responses to specific predators or danger signals such as the aerial alarm call of the chicken, are less likely to habituate than the general responses just mentioned. Frings and Frings (1968), in discussing the advantages of using alarm and distress signals for bioacoustic control purposes, also point out that natural signals have advantages over the use of synthetic noises. Two of the advantages they mention are that natural signals are effective at low intensities (as low as 3 dB above ambient level) and that habituation is much slower because these communication signals are part of the social structure of the bird populations. Boudreau (1968) also notes that sounds with a sharp onset or just general ”alert" noises that primarily elicit startle and orienting responses habituate rapidly and are ineffective if used alone in a bioacoustic control procedure. Many attempts at bioacoustic control of birds' behavior have failed. One possible reason for this was suggested to me by Johnny Stewart (personal communication). He speculated that one of the primary reasons novices had difficulty in calling predators with his distress signal recordings was that they jacked up the volume too high which renders the comunication value of the signal ineffec- tive. This high volume may produce enough distortion in the signal that it is experienced as a novel stimulus. Since novel stimuli habituate rapidly unless reinforced by other stimuli indicative of 24 danger (Hinde, 1961) anfl1high volume calls should also result in rapid habituation. Frings and Frings (1964) also emphasize that natural signals should not be presented at high volume levels or they lose their effectiveness in eliciting the appropriate responses. For this dissertation research, the question of interest is whether any habituation would be detected in a laboratory situation over three repetitions of an auditory signal to groups each of which heard a different type of signal. Bobwhite uail Colinus vir inianus as a Preparation Natural history and observational reports on the bobwhite quail (Colinus virginianus) recommend it as an excellent preparation for the study of many of the major classes of consummatory behaviors. In addition to being one of the most popular of the upland game birds of widespread distribution throughout the United States, its varied and distinctive repertoire of social behaviors offers a challenge to our understanding of the behavior of a nondomestic member of the galliformes. It is also a useful laboratory preparation for the study of defensive responses to predators in a social species that exhibits a wide repertoire of behaviors under confinement conditions. Colinus virginianus is a small variegated brown, black, and buff colored precocial galliforme, native to the United States, which shows cryptic coloration in its habitat. One of the striking aspects of a quail family or a quail covey' (a collection of quail larger than a family) is their highly integrated group behavior 25 (Nice, 1962). The group appears to act in concert as a unit, par- ticularly with regard to daily activities such as preening, dusting, feeding, resting, and predator defense patterns. A typical observa- tion by Stoddard (1931) illustrated predator defense. . . . alarm causes every bird to freeze and remain absolutely motionless for periods of seconds or minutes, when suddenly, as if at a given signal . . . all relax and go about their business (p. 18). The primary sources of general information on the bobwhite are Stoddard's (1931) classic text on the habits and preservation of the bobwhite, Johnsgard's (1973) Grouse and Quails of North America, and Stokes' (1967) three—year study of the behavior of this bird. These sources agree that one of the outstanding and prepotent responses in the repertoire of the bobwhite is the freezing response to an alerting stimulus, particularly a source of alarm. Another attribute of this species that should be pointed out is that it is continually subject to significant predation from aerial predators whose visual search for prey is often dependent on prey movement of a cryptically-colored species. Denny and Ratner (1970) list freezing as one of the most obvious examples of predator defense. vAlcock (1975) also points out that hiding from enemies is generally achieved through cryptic coloration and behavior such as freezing. The behavioral aspects of camouflage include more than the ability to remain motionless, although the effectiveness of camouflage is dependent on freezing. An animal will blend into the background only if it has chosen the proper substrate. There is also an appro- priate time to freeze and this may be dependent upon the distance 26 between the predator and the prey animal as suggested by Ratner's (1967) defensive distance model. Many camouflaged animals remain motionless until the last possible moment and then suddenly dash away, exhibiting the protean or variable defensive behavior pattern described earlier (Humphreis & Driver, 1970). This is a highly erratic, zigzagging response to any attack, a behavior pattern which is common in quail before the defensive distance is reduced to zero. Robinson (1969) reminds us that freezing following locomotion is probably of great importance, since movement may have concentrated the attention of the predator on the area in which the animal has come to rest and subsequent movement might be fatal. In addition to the effect of predator prey-distance, the nature of the defensive response may be dependent upon the nature of the alerting stimulus. Worden and Galambos (1970) note that the operation of feature detec- tors differs for different sensory systems, suggesting that a visual stimulus may be responded to differently than an auditory stimulus. Bobwhite quail thus have a number of attributes which make them well suited as experimental animals for the present study. They have a rich and readily observed behavioral repertoire, including in particular a readily elicited defensive freezing response. They have the further advantage over the more common laboratory animals in not having undergone generations of domestication as laboratory animals, so their behaviors may more closely resemble those of animals in the wild. 27 Pilot Work Because there was no model or paradigm for the planned research available in the literature, considerable pilot work was carried out to test the feasibility of the main study. Pilot work first suggested the necessity of exposing the subjects to the experi- mental apparatus prior to running test trials. Without prior expos- ure to familiarize them with the chamber, birds sometimes remained immobile for periods as long as hours, making it impossible to observe any responses to test stimuli. Accordingly, a chamber habituation procedure was instituted for all groups of birds. In the pilot study, nine independent groups of bobwhite quail, in triads of one female and two males who were housed together, were observed for their repertoire of responses under the following stimulus signal conditions: Bobwhite quail distress signal, chicken distress signal, blue jay distress signal, rabbit distress signal, a goshawk vocalization, reversed bobwhite quail distress signal, bobwhite quail food call, 4 K2 pure tone signal and a taped silence (tape hiss) condition in which no other specific signal was presented. The procedure followed was first to provide habituation sessions as described in Chapter Two. Briefly, subjects were placed in the experimental chamber until they met a predetermined activity criterion (see page 58 for full description of this procedure). Following habituation sessions, all groups first experienced a 6 minute base- line period in the chamber with no signals presented. If they met an activity criterion (defined full in Chapter Two, Method) they were 28 run through one set of stimulus signals consisting of three presenta- tions of the signal with a 2-minute intertrial interval. The data of interest were the changes in behavior patterns going from the baseline to the call-signal situation. The important differences and changes found can be summarized as follows: (1) Freezing was minimal to nonexistent during all 6-minute baseline periods. Following this baseline period, freezing duration in seconds decreased in the following order: Bobwhite quail distress call (48 sec.), chicken (24 sec.), blue jay (21 sec.), pure tones (15 sec.), reversed bobwhite quail distress call (8 sec.), and goshawk vocalization ( 2 sec.). Taped silence, bobwhite quail food call, and rabbit distress call all elicited zero freezing. These results suggested that the distress signals were having differ- ential effects on the experimental birds and that freezing was an appropriate measure of defensive responding. (2) Duration of dust- ing behavior increased in magnitude from baseline to test signal period for most groups. Exceptions were the bobwhite quail distress groups and the pure tone signal groups, where dusting durations remained low and stable. A decrease'h1dusting among groups hearing the chicken and blue jay distress calls suggested that the signal had a suppressive effect on this response. Dusting seemed to me an especially useful baseline indicator that these birds had become somewhat comfortable in the test apparatus during habituation to it. All of the birds had experienced dusting as chicks, and as adults all of the subjects were exposed to dusting in the chamber, but they 29 did not have dust available in their home cages. When they dis- covered the dust box in the chamber, it was a powerful elicitor. Many of the birds began dusting within a few minutes after entering the chamber and continued to dust intermittently for an hour or more if left in the chamber undisturbed. The birds would often return to dusting immediately following a disturbance--a noteworthy effect, for anything that interrupts or suppresses dusting has to be a fairly powerful stimulus for dust-deprived birds. Other pilot study results are cited in later sections as relevant to the definition of response measures and scoring cate- gories. Aims and Purposes of This Study The present study was designed to provide information rele- vant to the issues stated below: 1. Birds have natural defensive responses to alerting signals. One emphasis of the project is to assess the effect of auditory distress signals in the bobwhite quail. (a) What are the responses to a distress call in this species? (b) Does a distress call signal elicit defensive responses and supress nondefensive responses in this species. Experimental Hypothesis 1: Distress calls elicit defensive responses and inhibit nondefensive responses in bobwhite quail. 2. It is conceivable that distress vocalizations are not necessaribly species-specific, e.g., that a scream is a scream in any language. Does the species-specific distress vocalization 30 function to elicit defensive responses only in conspecifics, or are these signals also effective for other members of the habitat, closely related species, and distantly related species? Experimental Hypothesis 2a: The conspecific distress vocali- zation is the most effective stimulus; in particular it will elicit a defensive response, freezing, in greater magnitude than distress vocalizations from other species. Experimental Hypothesis 2b: The closer the evolutionary rela- tionship between the species, the more effective the dis- tress signal as an elicitor of freezing. The magnitude of freezing in the experimental groups decreases roughly in the following species order: Bobwhite quail, chicken, blue jay, rabbit. 3. A general psychological phenomenon, habituation, typically shows up as the decrement of a response after repeated presentations of a stimulus. 00 natural defensive responses (such as freezing) to efficient elicitors (such as distress signals) also habituate? Since available data on this issue are equivocal, we will make a null hypothesis. Experimental Hypothesis 3: No significant habituation is obserVéd’in any signal condition. 4. Distress calls of different species have not been com- pared spectrographically. Measurements from a spectrographic analy- sis of the distress signals employed as stimuli in the present study will be made and described. METHOD To test the experimental hypotheses, two studies were con- ducted as outlined in Table 1. In both studies, triads of bobwhite quail were first habituated to the experimental chamber, then placed in the chamber for a six-minute behavioral baseline period follow- ing which they were exposed to the experimental stimuli. In Study 1, which was designed to examine reSponses to the conspecific distress call (Hypothesis 1), independent groups of six triads of birds each heard either bobwhite quail distress calls or a taped silence con- trol. In Study 2, which was designed to compare reSponses to dis- tress calls of different species (Hypotheses 2a and 2b) independent groups of five triads of birds each heard either one of the four distress calls or one of two control stimuli. Habituation (Hypo- thesis 3) was examined by comparing responses across the three stimulus presentations in Phase 3 of Study 2 (see Table 1). Since method and procedure were much the same for both Studies 1 and 2, the following discussion applies to both studies unless one of the studies is specifically designated. Subjects Bobwhite quail (Colinus virginianus) was the species chosen for study, for the reasons outlined in Chapter 1. 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U if ::0 J ;. :1. 5:5 ‘ .;. Pecking Dusting Proximity Locomotion Vocali- zation BEHAVIOUR CATEGORIES 73 bobwhite distress signal subjects. This same pattern is observed for vocalization. This possibly reflects the influence of the food call signal which often elicits approach and other socially facili- tated behaviors such as vocalization. This may also account for the increase in the proximity mentioned above. It is not possible to draw a clear conclusion about this in the present study. Study 2 Study 2 was designed to test two experimental predictions: 1. The conspecific distress vocalization is the most effective response stimulus; in particular, this signal elicits a defensive response, freezing, in greater magnitude than distress vocalizations from other species. 2. The closer the phylogenetic relationship between the species, the more effective the distress signal is as an elicitor of freezing. Thus, it was predicted that the magnitude of freezing in the experimental groups decreases roughly in the following order: bob- white quail, chicken, blue jay, rabbit. The reversed bobwhite dis- tress call and the bobwhite quail food call were considered control conditions. The ANOVA test paradigm and data procedure for Study 2 are the same as for Study 1. In Study 2 we have six signal conditions; 5 cages or triads of subjects in each signal condition, and 2 observations (baseline and signal period) on each cage of birds. Thus, the baseline-signal period functions here also as the repeated 74 measures test in this analysis. This analysis gives a conservative test for the same reasons as in Study 1, namely inclusion of the food call signal common to all experimental groups and inclusion of any habituation effects which might have occurred over the three trials of signal presentation (and, as we shall see, there was sig- nificant habituation of some response categories). Since the freezing response pattern is again of major inter- est here, the full ANOVA summary table for freezing follows (Table 6). Table 6 shows that while freezing is not differentially elicited by the different signal conditions (main effect F < 1) the signal period is clearly different from the baseline period (F = 76.04, df = l, 24, p < .001). The predicted signal X test period interaction was not statistically significant in this analysis. The ANOVA for freeze/Head is almost identical to that shown in Table 6. Full ANOVA tables for each dependent variable are available in Appendix B. The significant test effect showing distress signals to be efficient elicitors of the defensive pattern of freezing is dramati- cally illustrated in Figure 4. This figure shows data on the freez- ing and freeze/Head behavior categories across all six signal conditions for both the baseline and signal period. The clear elicitation of freezing above baseline during the signal period follows the predicted magnitude order within aves. The conspecific distress signal elicits the greatest amount of freezing, followed by chicken and blue jay respectively. This order also follows for the 75 TABLE 6.--Analysis of Variance of the Freezing Response in Bobwhite Quail During Baseline and Signal Test Periods with Inde- pendent Groups Assigned to One of Six Signal Conditons: Bobwhite Quail Distress Call, Bluejay Distress Call, Rabbit Distress Call, Chicken Distress Call, Reversed Bobwhite Quail Distress Call, and Bobwhite Quail Food Call Source SS df MS F Total 228.86 59 Between Cages 79.56 29 Signal Conditions 8.46 5 1.69 < 1 Error (b) 70.69 24 2.94 Within cages 149.70 30 Test periods 107.68 1 107.68 76.04* Signals x tests 8.03 5 1.61 1.13 Error (w) 33.99 24 1.42 *p < .001 76 .Poo. v a .cowuwccou Pmcmwm op m:w_mmmn Eoee zpucmumecmwm umcoewwu mmwgommumu cow>msmn spam .mucm2m>os new; mpamuumuou mew mews“ “an mpwnoeew mm xuon m.vcwn use mews: .mpcm5m>oe new; saw: mewNmmge eo mucmu -wucw mmumcumappw cameo em3o_ on» .zuwpwaossw ppzm mw gums: toe :owcmpwgu ms» .mchmmge szm eo mucmumucw mzozm :qmem some: use .mapaempm agopwuzm acmemwmwu m team; sows: eo some mugwa mo masocm xwm Low meowcma cowumucmmmgn Pmcmwm lemon ecu mcwpmmmn Pmcm_m1mca mcwgzu meza mgmszaom we mmmcoamws newnwmcw cam: é 8:3“. 77 __au mmutum_o coca «pagzaom muwzznom omem>m¢ chmwmiumOg mcwpmmmn chmwmimca masomw zcmhuazou 4mm “wanna xmw mzpm :mxuwgu muwsznom .v 0 .1 _ M H a? VH0"... . 00 .. “Hun v 9 A .9 9 . .9 9 .90 méa FL ax rIL L x.“ a. x. 3 a.“ a.“ v9... .999. x.“ 3 .000. .000. .000. L .000. L 0099. . 99c .99 O O O .9 .0 '0'0 030: .9 .¢ 9 o .v d chmwmuumoa mcwpmmmn chmwmimem SHSNOdSBd NVEH 85 stressful situation might increase contacting responses in this spe- cies in the experimental chamber. As shown in Table 7 and illus- trated in Fig. 7, the signal conditions elicited proximity responses significantly above baseline levels, F = 21.43, df = l, 13, p < .001. This repeats the finding in Study 1 that proximity responses increased significantly from baseline to signal test and that it is a frequently observed behavior pattern in the test chamber under all conditions. Proximity responses might be expected to be high during food call signals because of the approach response and social facili- tation properties of this stimulus, as previously discussed. Locomotion reflects basically the amount of motor activity in the chamber in ways that serve to move the bird from one location to another, typically by walking. Since there was no cover or place of concealment offered within the chamber, and locomotion is mutually exclusive of freezing, it was expected that this behavior pattern would be suppressed by the signals. Fig. 8 illustrates the signifi- cant decrease from baseline to signal period across the signal condi- tions, F = 7.96, df = 1, 24, p < .01. The pattern here is generally one of less locomotion follow- ing the baseline period with the exception of the blue jay signal condition which showed no change. In this behavior category, both the reverse and food call suppress this behavior more than the blue jay distress call. Locomote/Contact, scored only when a bird made a definite approach to another bird, did not mimic the locomotion pattern of 86 .moowcoo ocwpomoo cos» Focmwmiumoo moweoo Apoo. v av Looooom xpucoommwomwm mo: humswxoco .mcowp_o:oo chmwm agopwooo xwm Lo :ooo op moowgoo Amcoo omsouogv poomwmuumoo oco Ameoo cooov ocwpomoo Foco_m-oco mc_goo Fwooo ouwgzoom mo momooomoe mowewxooo coo: K 85o: 87 macaw onHHmzou 4oo oopm coxowgo mowszoom ouwszoom omgo>oz 0000. .000. .000. .00 . 0000. .000. . 00. .0 00. 0 9 . 9 9 . 9 0 v 9 . 00 .0. .0 00 0000. . 0 0000. .000. U 9999. .9N9“ .99 99. 09 9 9. ed a? .33 at 0000. . 00. .0000. .000. 0999. 9 9 _ 9 0. 0 9 . . O . 9 . .9 9 9 9 U 0999. .999. 9 9999. 0999. . 0 . 0 0 .000. 0 . 0 . .000. 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"0N0“ 0 0 '9 . . . mcwpmmmn PmccwmiwLa [I m «- SBSNOdSBU NV3H Ln £5 C3 01 88 .moowgoo Foomwm coco oowpomoo mcwcoo Apo. v ov goooocm xpuomowemcmwm mo: oovpoEoooo .mcowuwoooo Foomwm xgouwooo xwm eo zoom ow moowcoo Amgoo oonouozv Pocmvmiumoo oco Amcmo cooov mow—ammo poom_m1oeo mcwgoo Pwooo ouwgzoom eo momooomoc cowoosooop coo: .m 8.6.: 89 __ao oooa mo.;zaom mmocumwo ao_;zaom omoo>om ozom¢ zcfihmazcu 4¢zomm mmogom_o mmocamwo mmocomw: p.22aa see o=_m coxo.;o mmotumwo mu_;Zaom C ’. A .. 9 9 A '9 9 9 A 9 9 9 .A '9 .9 A .9 A 9 9 9 A 9 30 A 9 9 A 9 9 9 .. &. pooowm-umoo ocwpomoo,Fo:m_m1ouo o.— m.~ o.m m.N o.m SHSNOdSBU NVEW 9O responding. It was for this reason that it was initially designated as a separate behavior category. Consistent with the finding in Study 1, locomote/contact showed no significant effect in Study 2. As can be seen in Table 7, however, both the baseline to signal and the interaction effect approached significance with the pattern of results more closely resembling those for proximity than those for locomotion without contact. Vocalization included any audible signal given by a bird during testing. Frequently, it was impossible to determine which bird produced the sound, with the result that frequently more than one observer scored a response in this category when only one bird was actually vocalizing. This may in part account for the apparent high frequency of this behavior category relative to the other measured behavior patterns. However, bobwhite do vocalize frequently when they are together in a unit. As Fig. 9 displays, there was a significant decrease in vocalization from baseline to signal period, F = 19.17, df = 1, 24, p < .001. This was in the predicted direction for all the signal conditions except the conspecific distress call. During presentation of the bobwhite distress call signal vocaliza- tion responses increased slightly from baseline. As shown in Table 7, the interaction, signal x test, was a significant effect, F = 2.78, df = 5, 24, p < .05. Cautious Posture is a pattern most often seen when a bird is approaching something novel. It is also sometimes observed briefly in a group of bobwhite when they first break from a freeze. The 91 .Amo. v no Paco.m to 0a». cow: z—uooowewomwm oooootoucw ooweoo ammo ooo .A_oo. v av moowgoo ocwpomoo coop Poomwm mowgoo mmop apoooovewcmwm mm: cowooNVPooo> .mcowuwoooo Foomwm xgouwooo xwm wo zoom op moomgoo Ameoo oocoponv Pocmmmupmoo oco Amgoo cooov woe—omen Focmwmumco newcoo pwooo oumnzoom eo momcoomog :owponpooo> cmmzuu.m meomwu 92 3????099¥?“’ A3A3A3AOA.A.A.A.A.A Food Bobwhite Call 00000000000000000000 99999999 9 9 9 9 9 9.9.9.9 ............. Reverse C.) C 0000000 .P .000000 ,_ 9.303030303030300 (D on (U a f F l— (U (U C I: U! C : 'v- ‘l- W m 1 i +4 (D U! I. O (L O. Bobwhite Distress '0'9'0'0'0'0'0'0'0'0'0'0'0‘0' 000000000000 ~838$§§§5$§3§AA 13ml 03A3A3A3A3A3A3A3A3A3A3A3A3A3A3A3A3A3A3 Rabbit Distress .9.9.9.9.9.9.9.9‘9‘9‘9‘9.9‘9‘9‘9‘9‘9‘9‘9‘9.9‘9‘9‘9‘9.9 9 9 9 9 9 9.9.9.9...9.9.' A3A3A3A3A3A3A A A A A A A A A A A Blue Jay .Distress SIGNAL CONDITION GROUP 99999999999999 -vvvv9vvv 9999999 000000000 0000000000 999%flhflfifl gagfiQ§§Qfiafiaavvvvvvvvvvve0 0.0.0.0.0-0.0.0.0.0.0-0.0.0.0-0.0.0.0-0-0.0.0.0_0.0.0.0. Chicken Distress 0'0'0'0'0'0'0'0'0'0'0'0'0‘0'0'0‘0'0'00 .02o30202020202020202020320202.2929}:0. r l .l I I l a) RED Ln SBSNOdSBU NVHH Ill” 10 u- 9 Bobwhite Distress 93 present data suggest that is is an infrequent behavior pattern when no visual novelty elicits it. In Study 1, this behavior increased from baseline to signal, but the data only approached significance, p < .10. In Study 2, an increase from baseline to signal was observed again in the bobwhite distress call signal group condition; the mean response rose from .4 to .9. The means for the other groups are also of this general magnitude and show no consistent pattern of directional change. Given the low frequency and small variation of the behavior pattern in this test significant effects would not be expected and were not obtained, as shown in Table 7. The same comments regarding low frequency and behavioral variation obtain for the gular quiver category. The twelve means there range from .03 to .73, though the differences are not significant. Gular quivers decreased from baseline for all the signal groups except the bob- white reverse distress signal, which increased. Study 2 Habituation The third experimental hypothesis: No habituation occurs in any signal condition, was tested using the same two factored repeated measures ANOVA used in the previous studies. To examine the data for habituation, however, each trial presentation of the stimulus signal was examined separately. For this analysis we have again six signal conditions, five cages or triads in each condition, and three observations or trials on each cage of subjects. These trials are referred to as l, 2, and 3 successively in the figures. In this analysis the responding during the food call period, common 94 across all signal conditions, was not included; only responding to each presentation of the experimental stimulus was examined. Behav- ior during food call presentation will be treated subsequently in a separate analysis. Only those behavior categories that produced a significant effect in a previous analysis were analyzed here. The primary question of interest is whether a response decrement is observed over repeated presentations of the stimulus signal. The available data in previous literature on natural defense responses (such as freezing) habituating to efficient elici- tors (such as distress signals) are equivocal. It has been demon- strated in the present studies that distress signals do indeed function as powerful elicitors of the freezing response pattern in these animals even under laboratory conditions. Since freezing has consistently shown up to be significantly influenced by the present experimental manipulations, we will begin the analysis of habituation with this response pattern. The ANOVA table for the freeze response follows as Table 8. As shown in Table 8, the null hypothesis of no habituation can be firmly rejected since the trials effect was significant. Figure 10 illustrates this effect for both the freeze and the freeze/ Head responses, over all six signal conditions. The largest drop in responding clearly occurs from trial 1 to trial 2 in all the distress signal conditions. The only signal condition not showing a response decrement across trials is the food call condition. This is to be expected if the food call is serving as a control condition which elicits little defensive responding in the first place. 95 TABLE 8.--Analysis of Variance of Incidence of Habituation of Freezing Responses over Three Signal Repetitions for Six Independent Groups of Bobwhite Quail Assigned to One of the Following Stimulus Signal Conditions; Bobwhite quail Distress Call, Chicken Distress Call, Blue Jay Distress Call, Rabbit Distress Call, Reversed Bobwhite Quail Distress Call, and Food Signal Control Call Source SS df MS F Total 28119.29 89 Between cages 15973.29 29 Signal conditions 2029.55 5 405.91 < 1 Error (b) 13943.73 24 580.99 Within cages 12146.00 60 Trials 2669.49 2 1334.74 8.17* Signals x Trials 1633.04 10 163.30 < 1 Error (w) 7843.47 48 163.40 *p < .005 96 Figure 10. Habituation analysis: Mean defensive freezing responses per interval over three repeated experimental auditory signals (trials 1, 2, 3) showing significant habituation (p < .005, both analyses). 12 11 DEAN RESPONSES/INTERVAL 10 97 FREEZING “l rf'ln 123 Bobwhite Distress p1 fl _. '1 FREEZE/HEAD 123 123 7123 51253 Reverse Chicken Blue Jay Rabbit Bobwhite Distress Distress Distress Distress SIGNAL CONDITION GROUPS BY TRIALS l 2 3 Bobwhite Food Call 98 Another interesting feature of Fig. 10 is that the extent of trial 1 responding follows the order of decreasing magnitude of freezing predicted in experimental prediction 2b. That is, the closer the phylogenetic relationship between the species, the more effective the distress signal will be as an elicitor of freezing. Also, the mean total responses over the 6 minutes follows the hypo— thesis for the avian species; the rabbit call (which seems to show less habituation) falls in the middle, as does the bobwhite reverse call. This confirms the similar observation made in Fig. 4. The present data, Fig. 10, demonstrate that the obtained change in freezing can be attributed to the behavior of the birds during the actual distress signal presentation period. That is, the effect is more striking when responding to the common food call section of the stimulus tape is subtracted out of the data. Table 9 summarizes the ANOVA results on the dependent meas- ures analyzed for habituation in the present study. The tabled p value for each effect for each behavior category is shown. The complete ANOVA tables for this analysis are available in Appendix 0. Only those behavior categories showing significant effects or strong trends in this analysis will be graphed in the following figures. Fig. 11 illustrates the mean pecking and dusting responses to repeated presentations of the auditory stimulus over all the signal conditions in Study 2. As shown in Table 9, none of these effects were statistically significant though there were several interesting trends. Figure 11. 99 Habituation analysis: Mean pecking and dusting responses (responses per interval) of Bobwhite quail over three repetitions of auditory signals (trials 1, 2, 3). Differ- ences showedatrend in the predicted direction (p < .20, all effects, dusting, p < .20, trials, pecking). See Table 9. 1m 5’ H pec ING Fl '" K. A HJ NWT .1 Al“ 1 3 F __ r— ’ '1 "‘ "1l—l 2 D 2" N. > a: La] EEO \ m e e 8? a: "Th-1 F“ g 4L DUSTING .4 L 3 v- _ JPN 2 h- 1-j7 or 7 , , , - l 2 3 l 2 :3 l 2 3 l 2 3 l 2 3 l 2h3 Bobwhite Chicken Blue Jay Rabbit 0:51:51: 80230;” Distress Distress Distress Distress Distress Call SIGNAL CONDITION GROUPS BY TRIALS 101 TABLE 9.--Analysis of Variance Results Summarized for Those Behavior Categories that were Statistically Significant in Study 2. Data are Presented from Six Signal Conditions over Three Trials of Signal Presntations of Each Signal Condition Behavior Category Signal Condition Trials Signal x Trial Pecking ns .20 ns Dusting .20 .20 .20 Freeze ns .005 ns Freeze/Head ns .005 ns Proximity ns ns ns Cautious Posture .20 .025 ns Locomotion ns ns ns Vocalization .20 .10 ns 102 In contrast to the defensive behaviors, pecking and dusting behaviors do not show response decrement over three trials for any of the distress signal conditions. Competing, mutually exclusive patterns hardly could show this decrement if freezing was signifi- cant. The real question, then, is, was there a significant increase over trials? The food call signal group shows a slight decrement across trials for the category of dusting, as might be expected of a control condition. This is not to say that habituation as a process is not illustrated in these data. For both pecking and dusting, several of the signal conditions show an increase over trials in the distress signal conditions. This appears to reflect that the birds are increasingly engaging in these behaviors following the effect of the first signal. That is, this is the reverse of the freezing data in Fig. 10. This confirms the effect found in the previous analysis of pecking, illustrated in Fig. 5, that pecking is suppressed by the signal presentation. The present analysis points up how the distress signals were suppressing pecking, especially on the first trail of hearing the distress signal. Following this initial suppression, in most instances, the response increases at least by the third trial. The behavior category of dusting shows a similar pattern to pecking over most of the distress signal conditions. Fig. 12 displays the same analysis for the behavior cate- gories of cautious posture and vocalization. The cautious posture Figure 12. 103 Habituation analysis: Mean cautious posture responses and vocalization responses (responses per interval) of Bobwhite quail over three repeated auditory signals (trials 1, 2, 3). Habituation was present in both response measures (p < .025, cautious posture: p < .10, vocalization). MEAN RESPONSES/INTERVAL 104 0 p _ CAUTIOUS POSTURE .5" .0" .5" C IL,— , l ll 9f VOCALIZATION '1 F1 81- — lei-1 7 1- WM 6.. Pi - 5 F'l__ r a 4.. _q _. 3- '7 2 1- “ r- gt:fi l 2 3 l 2 3 l 2 3 l 2 3 l 2 3 l 2 3 . . Bob hite Bobwhite Chicken Blue Jay Rabbit gggggzie F30, Distress Distress Distress Distress Distress Call SIGNAL CONDITION GROUPS BY TRIALS 105 behavior category clearly shows a significant response decrement across trials (F = 4.59, df = 2, 48, p < .025). The rabbit distress call did not contribute to this effect; there is an unmistakeable floor effect. The difference between signal groups only approaches significance, F = 1.79, df = 5. 24, p < .20. Vocalization, the bottom section of Fig. 12, generally shows response decrement over trials for all the distress signal conditions. The food call condition shows only minimal change over the three trials, as might be anticipated for the control condition. This elaborates on the finding in Study 1 that vocalization decreases under the bobwhite distress signal condition. It also confirms the finding in the earlier analysis of Study 2 that vocalization is high under both baseline and signal tests for the bobwhite distress sig- nal condition,shows a significant change from baseline to signal condition, and is differentially affected by the signal conditions (interaction, signal x test, p < .05). Vocalization is generally high in the aves signal groups, and shows a decrement following the first trial. Again, we notice the pattern shown earlier that responding to the rabbit distress signal condition differs from the avian signal conditions. Study 2 Food Call vs. Trial 1 of Test Signal Each signal condition stimulus tape initially presented one trial of the bobwhite food call vocalization immediately following the baseline period and preceding the signal condition stimulus. 106 (See Fig. l, p. 49.) Thus, all the birds had one trial of a non- experimental auditory stimuls onset in the chamber before the test signal was presented. The results analyzed prior to the habituation analysis always included this common food call period as part of the data during the signal period as a conservative test of the experi- mental predictions. In addition, habituation was clearly shown to many of the tested signals, suggesting that Trial 1 responses provide the clearest test of any effects of signal conditions. It is of some interest then to examine separately changes in responding on Trial 1 only in comparison with this common food call period. An ANOVA was prepared for each behavior category that had shown a significant result in previous analysis. In this analysis we again have six signal conditions, two tests (food call vs. trial one) and five cages in each observation. The full ANOVA summary table for freezing follows. The results shown in Table 10 for the freezing response ANOVA are essentially duplicated in the freeze/Head behavior cate- gory ANOVA. All ANOVA tables for this analysis are available in Appendix E. Figure 13 illustrates the pattern of responding for both the freeze and freeze/Head behavior categories over the six signal con- ditions. In examining this figure, it is immediately apparent that the onset of an auditory stimulus does elicit some freezing behavior in these birds in the chamber. It is also clear that the particular stimulus signal in each distress signal condition elicits freezing 107 TABLE lO.-1Analysis of Variance of the Freezing Response in the Bobwhite Quail under Six Signal Conditions Testing Responding to the Common Bobwhite Food Call versus Responding to Trial One of the Experimental Stimulus Signal. Each Triad Score Constitutes One Unit for Analysis Source SS df ms f Total 24926.50 59 Between cages 19517.50 29 Signal condition 2755.70 5 551.14 < 1 Error (b) 16761.80 24 698.41 Within cages 5409.00 30 Test (FC vs. Tl) 1480.17 1 1480.17 11.42* Signal x Test 819.43 5 163.89 1.26 Error (w) 3109.40 24 129.56 *p < .005 Figure 13. 108 Mean defensive freezing responses for a food call signal (open bars) to the first experimental signal, Trial 1 (dotted bars). 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AmN.NV oo.N Am... V mo.m Aeo.NV No.A N m=.om=o me. V AN. ANN. V Ne. MAN. No. ANN. «N. NN. w on. MAN. on. m Nm. V om. A.¢.NV Ao.. Am. AN. ANN. NN. Nm. he. NN. AN. m o=A=ooea NN.AV oo.m A...A oN.m MmN.N No.o AoN.N mo.m ANN.N m... oo.NV NN.o m N..AV N_.N Am_.A oo.m oN.N NN.N AN... oN.o Aom.N NN.o oA.NV Na.m N oc.xoo. AoV .w AoV A. AoV .w AoV .w AoV .m AoV .w . 9:53: AA~o coo. omcosoa o_ana¢ A.» osAm eoxo.;o oSAAzaom A. Assam--oomoh AmV oo..o. pogo.m 0:. AmV oc..omom o=_c=o aco.o.o=oo Aaco.m x.m Lo. AoV aco.oa.>oo oaooeaom 0:. menu: co o_.oh--._-o NANu¢ mapzzaom + 95.. mmmgum.o mu.c:aom 111-- _ _ _ 8m 8. Q can mAaum mucouo.....z mu.o> z ...u woo. o..::ao. i wEwH _ fl. _ ocN oo. . mpmum MUCOUQmF—pwz 11 :1 *1 lw 1E brl s. . «~41 ‘0‘ 5 fi . ' I, I II! Il‘l' III. .. I" ‘v Lam ouwo> mmmgum.o :mxu.zu v-1 . I Ihuhllul'l‘all 3. V I]. A 1415.119 111. 11111l 1.1 ',|I .5. I! 01.01--. IIIII! . i-‘ I p 4 V A .. pr V . _ . . I v -. .AOm . 3536‘ - aaegafihna (III-1'61!“ 65%-: o’---‘ .1. "I'la . 3235 saw 2.5 + 3283225 8...» 30.5.5 :22 V1_1|_ 8N oo_. 0 11-111-.. . .1 . m—wuw mucoumeZz o u 11...- .1- ...1.- -1. 15.... 1:31..-.11 _ I! . . . .i .-. 1.. N 1--.-..u......., . - .1...::-. - . ...... 165 REFERENCES 166 REFERENCES Alcock, J. Animal behavior. Sunderland, Mass.: Sinauer Association, Inc., 1975. Altmann, J. Observational study of behaviour: sampling methods. Behaviour, 1974, 42, 227-267. Armstrong, E. A. The ethology of bird display and behavior. New York: Dover Publications, Inc., 1965. Beer, C. C. Individual recognition of voice in the social behavior of birds. In D. S. Lehrman, R. A. Hinde, & E. Shaw (Eds.), Advances in the study of behavior, 1970, 3, 27-74. Bent, A. C. Life histories of North American raptors. New York: Dover Publications, 1963. Best, Catherine T. The role of consonant and vowel acoustics features in infant cerebral asymmetrics for speech perception. (Ph.D. dissertation, Michigan State University, 1978). Bolles, R. 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