There is a long history of studying bird interactions with agriculture. The field of economic ornithology, which looked at the positive and negative aspects of birds in agricultural, was popular at the end of the 19th century. However, the field quickly fell into disrepair. Today, we once again recognize that birds can provide both services and disservices to agriculture. The balance of services and disservices that birds can provide depends on many factors, such as the species found in the crop, the crop in question, and other factors such as surrounding landcover. Many of these factors are currently being disentangled in this rapidly evolving area of research. To understand how birds interact with crops, we first need to know more about the species that use different crops. In Chapter 1 I characterized the different species that use sweet cherry orchards, blueberry fields, 'Honeycrisp' apple orchards, and vineyards in three major fruit growing regions during the early 2010s. I also determined the abundance of fruit-consuming birds found in each crop and investigated which fruit-eating species could be considered important fruit consumers based on their frequency of detection and fruit consuming habits. I also examined if the heterogeneity of the surrounding landcover influenced the abundance of birds found in the various fruit fields/orchards. I found that the abundance of fruit-eating birds varied by both region and crop, as did which species were designated as important fruit consumers. However, abundance was not influenced by the heterogeneity of the surrounding landcover, counter to our predictions. Certain species of birds are known to be beneficial in agricultural areas. Birds of prey are of particular interest, as they can deter vertebrate pests. In Chapter 2, I investigated the effectiveness of installing nest boxes in attracting American Kestrels to blueberry growing operations in Western Michigan. I then compared the results with a similar study where nest boxes were used to attract kestrels to sweet cherry orchards in Northern Michigan. By installing nest boxes and performing survey transects, I found that boxes did increase the overall presence of kestrel in blueberry fields, although the effect was much weaker than in the sweet cherry study. Nest box occupancy was much lower in the blueberry system when compared to the sweet cherry study region, but reproductive success measures, such as mean clutch size, were similar. While birds of prey have been documented consuming and deterring fruit-eating birds, they may consumer/deter other species of birds as well. In Chapter 3 I investigated the effect of American kestrel presence on bird abundances in blueberry fields in Western Michigan. I found that active American kestrel boxes did not deter fruit-eating birds from blueberry fields. However, active boxes did deter non-fruit-eating birds, although this trend only held when the box was active. This finding introduces the possibility that kestrels might deter beneficial insectivorous birds, which could be detrimental to the blueberry fields. Through my work, I have found that the effect that birds will have on a particular agricultural system will be highly context dependent. The mixture of bird species present, the crop type, region, and many other factors will influence how birds fit into an agroecosystem. Introducing predators to control for pests could induce a trophic cascade with positive or negative outcomes. Predicting the nature of the outcome will require intensive studies of the crop in question, with knowledge of the bird and arthropod community in the region.
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