"Agricultural crops provide foods that attract a variety of foragers. In particular, fruit crops 9 attract many fruit eating bird species because fruits are densely available, energy-rich, and 10 readily accessible. Agricultural systems have important implications for avian foraging because 11 they manipulate the availability and quality of food. Avian fruit orchard use and crop 12 consumption represent a major conflict between humans and wild birds. Despite nearly a century 13 of attention paid to understanding the nature of this conflict, many inconsistencies and avenues 14 for research remain. In this dissertation, I utilized a variety of techniques including radio 15 tracking, focal observation, and bioenergetic modeling to understand more fully where, how, and 16 to what extent wild fruit eating birds use cultivated fruit resources in northwest Michigan, as well 17 resulting implications for crop producers. Species-specific information on crop damage and 18 habitat use is essential for better-informed pest management programs and damage mitigation. 19 Bird damage to fruit crops amounts to tens of millions of dollars in losses annually. Yet, 20 the development of successful damage-mitigation strategies for fruits is hindered by a lack of 21 species-specific damage information. In chapter 2, I used bioenergetic modeling that integrated 22 species-specific data on energetic demands and diet to estimate sweet cherry (Prunus avium) 23 consumption by American robins (Turdus migratorius) and cedar waxwings (Bombycilla 24 cedrorum). I then developed economic models to quantify species-specific financial loss due to 25 bird damage. Individual waxwings consumed significantly more sweet cherry and caused seven 26 times the financial loss than robins. I estimated economic losses at $US1.8 million and 27 $US147,000 from the waxwing and robin populations, respectively. 28 Species-specific variation in diet preferences could result in varying use of orchards and 29 impacts on the fruit-producing industry by different bird species. However, species-specific 30 studies of avian orchard use are lacking, particularly throughout the fruit-growing season. 31 Cultivated sweet cherries are high in sugar and low in proteins and lipids; American robins 32 typically prefer lipid-rich fruits, while cedar waxwings choose sugary fruits. Differences in diet 33 preferences may translate into species-specific patterns of habitat use for birds in fruit crops. In 34 chapter three, I used radio telemetry to quantify frequency of daily bird visits to orchards and the 35 amount of time birds spent visiting orchards each day over the fruit-ripening season. I found that 36 waxwings visited orchards a greater percentage of days than robins and spent more time in 37 orchards each day. 38 Birds forage in habitats where food abundance varies at multiple spatial scales; relative 39 resource abundance between hierarchical spatial scales likely influences within-patch foraging. 40 For frugivorous birds, fruit-growing agricultural regions provide a system of readily available 41 food resources heterogeneously distributed at increasingly broad hierarchical scales. In chapter 42 four, I conducted foraging observations and quantified fruit abundance at three spatial scales to 43 evaluate influences of fruit abundance at multiple spatial scales, and influences of sociality, on 44 avian behavior in sweet cherry orchards. Fruit abundance across multiple scales interacted to 45 influence patch residence time and proportion time spent feeding at sweet cherry trees; these 46 patterns differed between species. In addition, fruit abundance at large spatial scales influenced 47 patch residence time in robins and proportion time feeding by waxwings more strongly for birds 48 in large foraging groups than for those in small groups"--Pages ii-iii.
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