DigitalCommons@University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Prey Selection by Birds of Prey Prey Selection by Birds of Prey

Prey selection is key to determine predator prey interaction and understanding the complexity of food web structure. In this thesis, we used two different approaches to understanding prey selection by North American birds of prey. Using a conventional method, in Chapter 1 we compared pellet analysis and trapping data to assess patterns of prey selection of barn owls in western Nebraska. Microtus spp. comprised 55.8% of the prey items in the barn owl’s diet. The proportion of several prey types in the diet were significantly different from the expected proportion based on trapping. This pattern may indicate barn owls actively select Microtus spp. , possibly because they are a relatively more energetically rewarding prey. In Chapter 2, we quantified the prey selection of migrating Sharp-shinned hawks and Cooper’s hawks using DNA barcoding. Red-winged blackbirds ( Agelaius phoeniceus ) and rock pigeons ( Columba livia ) were the most common prey of Cooper’s hawk, and American robins ( Turdus migratorius) were the most common prey of sharp-shinned hawks. Our results indicate that these raptors tend to consume relatively common prey species, possibly reflecting an energy conserving migration strategy. Detailed understanding of raptor diet is essential to identify their potential vulnerabilities and to develop effective conservation strategies. ABSTRACT Research on prey selection strategies are important for understanding the connections between predators and their prey communities. Studies on prey selection by barn owls show contradictory results; some showed that they are efficient samplers of the small mammal communities whereas others claimed that they take prey disproportionately indicating they have preference. Here we compared pellet analysis and trapping data to assess patterns of prey selection of barn owls in western Nebraska. Microtus species. comprised 55.8% of the 1,163 prey items. The proportion of several prey types in the diet was significantly different from the expected proportion based on trapping. Microtus occurred more frequently in the diet whereas Peromyscus occurred less frequently in diet than expected. This pattern may indicate barn owls actively select Microtus spp. , possibly because are twice as large as Peromyscus and are therefore relatively more energetically rewarding prey. Alternatively, it suggests that Microtus may be more available to barn owls than Peromyscus . ABSTRACT Almost 66% of raptors migrate every year, however there is limited information on prey selection by migrating raptors. This is due in part to the logistical challenges of observing prey capture or hunting while raptors are en route . In this study, we quantified the prey selection of migrating Sharp-shinned hawks (Accipiter striatus ) and Cooper’s hawks ( Accipiter Cooperii ) using DNA barcoding. We compared 16S mitochondrial gene sequences of prey feathers or remains from the talons or beaks of hawks captured at Cape May, New Jersey, to reference samples at GenBank to identify prey. Red-winged blackbirds ( Agelaius phoeniceus ) and rock pigeons ( Columba livia ) were the most common prey of Cooper’s hawk, and American robins ( Turdus migratorius) were the most common prey of Sharp-shinned hawks. Our results indicate that these hawks select common and abundant prey species during migration, possibly reflecting an opportunistic, energy conserving migration strategy.