Aaron N K Haiman Cooper s Hawk Diet 8 May 2006 Prey Selection of Cooper s Hawks Accipiter cooperii Nesting in Urban Areas of Berkeley and Albany California Aaron N K Haiman Abstract The Cooper s Hawk is one of the few species of top predators that can persist in urban areas Little is known however on the dynamics between urbanization and the species that adapt and persist in these areas One requirement for the survival of Cooper s Hawks in urban areas is prey availability To determine the prey species of the Cooper s Hawk in the urban areas of Berkeley and Albany California I analyzed the previously identified 579 prey remains of the 2002 breeding season To this dataset I added the 478 prey remains collected from Cooper s Hawk nest sites during the 2003 breeding season which had not been identified In 2002 16 species of bird and 3 species of mammal were found In 2003 20 species of bird and 1 species of mammal were found Of these species Rock Dove Mourning Dove and American Robin comprised 80 of the biomass of their diet The percentage of non native biomass of the diet was higher on average in more urban nests 65 than in park nests 25 Most of this biomass was brought to the nest in the mid section of the breeding season Determining how the Cooper s Hawk is able to survive and reproduce in such close proximity to human activity and disturbance can lead to better management decisions with respect to this species and others in the future p 1 Aaron N K Haiman Cooper s Hawk Diet 8 May 2006 Introduction The amount of land covered by urban development and the effects of urbanization on species distribution are increasing throughout the world every year Vitousek et al 1997 One way that urbanization changes the natural environment quickly and disruptively is by the displacement of species Beissinger and Osborne 1982 Mills 1989 Bell et al 1995 Estes and Mannan 2003 Urban habitats are usually very different from preexisting habitats in terms of changes in temperature gradients precipitation levels runoff patterns and amount and quality of topsoil Herrick 1995 Many species of wildlife such as the Bachman s Sparrow Aimophila aestivalis and the Striped Shiner Luxilus chrysocephalus cannot tolerate urban environments and are subsequently displaced Schweizer and Matlack 2005 Dunning and Watts 1990 Some species however can cope with such disturbances and will persist in urban environments These include the Cooper s Hawk Accipiter cooperii the focus of this study and the Eastern Fox Squirrel Sciurus niger Salsbury et al 2004 Barry et al 1998 A cooperii Bonaparte is a medium sized raptor that occurs throughout southern Canada the continental United States and Mexico Ferguson Lees 2001 As a top predator it feeds on a wide variety of small to medium sized songbirds game birds and small to medium sized rodents and reptiles Wheeler 2003 Roth and Lima 2003 It breeds in mature trees and nesting can begin as early as February and chicks can still be receiving food from the adults until October A cooperii has a high tolerance for urbanized environments and has been a successfully breeding bird in numerous urban areas throughout the U S including Tucson Arizona Estes and Mannan 2003 Stevens Point Wisconsin Rosenfield 1996 and Berkeley California Pericoli and Fish 2004 For the purpose of this paper success is defined as the fledging of at least one young at a given nest site in a given year Pericoli and Fish 2004 The survival of top predators in urban environments depends upon these predators finding suitable habitat large enough territories and other resources one of which is food The prey species of Cooper s Hawks that live in urban environments will necessarily be tolerant of human impacts Since all species cannot survive in urban landscapes the number of species that are available to A cooperii as prey in such landscapes will be more limited than in rural habitats with lower levels of human disturbance Peeters and Peeters 2005 It has been shown that more omnivorous species are better adapted to survive in urban environments than more specialized species Clergeau et al 1998 However a result of reduced prey diversity can be prey specialization whereby a predator becomes very successful at capturing a limited number of prey p 2 Aaron N K Haiman Cooper s Hawk Diet 8 May 2006 species but loses behaviors required for capturing a broader prey base Kauffman et al 2004 Such specialization can benefit a predator but it can also expose the predator to stressors if one or more of the prey species on which it specializes becomes scarce Prey specialization can result from anthropogenic effects or by natural processes Regardless of how specialization develops the results can be the same One of the results that can negatively affect a predator is if the prey acts as a vector for disease Doves throughout the United States can carry trichomoniasis a disease that can prove fatal to Cooper s Hawks Stabler 1954 These doves can pass the disease on to young Cooper s Hawks when the infected flesh is eaten Estes and Mannan 2003 If the Cooper s Hawks depend too strongly on doves for food they may be exposed to this disease at a higher rate than rural populations The rates of infection vary across the Cooper s Hawk range and it has been found that the infection rates in urban environments are higher than the infection rates in nearby rural environments Rosenfield et al 2002 As we come to better understand what the effects of urbanization on ecosystems are we will better understand how and when to buffer habitats and species from the more harmful of those effects Mills 1989 By identifying the characteristics of a successful habitat of a target species the specific conservation needs of that species can be better understood More informed management decisions can then be made to plan further urban development so that the aspects of a habitat that are required for a species are left unharmed and so preserve biodiversity In this way we can avoid degraded habitats and ecological traps habitats that can support a population temporarily but not indefinitely Battin 2004 Without such understanding habitats will be destroyed and species that might have been saved may become extinct Castelletta et al 2000 Jones 2003 Further managing urban development so that top predators are conserved will necessarily mean developing in a way that will conserve the species and aspects of habitat on which the top predator depends In this manner the
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