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There are few published data on annual survival and no reports of lifetime reproduction for breeding Cooper's Hawks (Accipiter cooperii). Breeding males (n = 105) in central and southeastern Wisconsin had an annual mortality rate of 19%. or a survival rate of 81% for birds ≤ 10 years of age. We did not detect significant differences in mortality rates between urban and rural habitats, nor between the earlier 13 years and later 13 years of this study. Male Cooper's Hawks produced from zero to 32 nestlings during their lifetimes. Body mass or size appeared unrelated to annual survivorship and lifetime reproduction, although lifetime reproduction was correlated strongly with longevity of breeding males. Fifteen of 66 males (23%) produced most (53%) of the nestlings. Our studies occurred in an area where breeding populations may be increasing with some of the highest reported productivity indices and nesting densities for this species. Habitat used for nesting on our Wisconsin study areas may be less important for survivorship and lifetime reproduction than acquisition of a nesting area in which a male will breed throughout his life. [ABSTRACT FROM AUTHOR]

We investigated several reproductive attributes among three spatially and morphometrically separable northern populations of breeding Cooper's Hawks (Accipiter cooperii) in differing ecological settings in British Columbia, North Dakota, and Wisconsin during 1995-2001. We did not detect significant inter-year variation in reproduction within any of our study areas. Cumulative clutch and brood sizes were significantly higher in British Columbia (mean = 4.41 and 3,60, respectively) and Wisconsin (4.26 and 3.73) than in North Dakota (3.5 and 3.0), but not significantly different between British Columbia and Wisconsin. Total nest success rates (91 and 82% in British Columbia and Wisconsin, respectively) varied significantly among all three study sites, but were lowest in North Dakota (68%). We hypothesize that smaller clutch and consequentially lower brood sizes in North Dakota may be the result of the comparatively later nesting phenology in this highly migratory population. Our results underscore the significance of clutch size data, and the need for further research on regional and other large-scale variation in avian demographic parameters to help decide if, when, and where population demographics may warrant a management response. [ABSTRACT FROM AUTHOR]

Urban landscapes vary greatly across North America and long-term data on the nesting biology of Cooper's hawks (Accipiter cooperii) from a variety of urban environments will improve our understanding of these poorly studied populations. We studied Cooper's hawks nesting in the metropolitan Milwaukee area, Wisconsin, USA, over a 12-year period, 1993-2004. Nesting success for 254 first nesting attempts averaged 64.6% with means of 2.27 young per laying pair and 3.53 young per successful pair. For 8 second nesting attempts (i.e., re-nests), nesting success averaged 87.5% with means of 2.57 young per laying pair and 3.00 young per successful pair. Productivity for first nesting attempts did not vary over the 12-year period, and productivity for re-nests did not differ from first nesting attempts. We documented evidence of nest predation by raccoons (Procyon lotor) and red-tailed hawks (Buteo jamaicensis). On average, second year (SY [i.e., 1-yr-old]) Cooper's hawks comprised 14.6% (43 of 295 breeding birds; 21.5% [37 of 172] of F and 4.9% [6 of 123] of M) of the known breeding population. The percentage of SY breeders within this population declined over the 12-year period, suggesting a relatively young population. Cooper's hawks consistently reoccupied nest sites annually after initial discovery over an estimated 2 generations of breeding adults, suggesting that population density for our study was at least stable. We trapped 105 breeding adults, including 5 natal dispersal birds. Based on long-term, relatively high reproduction, repeated re-occupancy of nest sites, and confirmed recruitment from within this population, we suggest that these nesting areas were not marginal or inferior habitats and that urban Cooper's hawks in this study area were not a sink population. We recommend no active management of this population at this time; however, additional information for nesting Cooper's hawks from other urban environs will expand our knowledge base for these populations. [ABSTRACT FROM AUTHOR]

Studies the nesting ecology of Cooper's Hawks in Wisconsin. Assessment of quality of nesting areas; Determination of hatching dates by backdating; Investigation of the possibility of nonrandom mating; Analysis of adult mass; Results and discussion.