Differential autumn migration of Sharp-shinned and Cooper's Hawks in western North America

Article Abstract:

Sharp-shinned and Cooper's Hawks exhibit differential migration timing during fall in New Mexico and Nevada, but the order in which they migrate differs from some noted theories of differential migration, such as body size and social dominance. A new study shows a sex-specific differential migration timing in the two species, the order being: juvenile females, juvenile males, adult females and adult males, It is suggested that the age-related differences may be explained by foraging efficiency and that rate of travel may explain sex-related differences.

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Wintering Swainson's Hawks in California's Sacramento-San Joaquin river delta

Article Abstract:

Swainson's Hawks regularly winter in the Sacramento-San Joaquin River Delta. They breed mainly in the Central Valley and on the Northeastern Plateau in California. The presence of ample foraging opportunities due to corn and wheat farming results in the failure of migration. Foraging groups are formed by breeding birds which spent their foraging time in hunting. Foraging is prevented by dense fog.

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Using hydrogen isotope geochemistry to estimate the natal latitudes of immature Cooper's hawks migrating through the Florida Keys

Article Abstract:

Research is presented concerning the natal origin of immature Cooper's hawks which were captured during their migration through the Florida Keys. The majority were found to originate in the Southeast and Mid-Atlantic regions.

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