The influence of weather, geography, and habitat on migrating raptors on Cape May Peninsula

Lawrence J. Niles, Joanna Burger, Kathleen E. Clark

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


For many shorebirds and passerines, stopovers in areas of concentrated resources increase survival during migration. For raptors, physical factors have generally been considered to be the chief influence on migratory behavior, and few studies have collected quantitative data on the use of resting and foraging habitat during migration. Our object was to survey three different habitats along a 30-km section of the Cape May peninsula. We measured abundance, flight altitude, and flight direction of eight species of migrating raptors to evaluate the influence of habitat and physical factors, including wind speed, wind direction, and location, on migratory behavior. Physical factors such as wind speed and direction were weakly related to bird density and altitude. Although interactions among physical factors were significant, they were not consistent with predictions based on bird mass or wing-aspect ratio. Habitat type was significantly associated with most species' altitude and density. Birds generally occurred in higher densities and at lower altitudes above habitats similar to those used in breeding or wintering seasons. We suggest that the strong habitat association is due to the need for suitable foraging sites. Many migratory raptors are able to prey upon migratory birds, insects, and fish that also concentrate at the end of the Cape May peninsula or in waters offshore. Most of the raptors observed in Cape May are immature and inexperienced, and the concentration of similarly immature and inexperienced prey may prove to be a critical factor in successful migration along the Atlantic Coast.

Original languageEnglish (US)
Pages (from-to)382-394
Number of pages13
Issue number2
StatePublished - May 1996

All Science Journal Classification (ASJC) codes

  • Ecology, Evolution, Behavior and Systematics
  • Animal Science and Zoology


  • Cape May
  • Migration
  • habitat
  • prey
  • raptors
  • stopover


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