Combining migration and wintering counts to enhance understanding of population change in a generalist raptor species, the North American Red-tailed Hawk

Neil Paprocki, Dave Oleyar, David Brandes, Laurie Goodrich, Tara Crewe, Stephen W. Hoffman

Research output: Contribution to journalArticle

Abstract

An increasing body of scientific evidence supports the idea that many avian species are changing their migratory behavior as a result of climate change, land-use change, or both. We assessed Red-tailed Hawk (Buteo jamaicensis) population trends in 2 parts of the annual cycle (fall migration and winter) to better understand regional population trends and their relationship to changes in migration. We conducted 10 yr, 20 yr, and 30 yr trend analyses using pan-North American standardized fall migration counts and Christmas Bird Counts. We quantitatively compared trends in seasonal counts by latitude within the eastern and western migratory flyways. Our combined analysis of migration and wintering count data revealed flyway-specific patterns in count trends suggesting that Red-tailed Hawks are undergoing substantial changes in both migratory behavior and population size. Decreasing Red-tailed Hawk wintering and migration counts in southern regions and increasing winter counts in northern regions were consistent with other observations indicating changes in migratory strategy; an increasing number of Red-tailed Hawks do not migrate, or migrate shorter distances than they did in the past. Further, Red-tailed Hawk populations have been stable or increasing across much of North America. However, we found strong negative count trends at the northernmost migration sites on the eastern flyway, suggesting possible breeding-population declines in the central and eastern Canadian provinces. Our findings demonstrate the benefit of using appropriate data from multiple seasons of the annual cycle to provide insight into shifting avian migration strategies and population change.

Original languageEnglish
Pages (from-to)98-107
Number of pages10
JournalCondor
Volume119
Issue number1
DOIs
Publication statusPublished - 8 Feb 2017
Externally publishedYes

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