Search behavior of arboreal insectivorous migrants at Gulf Coast stopover sites in spring

Search behavior of arboreal insectivorous migrants was studied at three stopover sites along the northern coast of the Gulf of Mexico during spring migrations, 1993-1995. We examined if search behavior was affected by phylogeny, or by environmental factors. A sequence of search movements (hop, flutter, or flight) in a foraging bout was recorded for each migrant encountered. Search rate, frequency, and distance of movements were calculated for each species. Search rate was positively correlated with proportion of hop, but negatively correlated to flight distance. Hop distance was positively correlated to tarsus length, as was flight distance to wing length for the 31 species of migrants. Cluster analysis indicated closely related species generally have similar foraging modes, which range from 'sit-and-wait' of flycatchers to 'widely foraging' of warblers. Migrants tended to use more hops in dense vegetation, but more flights in areas with sparse vegetation. Migrants also used more flights when foraging in mixed-species flocks and during periods of high migrant density. Logistic models indicated warblers were more influenced by environmental factors than vireos, possibly because warblers are near-perch searchers and more affected by these factors. Received 6 May 2010. Accepted 17 December 2010.
Numerous studies have reported on the search behavior of forest birds (Williamson 1971; Morton 1980; Fitzpatrick 1981; Robinson and Holmes 1982, 1984; Holmes and Recher 1986; Hutto 1988; Lovette and [...]