Winter foraging behavior by Eastern phoebes (Sayornis phoebe) in central Texas




Troy, Jeffrey R.

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I investigated potential effects of weather and habitat conditions on foraging effort, foraging rate, aerial hawking percentage, height of sally initiation and sally distance in Eastern Phoebes during the winter of 2004-2005. I also examined perch return frequency as a function of vegetative (perch) availability and sally distance, and tested the hypothesis that average “give-up” distances were > 2 times that of average sally distances. I found effort per foraging movement decreased with increasing ambient temperature in birds that foraged > 50 m from water sources, but not in birds that foraged < 25 m from water. Foraging rate increased with progression of calendar date. Aerial hawking percentage increased as ambient temperature increased. Average height of sally initiation was not significantly affected by weather or habitat conditions. Average sally distance did not vary with ambient temperature or height of sally initiation, but did tend to increase in increasingly open habitats. Perch return frequency tended to decrease with increased vegetative availability, but was unaffected by average sally distance. These results suggest that temperature and habitat conditions affected some foraging behaviors in Eastern Phoebes. Average “give-up” distances were greater than twice that of average sally distances, presumably giving birds new fields of view from new perches. Other observed behaviors of interest include 5 individuals that foraged through aerial insect swarms and appeared to capture more than 1 prey item during single aerial foraging events, as well as aggressive behaviors that could be viewed as indirect evidence of winter territoriality.



eastern phoebe, predation


Troy, J. R. (2005). Winter foraging behavior by Eastern phoebes (Sayornis phoebe) in central Texas (Unpublished thesis). Texas State University-San Marcos, San Marcos, Texas.


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