Fecal Sac Dispersal by Prothonotary Warblers: Weatherhead's Hypothesis Re-Evaluated

Abstract

Data on removal of fecal sacs by Prothonotary Warblers (Protonotaria citrea) were used to test Weatherhead's (1984) hypothesis that birds carrying fecal sacs away from the nest will vary their departure directions more widely than will birds not carrying fecal sacs in order to prevent attraction of predators. We recorded the departure direction of adults and whether or not they carried fecal sacs, as well as the distance flown to drop a fecal sac. Fecal sacs dropped over land were not carried significantly farther than those dropped over water. Although the distribution of directions flown with fecal sacs was significantly different than that of directions flown without fecal sacs, Prothonotary Warblers did not vary their departure direction more when carrying fecal sacs than when not carrying sacs. In fact, the distribution of trips without fecal sacs was more varied than trips with fecal sacs. Our results contradict the results of Weatherhead (1984), possibly because of differences in data analysis, and do not support his hypothesis of fecal sac dispersal.