Food Size And Foraging Site Selection In A Breeding Population Of Red- Winged Blackbirds (Agelaius Phoeniceus)

Date of Graduation

Spring 1975


Master of Science in Biology



Committee Chair

Tom Stombough


The size of organisms fed to nestling red-winged blackbirds was significantly larger than if selection of food were random. There also appeared to be a selection for "soft-bodied" items. This may be due to selection for soft anatomy per se or selection as a function of the ease of capture. The average size of organisms captured in the marsh was significantly larger than those in the adjacent field. This indicated that in terms of feeding efficiency, the field is a less profitable place to forage than the marsh. Female adult red-winged blackbirds were found to feed significantly less often on the field than males. This reduces intraspecific competition and may increase feeding efficiency. It was postulated that there exist two levels of selection during nestling feeding: a selection for larger food items and for foraging sites. As female red-winged blackbirds feed the nestlings unassisted by males, it is necessary for the females to maximize feeding efficiency by selecting the largest items compatible with the energy expense of capture and by selecting foraging locations where these larger items can be found.

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© Stephen Wallace Wilson