Influence of Habitat and Season on Foraging Flock Composition in the European Starling (Sturnus vulgaris)

This study examines the relative importance of habitat and season in determining size and composition of foraging flocks of European Starlings (Sturnus vulgaris). We hypothesized that if season was the principal determinant of flock size, variation across seasons (within habitat) would be greater th...

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Bibliographic Details
Published in:Oecologia 1985-01, Vol.67 (4), p.532-539
Main Authors: Fischl, Joseph, Caccamise, Donald F.
Format: Article
Language:English
Subjects:
Animal and plant ecology
Animal, plant and microbial ecology
Animals
Autoecology
Biological and medical sciences
Breeding seasons
Feedlots
Flocks
Foraging
Fundamental and applied biological sciences. Psychology
Habitat preferences
Seasonal migration
Starlings
Sturnus vulgaris
Urban habitats
Vertebrata
Wildlife habitats
Winter
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Summary:This study examines the relative importance of habitat and season in determining size and composition of foraging flocks of European Starlings (Sturnus vulgaris). We hypothesized that if season was the principal determinant of flock size, variation across seasons (within habitat) would be greater than variation across habitats (within season). The calendar year was divided into 6 seasons corresponding to major stages in the annual cycle of starlings. After measuring the availibility of 15 foraging habitats occurring within the study area, we drove a 184 km route weekly (over a 17 month period) to census starling flock size, species composition, habitat use, and activity. Although flock size was influenced by both season and habitat, it varied relatively less within seasons (across habitats). Only five of nine seasons showed significant habitat effects, and two (of the five) were significant mainly because of large aggregations in habitats with unusually abundant food (e.g. feedlots, cornfields). In contrast, eight of nine habitats showed significant seasonal effects. The only exception (hay) was little used (< 1% of all birds observed). For starlings the activities associated with seasonal events of the annual cycle were a major influence on patterns of social foraging. Habitat factors were less important because of constraints imposed by seasonal factors, but under some conditions (e.g. drought, clumped food supply) they became dominant.
ISSN:0029-8549
1432-1939
DOI:10.1007/BF00790025