Feeding Habitats of Spring-Migrating Blackbirds in East-central South Dakota

Authors

Richard S. Sawin, North Dakota State University-Fargo
George M. Linz, United States Department of Agriculture, Great Plains Field Station, Bismarck, North DakotaFollow
William J. Bleier, North Dakota State UniversityFollow
H. Jeffrey Homan, United States Department of Agriculture, National Wildlife Research Center, Great Plains Field Station, Bismarck, North DakotaFollow

Date of this Version

6-2006

Document Type

Article

Citation

The Prairie Naturalist (June 2006) 38(2): 73-84

Associate editor for ornithology: Gregory A.. Smith

Comments

United States government work

Abstract

Between March 27 and April 21, 1998, we monitored blackbird (Icteridae) activity and habitat selection at a migratory staging area in east-central South Dakota. We used fixed-area observation points located within 20 l-km² circular plots centered on four wetland basins that were used as night roosts. Each roost was surveyed four times, with the surveys spread evenly throughout the blackbird migration. We recorded the number of blackbird flocks, flock size and composition, habitat used, and behavior (e.g., loafing and feeding). Fifty percent (n = 242) of the 482 flocks recorded in the quadrats was observed loafing in trees of woodlots and shelterbelts. Feeding flocks preferred habitats classified as Corn (e.g., disked, plowed, and stubble corn fields) over two other foraging habitat categories (Cultivated and Grassland). A comparison of proportional availability of Cultivated habitat (soybean [Lathyrus odoratus] and wheat [Triticum aestivum] stubble, inclusive) against proportional use by feeding flocks indicated that this habitat was avoided. Grassland habitat (hayfields, CRP, and pasture) was used according to its availability. Intensity of Grassland use depended on time of survey (AM and PM), with use greater during the PM survey. A two-factor model (habitat, time, and the interaction term) provided the best parsimonious fit of 15 a priori models tested with Akaike's information criterion (AIC_c). Selection of foraging habitats by blackbirds might reflect comparable strategies used by other early migrating granivores. This knowledge could help wildlife managers maximize the placement of corn field food plots for optimum benefit to wildlife species.