Spring migration patterns of male red-winged blackbirds (Agelaius phoeniceus) from two migratory roosts in South Dakota and Minnesota
Knittle, C.E.; Linz, G., M.; Cummings, J., L.; Davis, J., E.,. Jr.;; Johns, B., E.; Besser, J., F.
American Midland Naturalist 136(1): 134-142
ISSN/ISBN: 0003-0031 DOI: 10.2307/2426638
During March 1985 male red-winged blackbirds (Agelaius phoeniceus) were marked with aerially applied fluorescent colored pigments at two migratory roost sites in southeastern South Dakota and western Minnesota to determine their dispersal to breeding areas. Postspray samples revealed that approximately 54% (1.58 million) of the males present were marked with at least one of four pigments used. During late spring breeding males were shot in 16 predetermined collecting areas in four N-central states in the United States and three central Canadian provinces. Of 3289 males collected 555 (16.9%) were marked with one or more pigments; 86.8% (482) of the marked birds were from the South Dakota marking site and 13.2% (73) from the Minnesota site. The 16 collecting areas where male redwings were shot were grouped into six recovery regions for chi-square analysis. Results showed unequal proportions of marked breeding males among the recovery areas (P = <0.001). Temporal use of the South Dakota roost site by migrating males also affected breeding male distribution (P = <0.001). Inadequate sample sizes precluded analysis of temporal distribution of marked birds from the Minnesota marking site. Although marked redwings were dispersed over several thousand square kilometers from South Dakota to Alberta, Canada, 76% of the marked male redwings from South Dakota were concentrated in southern Saskatchewan and N-central North Dakota; 74% of the marked birds from Minnesota were concentrated more easterly in southern Manitoba, northeastern North Dakota and northwestern Minnesota. The N-northwestward distances traveled by migrating male redwings from marking sites to breeding areas was significantly different (P = 0.006) among groups marked at different time intervals at each site. Distances traveled ranged from 856 km to 1093 km. Reprinted by permission of the publisher.