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SOURCE AND SINK HABITATS OF RED‐WINGED BLACKBIRDS IN A RURAL/SUBURBAN LANDSCAPE
Author(s) -
Vierling Kerri T.
Publication year - 2000
Publication title -
ecological applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.864
H-Index - 213
eISSN - 1939-5582
pISSN - 1051-0761
DOI - 10.1890/1051-0761(2000)010[1211:sashor]2.0.co;2
Subject(s) - habitat , ecology , predation , sink (geography) , wetland , population , geography , fledge , ecological trap , biology , cartography , demography , sociology
The objectives of this study were to distinguish demographic source and sink habitats of Red‐winged Blackbirds ( Agelaius phoeniceus ) and to determine the factors influencing source–sink status prior to fledging. In Boulder County, Colorado, I monitored 591 nests between 1995 and 1997 in breeding habitats that were either natural (wetlands, tallgrass prairie) or anthropogenic (hayfields, roadside ditches). To determine source–sink status, I calculated the productivity necessary to offset mortality. Predation was the main determinant of source–sink status, while brood parasitism had virtually no impact on this population. Anthropogenic habitats consistently functioned as sinks throughout the three‐year study. Sources occurred only in natural habitats, and source sites had fewer buildings nearby than did sinks. In addition, climate variability may have influenced reproduction by influencing egg‐laying dates. In 1995, possible source habitats included tallgrass prairie and wetlands. In 1996, tallgrass prairie functioned as a strong source, but in 1997 none of the natural habitats functioned as sources. The Boulder suburban area appeared to function as a regional sink during this study, possibly because human activity attracts high densities of human‐commensal predators such as raccoons and corvids that depredate Red‐winged Blackbird nests.