thumbnail

Conservation of the yellow-shouldered blackbird, Agelaius xanthomus, an endangered West Indian species

Biological Conservation

doi:10.1016/0006-3207(91)90052-B
By:
, , and

Links

Abstract

The yellow-shouldered blackbird Agelaius xanthomus, endemic to Puerto Rico and Mona Island, is endangered, mainly because of brood parasitism by the shiny cowbird Molothrus bonariensis, which reached Puerto Rico at least 30 years ago. The yellow-shouldered blackbird populations have since declined, about 770?1200 remaining (470?900 on Mona Island) by 1982?1986 compared to a population of about 2400 in 1975. Nearly all nests of blackbirds in most of its habitats are parasitized by cowbirds. This significantly reduces nesting success, but blackbirds have evolved no defenses against brood parasitism. Removal of cowbirds from the yellow-shouldered blackbird nesting grounds, modeled after similar programmes for the brown-headed cowbird Molothrus ater on Kirtland's warbler Dendroica kirtlandii nesting areas, significantly increased blackbird production. Blackbirds readily accept nest boxes, and breeding populations can be established in otherwise unusable sites and can be concentrated in mangrove habitats, were they are more easily protected by cowbird removal. Furthermore, yellow-shouldered blackbird pairs using cavities, including nest boxes, fledged more young per nest than pairs using open nests.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Conservation of the yellow-shouldered blackbird, Agelaius xanthomus, an endangered West Indian species
Series title:
Biological Conservation
Volume
55
Issue:
2
Year Published:
1991
Language:
English
Publisher:
U.S. Fish and Wildlife Service
Contributing office(s):
Patuxent Wildlife Research Center
Description:
119-138
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Biological Conservation
First page:
119
Last page:
138