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We used the North American Breeding Bird Survey to estimate trends of red-winged blackbirds (Agelaius phoeniceus), common grackles (Quiscalus quiscula), brown-headed cowbirds (Molothrus ater), and starlings (Sturnus vulgaris) for 1966-76 in the United States and Canada. Extended to a continental scale, the survey indicated significant increases in the mean number of redwings, cowbirds, and starlings observed per route. Starlings had the greatest increase, 4.96 birds per route or a 19.4% increase. The starlings' greatest regional increases occurred in the western United States. Populations of redwings increased most in the St. Lawrence Valley and parts of the Midwest and Lower Plains regions. Cowbirds increased the most in the plains from Iowa to Saskatchewan and decreased over parts of the eastern and midwestern United States. Grackle populations indicated no change on a continental scale but did show strong increases in the Midwest and Lower Plains regions and declines in Appalachia. This knowledge of blackbird and starling population trends in specific areas should improve our ability to understand increasing bird-man conflicts, to evaluate proposed bird-damage control strategies, and to develop more effective, long-term solutions than are available at present.
A bibliography comprising annotated citations of 2037 scientific and technical publications from ten series issued by the U.S. Fish and Wildlife Service. Includes a six-page introduction containing a history of the Service and a description of the research and development series.
Report on activities in the divisions of research.
In the past two centuries, cowbirds have increased in numbers and extended their range across North America, while many of the native songbird species whose nests they parasitize to raise their young have declined. This timely book collects forty essays by most of the principal authorities on the biology and management of cowbirds. The book's goals are to explore the biology of cowbirds, the threats they pose to host species and populations, and the management programs that are being undertaken to minimize these threats. The book is organized into five sections, each with an extended editors' introduction that places the contributions in a broad, up-to-date setting. The sections cover: The changing abundance of cowbirds and the ways in which their numbers can be estimated. Host choice by cowbirds, the negative effects of cowbirds on particular host species, and the daily patterns of cowbird behavior. Behavioral interactions between cowbirds and specific host species. Patterns of cowbird abundance and host use across varying landscapes. Management programs designed to control cowbirds and protect threatened songbirds.