Understanding Declines in Rusty Blackbirds

Russell Greenberg, Dean W. Demarest, Steven M. Matsuoka, Claudia Mettke-Hofmann, David Evers, Paul B. Hamel, Jason Luscier, Luke L. Powell, David Shaw, Michael L. Avery, Keith A. Hobson, Peter J. Blancher, Daniel K. Niven

Research output: Chapter in Book/Report/Conference proceedingChapter

Abstract

The Rusty Blackbird (Euphagus carolinus), a formerly common breeding species of boreal wetlands, has exhibited the most marked decline of any North American landbird. North American Breeding Bird Survey (BBS) trends in abundance are estimated to be -12.5yr over the last 40 years, which is tantamount to a textgreater95% cumulative decline. Trends in abundance calculated from Christmas Bird Counts (CBC) for a similar period indicate a range-wide decline of -5.6yr. Qualitative analyses of ornithological accounts suggest the species has been declining for over a century. Several studies document range retraction in the southern boreal forest, whereas limited data suggest that abundance may be more stable in more northerly areas. The major hypotheses for the decline include degradation of boreal habitats from logging and agricultural development, mercury contamination, and wetland desiccation resulting from global warming. Other likely reasons for decline include loss or degradation of wooded wetlands of the southeastern U. S and mortality associated with abatement efforts targeting nuisance blackbirds. In addition, the patchy breeding distribution of this species may inhibit population consolidation, causing local populations to crash when reduced to low levels. Progress in understanding the causes and mechanisms for observed declines has remained limited until recently. Here we present initial attempts to understand the habitat requirements of Rusty Blackbirds and offer specific predictions associated with each of the hypotheses for decline as a way of guiding future research.
Original languageEnglish (US)
Title of host publicationBoreal Birds of North America
Subtitle of host publicationA Hemispheric View of Their Conservation Links and Significance
EditorsJ. V. Wells
Place of PublicationBerkeley, CA
PublisherUniversity of California Press
Pages107-125
Number of pages19
Volume41
ISBN (Print)978-0-520-95058-0
StatePublished - 2011

Publication series

NameStudies in Avian Biology
PublisherUniversity of California Press

Keywords

  • INHS

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