Friday, September 17, 2010

Black-throated Blue Warbler

Thursday evening I banded a male Black-throated Blue Warbler (see photo above).  The female in the lower photo is a previous year's bird.  This bird is one of the few warblers that does not molt into a CFW (confusing fall warbler) plumage--males remain bright throughout the year. The sexes look so different that mid-19th century ornithologists thought males and females were different species. 

Black-throated Blue Warblers breed in dense boreal forests in northeast North America and down the Appalachians. The species nests only as far west as the Arrowhead of Minnesota.  Logging and clearing have probably caused population declines during the last 300 years.  As many fields and pastures return to forest, populations of this warbler are increasing.   In the future, populations again may fall due to deforestation in the Caribbean, where Black-throated Blue Warblers spend the winter (Holmes et al. 2005).

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