Sunday, May 6, 2012

Palm Warbler

Although Palm Warblers are common migrants in our part of Minnesota, my only decent photograph was of the winter-plumaged bird in the first photo. I encountered that individual in downtown Key West in February 2011. (Palm Warblers were first found in Hispaniola, which accounts for their name.) Actually Palm Warblers breed in bogs and fens and enjoy one of the more northern breeding ranges of all warblers. Spring-plumaged birds are a whole lot brighter than those in winter plumage, as you can see in the next photographs. I banded this bird, my first for Minnesota, in Northfield on Friday. (I banded a few Palm Warblers in South Dakota, but never photographed one.)
Palm Warblers are recognized by their chestnut caps, yellow throats and under-tail coverts, and habitual tail bobbing. Two races are recognized and are fairly easily identifiable in the field. The Yellow Palm Warbler of eastern Canada and New England has completely yellow underparts. The Western Palm Warbler, which breeds west of Ottawa and uncommonly in Minnesota's Arrowhead, lack yellow across their mid-breasts.
The Western Palm Warbler is the race expected during migration in Minnesota and, as you can easily tell in my photographs, that is exactly what I banded in Northfield. Apparently the two races interbreed where their ranges meet. Wilson (1996) warns, however, that evidence for this intrebreeding is based on very few specimens and that "studies on the interactions of the two subspecies are needed."

Identifying the races of Palm Warblers may be more difficult than some books suggest. Chris Wood, of the Cornell Laboratory of Ornithology, writes "There is alarge amount of variation in both Western and Yellow Palm Warblers and the extent of yellow on the underparts is particularly variable in spring. A fair number of Western Palm Warblers are [extensively] yellow below. I would look more at the color of the nape and wings, which would be more strongly olive in Yellow Palm Warbler. The back of the auricular should be more yellowish, or at the very least a bit more olive. Yellow Palms also should show... extensive chestnut streaking on the sides of the breast ..."

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