On 30 September Peter Scully found a non-wingbarred Phylloscopus-type warbler on Gambell, St. Lawrence Island, Alaska. It was later photographed and is thought to be either an especially dull-looking ABA Code-4 Willow Warbler (Phylloscopus trochilus) or it could be North America's first Common Chiffchaff (Phylloscopus collybita). The separation of these two difficult to identify species may require better photos to conclusively identify. A detailed comparison between Willow Warbler and Common Chiffchaff can be found in Warblers of Europe, Asian and North Africa, Baker, pp. 256-257 and Plate 26 depicts both species.
Common Chiffchaff is a common and widespread resident of the lowlands and mountains of Eurasia (east to central Siberia to the Kolyma River), wintering in the Mediterranean region and northern and northeastern Africa east to India. Chiffchaff and Willow Warbler occupy the same habitats but the former seems to be more dependent on trees. In its breeding areas, they are approachable and easy to observe. The European population alone is estimated at 16.5 million pairs. Two of the six described subspecies are altitudinal migrants, the other four being migratory (Handbook of the Birds of the World, Volume 11).
The recent photograph can be viewed at:
http://www.flickr.com/photos/scullybirds/
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