A Yellow Palm Warbler specimen in Illinois
Nearly 500 window-killed Palm Warbler (Setophaga palmarum) specimens reside in the Field Museum's bird collection, spanning across more than 30 years. Among these, there is only one example of the bright yellow eastern form that is often referred to by birders as Yellow Palm Warbler (Setophaga palmarum hypochrysea). It was found at McCormick Place, in Chicago's Near South Side, on 8 November 1994. This was the first fully documented record of this subspecies in Illinois. In these photos, it's the middle bird, with a typical Western Palm Warbler below (also from McCormick Place) and typical Yellow Palm Warbler (from Connecticut) above. Note the overall brighter yellow underparts that is typical of Yellow Palm Warbler, compared to the drabber underparts of Western Palm Warbler. The detailed specimen information is below the photos.
Specimen info, from top to bottom
FMNH 150545; Setophaga palmarum hypochrysea (Yellow Palm Warbler); 16 October 1901; New Haven, Connecticut
FMNH 367228; Setophaga palmarum hypochrysea (Yellow Palm Warbler); 8 November 1994; Chicago, Illinois
FMNH 380774; Setophaga palmarum palmarum (Western Palm Warbler); 14 October 1995; Chicago, Illinois