Palm Warblers; Early May Migration through Northern Illinois

A Palm Warbler "Western Population" in the grass next to the Kishwaukee River,
Espenscheid Forest Preserve, Rockford, IL; 5/1/2011.

With the return of many warblers along with the nice weather of the first week of May, Palm Warblers (Above) seemed to be one of the most abundant. I saw them anywhere their was open grassy areas - especially near water. Palms have two populations which have varying amounts of yellow on their breasts. Both populations have a reddish crown with a yellow face and dark eye-line and are relatively plain brown / gray on the wings and back. The "Eastern Population" Palms have a bright yellow throat, breast, and belly which have red racing stripes along their flanks and breast. None of my photos seemed to have these guys with completely yellow undersides, so my guess they are the "Westren Poulation" which have less yellow on their breasts and bellies, but keep the yellow throat, partial yellow eyebrow and yellow near the rump. But they lack the bright red stripes on their flanks. They sport more of a muted brown stripes. In their non-breeding plumage  (Below), they lose their red crown and all yellow except near the tail.

A Palm Warbler in its non-breeding plumage, Black Hawk Springs Forest Preserve, Rockford, IL; 10/3/2010.

A Palm Warbler ("Eastern or Western Population"?), Rock Cut State Park, Rockford, IL; 5/8/2011.

Palm Warblers spend their summers in Central and Eastern Canada as well as Michigan's Upper Peninsula and northern Wisconsin and the Northeastern States. So when we see them in northern Illinois, they are travelling through from their winter grounds in the southeast as well as Mexico (where I saw them last December).

Another "Western Population" Palm Warbler, Espenscheid Forest Preserve, Rockford, IL; 5/1/2011.