Gambel's White-crowned Sparrow, Fernhill Wetlands, Forest Grove, Oregon on 16 April 2010 by Greg Gillson. Notice bright white head stripes, pale stripes on back, orange bill, clean gray underparts.
White-crowned Sparrows are moving through the Pacific Northwest right now. I photographed this bird recently in NW Oregon.
As discussed last year (In the backyard... White-crowned Sparrow), there are 5 populations across North America.
West of the Cascades, from SW British Columbia to NW California, these represent two populations. The Puget Sound White-crowned Sparrow nests in this area and is now moving into breeding habitats--coastal headlands, valley pastures, and western Cascade clear-cuts.
On a broad band across the west, the Gambel's White-crowned Sparrow is also migrating north now. It will breed in interior British Columbia, western Alberta, and Alaska.
These birds sing during migration. The songs of the various populations across North America are different. Indeed, songs can be slightly different even within populations, as young birds learn to sing whatever local dialect they hear.
Puget Sound White-crowned Sparrow, Hayward, Oregon on 16 May 2008 by Greg Gillson. Notice dingy white head stripes, dull two-tone brown back, yellow bill, brownish sides.
If you want to practice separating songs, now is the time.
I transcribe the "typical" song of Puget Sound White-crowned Sparrow as a lively and sweet:
wee SWEE chilly-chilly-SWEEE cheer-cher-er
On the other hand, the song of the Gambel's White-crowned Sparrow is more mournful, with downward-sliding emphasized notes:
WEE chur chilly-chilly-CHUR
The White-crownd Sparrow songs on the Cornell Lab's online field guide are not exactly the songs I usually hear in NW Oregon, but close enough.
The song marked as "Alaska August 2006 by Geritt Vyn" is a Gambel's.
The song marked as "Oregon June 1988 Geoffery A. Keller" is a Puget Sound.
A note on field guides.
Sibley has a "Pacific" form that includes Puget Sound White-crown and the non-migratory Nuttall's form of the central California coast. The "Interior West" is the Mountain White-crown. "West Taiga" is Gambel's. "East Taiga" is the nominate leucophrys subspecies.
The National Geographic guide shows the dark-lored, pink-billed as leucophrys (includes Mountain White-crown). The pale-lored birds are split between the bright Gambel's with orange bill and the duller and browner Nuttall's with yellow bill (includes Puget Sound White-crown).
Confused? I hope not. But you can practice again in September when the birds migrate south.... Or, eastward from the Cascades practice looking for the dark-lored Mountain White-crowned among the more abundant Gambel's....