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Thanks for participating! Here is the answer:
The fact that this bird is poking it's head out of a cavity makes me immediately think of a woodpecker. The red throat patch, large white supercilium (line above eye) and white malar stripe (line through "cheek") on a mostly black head points to only one bird: a male Williamson's Sapsucker. One more hint is that this bird is nesting in a Quaking Aspen... they love Aspen!
I took this photo of a male Williamson's Sapsucker in June 2008 in the Rio Grande National Forest.
Here are the people who submitted correct answers:
Karen Carlsen
Laurie Foss
Sajni Kallichanda
Joel Such
Marcel Such
Deirdre Viel
Eric Wood