Rose-breasted Grosbeak - Pheucticus ludovicianus
September 20, 2011
Last Thursday I was able to clock in some time at the zoology lab. I made a study skin of another Pheucticus ludovicianus. This is the forth that I have worked on since returning to the Field to continue my volunteer work in the bird division. Two were fully mature males, one was a female, and then this one (in the photos above) was an immature fall male. Adult Rose-breasted Grosbeak males have bold color contrasts: solid black head, wings, and back contrasted with a white breast and a patch of rosy red at the neck. Adult females look more like large sparrows: brown, with lots of dark streaking. An immature male will sort of look like a hybrid between female and adult male plumage. It will be brown with lots of dark streaking except there will be some patches of that gorgeous strawberry red.
Aside from the plumage, another indication that this was not a fully mature male was that when I looked at the skull, the bone was not fully ossified. Bone ossification in passerine birds will yield a fine stippling pattern throughout the skull. This male's skull was only about 40% ossified, meaning the stippling pattern only covered roughly 40% of his skull bone.
The last I checked, grosbeaks are in the Cardinalidae family, which of course include cardinals.