I was surprised because it seems early to see a rose-breasted grosbeak
so far north. I
have Peterson's east of the rockies bird guide and I checked the bird
to make sure it wasn't a finch. But I'm afraid I didn't even think to
check if it was a black-headed grosbeak.
I am pretty sure it was a grosbeak. The bird was probably 50% bigger
then the purple finch that visited a few minutes later. The markings
on the breast were much more prominent then I've seen on female
finches and the beak to head ratio seemed larger then for finches. I
didn't get a good look at it's head to see whether or not there was a
band over the eye though because the bird was fairly shy.
From a quick internet search it looks like the female black-headed and
rose-breasted have very similar markings. I didn't see any buff
coloring on the breast, but I'm not sure that's a solid indicator of
which it was. I'll put my camera next to the bird window and if I see
it again I'll try and get a photo.