If you're reading this on May 10th — Happy Mother's Day! If you're reading it on the 11th, I apologize for being a day late. I took these pictures today, 10 May 2015, at Crane Creek Regional Park in Santa Rosa.
Above, a juvenile White-breasted Nuthatch has its bill wide open, ready to receive food from its parent — probably its mother, based on the paler gray (not black) crown.
Here's the next scene:
I encountered some nuthatches in an oak tree, and heard lots of soft, twittering sounds, making me suspicious that there could be juveniles around. I couldn't locate a juvenile at first, and then I finally found one sitting quietly — see below, and note the yellow bill color.
I wondered, if I waited long enough, whether I'd see an adult bring food to the juvenile. Sure enough, I saw two separate feeding events.
Here's the second one (I think this was the father, with a black crown):
I haven't seen juvenile White-breasted Nuthatches that often. So I took a few pictures to document some of their characteristics.
I mentioned the bill color (yellow in juveniles, gray in adults). The bill length is different, too — shorter in juveniles. Compare them in the next picture:
Note the softer-looking plumage, and the paler and more restricted crown of the juvenile (i.e., there's more white on the back of the neck):
To my eye, the juvenile had grayer underparts (see below). (And I was surprised to see that the juvenile already had rusty undertail coverts!)
The Birds of North America account mentioned that juveniles may have back feathers with dark tips and scapular feathers with light tips. I couldn't make out that patterning on the back feathers. I could see light tips in the shoulder region, creating a thin, pale bar:
Although I observed this juvenile being fed by the adults, I also saw it (or a different individual) foraging on its own. (Note the short bill.):
Interestingly, I thought I might have counted 3-4 birds in the tree at first, but it was hard to keep track as they moved among the dense oak leaves. When this flock left the tree, at least 8 nuthatches flew out! Later I read that the average clutch size is 6.4. Young nuthatches may stay with their parents for several weeks after leaving the nest.