Q: Here's a mystery for you: During a dry period I noticed a robin in my backyard with what looked like mud all over its chest, and later I found that our birdbath was very muddy. What was going on?

A: The muddy robin you observed was almost surely a female during the busy days of building her nest. After she'd built a base of plant fibers and twigs, the robin gathered up balls of dirt in her beak and stopped at your birdbath to wet it down (since there was no ready-made mud available). Then she flew to her nest and packed the mud down to create nest walls.

She got muddy herself as she squatted and turned in the nest to tamp the mud into place and make sure the space was a good fit, important as she faces two weeks of incubation duty.

Robin nests are heavy and well-built; sometimes a female will re-use an old nest as she begins the second brood.

Unusual feeder birds?

Q: I noticed some yellow-rumped warblers at my suet feeders in early May, something I've never seen before. Is this unusual?

A: The prolonged cold weather this spring drove many of these warblers to bird feeders when they couldn't find the insects they usually feed on. Readers reported seeing warblers eating suet, seeds and even peanut bits. One reader sent a photo of a yellow-rumped warbler eating the grape jelly she'd put out for orioles. Flocks of the warblers also foraged in the street, apparently eating seeds that dropped from boulevard trees.

This is the earliest warbler species to arrive in our area, and their survival strategy includes being willing to try new foods.

Different eagle

Q: I saw what I think is a golden eagle perched in our big oak tree. It wasn't a bald eagle or a hawk, because I know those, and it was the biggest bird I've ever seen.

A: I'm going to suggest that you were seeing a young bald eagle, for several reasons. For one, you mentioned that you live near a lake, and this is the kind of habitat preferred by bald eagles. Golden eagles, however, aren't attracted to water, instead feeding on inland prey, like rabbits and squirrels. Young bald eagles don't look like our idea of bald eagles. They're big, brown birds lacking an adult's distinctive white head and tail — they don't develop these until they're five years old. So I'd put my money on a young bald eagle, always a nice sight to see.

Food-sharing birds

Q: When a bird feeds another as part of a courtship ritual, is it usually the males feeding females or do both of them do this?

A: This kind of behavior is found in many species of birds, and it almost always is the male feeding the female. There are various theories about why birds such as cardinals, goldfinches, towhees, waxwings and nuthatches do this, but it seems to be related to courtship. The male may be seeking to show the female that he'll be a good provider for their nestlings, and this behavior seems to strengthen the bond between them. Food-sharing behavior is found mainly in species in which both parents care for their young.

Chickadee wars

Q: I recently encountered two chickadees in a major dust-up, locked claw to claw and tumbling down my driveway. They separated and re-engaged a couple of times, while fellow chickadees flew in and out of the fracas. Any ideas for what caused this spectacle?

A: I've never seen 'dees engage in such ferocious behavior, but even though they're tiny birds, they can be very feisty. A couple of possibilities spring to mind: In one scenario, these were males battling over territory. Chickadees nest in cavities and there never are enough of these to go around, so one bird might be trying to prevent another from occupying a tree hole.

Another possibility is that a male chickadee was attempting to force a female to allow him to mate with her, an act called forced copulation. The other chickadees might have been attempting to participate in this, as well.

Woodpecker abundance

Q: We seem to have a great abundance of woodpeckers at our feeders this spring. Any special reason for this?

A: I'll bet the reason you notice so many woodpeckers can be traced to the birds having had a very good fall and winter. You can take credit for helping boost their survival rate by maintaining many feeders and keeping them filled.

St. Paul resident Val Cunningham, who leads bird hikes for the St. Paul Audubon Society and writes about nature for local, regional and national newspapers and magazines, can be reached at valwrites@comcast.net.