Yellow-rumped warblers become brighter for breeding

Area songbirds are slowly but steadily molting into their breeding plumage. For some the transformation from winter basic plumage to breeding plumage is striking. I have written about the changes American goldfinches go through; anyone who has enjoyed that species knows well the change from dull greenish to bright yellow and black that the males go through.

Another species that experiences significant plumage change is the yellow-rumped warbler. For the past month or so I have enjoyed watching a small group of three individuals at my feeders slowly molt into striking breeding plumage. They aren’t done yet either; they’ll probably take another couple of weeks to attain the superior look.

Along with the pine warbler, the yellow-rumped warbler is one of two members of the wood warbler clan that winter in numbers in the Piedmont of the Carolinas. They can survive our winters because they can eat and digest berries of the wax myrtle. They also benefit from other winter small berries and any small invertebrates they find on tree trunks and foliage. In coastal areas where wax myrtle is abundant, it is easy to see hundreds in a day. Early winter through February they are infrequent feeder visitors, but by March, when the food supply dwindles, I start seeing them constantly visit my suet dough feeders.

They are a nondescript winter bird, often overlooked by casual observers. You have seen them and heard their chirps, but they are hardly eye-catching. Various shades of gray from whitish to darker streaking on the flanks and breast is the look. The exception is two yellow patches on the sides of the upper breast and a patch of yellow on the rump. With a good look, these patches can be seen but may be a muted yellow in some individuals.

By mid-April the hues have changed to a subtle beauty of contrasting blue-gray, black and white. The yellows have deepened and intensified against the gray and black background. Add a yellow patch right on top of the head and the transformation is complete. They become very vocal, too, giving a sweet, high-pitched warble throughout the day. You have heard that, too.

And then they leave. The destination is cool coniferous forests of the high elevations of the Appalachians on up into Canada. When they return in October, the adults will be back in duller garb, with immature birds even more nondescript.

This story was originally published April 12, 2018 at 12:45 AM with the headline "Yellow-rumped warblers become brighter for breeding."