
Throughout this season and the previous winter, I have talked here in this blog about plumage details of Golden-cheeked Warblers: how to separate this species from closely related warblers, and within the species how to distinguish the various sex and age classes.
Let's take that last subject to another level. I believe the bird pictured above is an adult male, most likely a second-year male.

But look more carefully at the top photo. One of things that's notable in that photo is that the mantle or upperparts are not entirely black. The crown and eye stripe appear black, but the mantle seems dark olive with thick black streaks. That last field mark is better for adult female or a younger male. Adult females and first winter males, however, don't have black chins.


So what we have here is a bird that shows some field marks for an adult male, and some for a younger bird.

I photographed this bird in the morning of January 31, 2010 near Monte Uyuca in Honduras. Over lunch that day, I looked at these photos with my field assistants Kashmir and Fabiola, and with Salvadoran banders Roselvy and Lya. For Roselvy, one of the most experienced banders in Central America and someone well versed in the subtle art of looking at plumage details on warblers, it was clear that this bird had to be a second year male.
During previous field seasons, I sometimes wondered whether it's really possible to separate immature males from adult females in the field. This year, with more field experience with the species, I felt more comfortable assigning sex and age classes to the birds we saw. In some cases, we saw the bird only briefly or from a distance, but in most cases we were able to observe the birds for extended periods of time and from various angles. Paying close attention to plumage details helped us separate different individuals in the same warbler flock, even if we didn't get the opportunity to see them feeding side by side.
This weekend I'm set to count shorebirds in western El Salvador. This will be the fourth year of this count, and the second year of my participation in it. This shorebird count is organized by the Salvadoran Ministry of Environmental Affairs, and each year is repeated in April. I'm hoping our team - Roselvy, Karla and me - will find some interesting species! We're going to do this without a telescope, only binoculars, so finding the rarer species will be quite a challenge...
Shorebirding is very different from following a mixed warbler flock in a forest, yet here too it pays to look for plumage details, as well as structure and behavior. Monday I'll be traveling, but I should be able to post some shorebird photos around mid-week.
No comments:
Post a Comment