05222021 FEATHER - A male chestnut-sided warbler

A male chestnut-sided



By Bill Chaisson

Until the indigo buntings showed up last week, the chestnut-sided warblers were the loudest, most persistent singers in the hillside meadow behind our cabin. They have at least two different songs, and I did not figure out on my own what occasion causes them to deploy one versus the other. I know that I have at least two pairs because there is an ongoing and occasionally bitter dispute going on along the woods road that leads up the hill on the north side of the meadow.

I describe it as a “meadow” even though there is not much grass in it as yet. The landowner seems to have cleared it of trees and brush sometime in the last five or ten years and then let the forest close in a little along the edges, creating a band of dense saplings—mostly white birch—that chestnut-sided warblers adore.

My indelible memory of this species is, oddly enough, from my sojourn in Carroll Gardens in Brooklyn. This neighborhood is just behind Red Hook (and actually used to be part of it, before the Brooklyn-Queens Expressway cut it in half; thank you Robert Moses), which sticks out into New York Harbor just below Manhattan. As such it is a convenient stop for birds migrating north in the spring. After a long night of flying up the East Coast, the mature trees that line the streets between the brownstones are a welcome sight.

I lived on the third floor of a brownstone with a large Norway maple in front of it. I woke up one May morning just as that tree was leafing out and looked out the window of my bedroom to see the canopy absolutely crawling with chestnut-sided warblers. This was in 1987 or ‘88, over 30 years ago, when there were more warblers than there are now. The chestnut-sided warbler has not been hit as badly as some, but it declined by 1.2% between 1966 and 2015, according to the North American Breeding Bird Survey, for a cumulative loss of 45% of the population. Some of this is due to the decline of small-scale agriculture and the succession of neglected fields to forest.

My local chestnut-sided birds arrived in my meadow on May 8. (I have a calendar in the kitchen where I mark the first appearances of species.) Last week I noted that I was still waiting for the expected black-throated blue and Blackburnian warblers, and they have indeed arrived. (I had hoped to have magnolia warblers but, apparently, we don’t have quite enough hemlocks right around the house.)

Both the black-throated blue and Blackburnian warblers live in the forest, and they also have much higher-pitched songs that the chestnut-sided, so it is the latter I hear from inside. To hear the other two, I have to hike up the woods road and stand at the edge of the coniferous-deciduous forest.

The black-throated blues have two songs as well, but I rarely hear the wheezy one around here. Instead, the male I hear likes the four or five notes delivered at progressively great volume followed by a high-pitched lisping wheeze. The Blackburnian also has two songs, and, again I have mostly heard just one of them. The notes are even higher pitched than the black-throated blue and delivered much more rapidly and with accelerating speed, which then ends in a wheeze so high pitched that some people cannot hear it. Happily, I still can, probably because I didn’t embrace listening to a Walkman in the 1980s.

In contrast, I regularly hear both songs of the chestnut-sided warblers, and I also see two males literally chasing each other around. Interestingly, the dispute has not escalated into a physical altercation, as it does with some more pugnacious birds, like robins or song sparrows. The male chestnut-sided responds to trespass by flying directly at the interloper, who will give ground after the briefest of stand-offs. The retreat takes the form of hopping from limb to limb for a couple of seconds and then fleeing to another tree. The territory proprietor does not immediately pursue the trespasser, but lets a few beats go by to see if the intruder will depart on his own. It is during this brief cessation that the homeowner may nervously sing a snatch of song. Then he flies at the foreigner and the whole thing starts all over again.

The song of the chestnut-sided warbler has been rendered as “pleased, pleased, pleased ta meetcha!” at least since Roger Tory Peterson’s guide from the 1930s. Peterson also noted the existence of a second, similar song that lacked the accent, a sudden down-scale slur, at the end (represented by the exclamation point). According to allaboutbirds.org, the chestnut-sided sings the accented song more often earlier in the nesting season while it is actively defending its territory from other males. It switches to deploying the unaccented song (which resembles that of a yellow warbler) more often later in the summer. I hear this second song as “suwee, swee, ch-ch-ch-chew” and already I hear it a lot.

Only the bay-breasted warbler also sports chestnut sides, but its chestnut extends up onto its throat and to the nape. In contrast, the chestnut-sided warbler has a bright yellow cap and a black-and-white striped nape. The female closely resembles the male, but her colors are duller and her chestnut siding less extensive.

These birds often hold their tails cocked and are nearly as bold as house wrens. During their quarrels, the males seem almost oblivious to my presence; I get close enough to hear the whir of their wings, although they remain blurs of motion.

I have seen one female near a clump of birches that projects out into the meadow, separated from the forest edge by the woods road. I suspect her nest, usually only a few feet from the ground, is there.

Bill Chaisson has been a birdwatcher from the age of 10. He is a former managing editor of the Eagle Times and now lives and works in the town of Wilmot. Contact him at wpchaisson@gmail.com.

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