Gnatcatchers

by Mike Scully

This article first appeared in the March 2004 issue of the San Antonio Audubon News.

Long, long ago, on a canoe trip far, far away, a couple of high school friends and I loaded up my canoe, fired up the little outboard and motored out up the Hudson River, stopping for the night to camp on an isolated, wooded stretch. Thirty years later, only scattered images of that trip remain, but I do remember waking up in the June woods at sunrise and hearing a thin, wheezy warble from somewhere up above. Looking up, I saw a tiny blue-gray bird flitting around in the airy green foliage of a beech sapling. Gnatcatchers weren’t that common so far north, and as I recall that was my first.

I am still happy every time I see one of these graceful little birds; certainly they are among the more aesthetically pleasing of our avifauna, possessing both an attractive form and lively habits. The moniker “gnatcatcher” refers to their frequent sallying out to capture small insects in flight, although they also glean insects from foliage. The genus name Polioptila translates from the Greek to “gray feather”, delicate shadings of gray being the prevalent color among the ten species in this genus. In appearance, gnatcatchers are not unlike tiny Mockingbirds, and it has been suggested that the gnatcatcher habit of frequently fanning and raising their black and white tails might function to flush prey, much as the white wing patches of Mockingbirds are known to do.

As so often seems to be the case with ‘our’ North American birds, the gnatcatchers as a group are primarily tropical, six of the ten species in the genus inhabiting ranges far to the south of our area. All four of the species known to breed in the USA also breed south of the border, down to Central America in the case of our familiar Blue-gray Gnatcatcher (P. caerulescens). Although it didn’t occur to me at the time, that long-ago New York gnatcatcher was near the northern edge of a vast array of generally similar gnatcatchers stretching clear to Argentina.

Had I taken the time to look, I might have located close by in those woods a typical gnatcatcher nest; a tiny cup of fine plant materials bound together and attached to a branch with spider webbing. Likely there was a mate close by, too, gnatcatchers commonly foraging in pairs in a jointly-defended breeding territory. One brood of four to eight young is the norm for Blue-gray Gnatcatchers in the north, southern birds often raising a second brood. The northern populations of this species are of necessity migratory. Gnatcatchers inhabiting warmer climes, including the southernmost populations of the Blue-gray, are generally sedentary.

This non-migratory status certainly applies to the Black-tailed Gnatcatcher, which is even smaller than the Blue-gray, and which replaces it as a breeding bird in the arid deserts of the Southwest. Very similar to the Black-tailed, but barely reaching our area, is the Black-capped Gnatcatcher (P. nigriceps). The chance of finding this species in the US being one of the possibilities that makes the southeastern area of Arizona so attractive to birders.

Our fourth species, the California Gnatcatcher (P. californica), was once considered conspecific with the Black-tailed. Found in coastal sage scrub from Southern California down into the Baja, the 1989 restoration of this bird to full species status was followed by a storm of controversy when conservation groups petitioned USFWS for federal protection of the dwindling populations of a California subspecies (C. c. californicus). The species, which occupies some areas of potentially valuable real estate, was officially listed as “Threatened” by the Federal Government in 1991.

Sources and More Information:

http://animaldiversity.ummz.umich.edu/site/accounts/classification/Polioptila.html
http://museum.nhm.uga.edu/gawildlife/birds/passeriformes/pcaerulea.html
http://www.arthurgrosset.com/sabirds/maskedgnatcatcher.html

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