Blackburnian Warbler
Setophaga fusca
Compiled by Yvonne Karnath
Some birds you have to work for in Central Texas. The Blackburnian Warbler is one of them. It does not breed here, it does not winter here, and on a typical year a Travis County birder might pick up just one or two individuals during the brief spring rush in late April and early May, when migrants are pouring north out of the tropics and onto our oaks for a few hours of feeding before continuing on. But when you finally find one — usually near the top of an oak, ten or twelve seconds before it vanishes again — it stops you cold. There is no other warbler in North America that wears that color on its throat.
The adult male Blackburnian is, frankly, on fire. The throat and upper breast glow a hot, saturated orange that field guides have struggled for a hundred years to describe — “flame,” “tangerine,” “molten,” “torch-like.” The crown is the same orange. A bold black mask runs through the eye and back to the nape, surrounding an orange triangle on the cheek. The back is black with two clean white stripes, the wings are black with a large white wing patch, and the belly is pale, lightly streaked along the flanks. Cornell’s All About Birds notes flatly that “no other North American warbler has an orange throat.” It is one of the easier birds in the family to call as soon as you see it.
Females and immatures wear the same pattern in a quieter key. The throat is yellow rather than orange, the black mask is replaced with olive, and the back is olive-streaked rather than black. Even so, the head pattern — pale supercilium, dark eye-line, pale crescent below the eye — and the two white wing bars are diagnostic. The flank streaking is fine and limited. If you are sorting through a flock of fall warblers and one shows a clear yellow throat with a dark olive triangle on the cheek, you almost certainly have a Blackburnian.
The species is small even by warbler standards, just over four inches long, weighing about the same as four pennies. That little body makes one of the longest migrations of any North American wood-warbler. Breeders in the mature spruce-fir and hemlock forests of New England, the Appalachians, the Great Lakes, and across boreal Canada head south every fall to the cloud forests of the northern Andes, where they spend the winter in mixed-species flocks at five to eight thousand feet. The northbound spring route brings most of them across the Gulf of Mexico, and a small fraction of that flight passes directly over Central Texas.
The breeding-season life history is, in a word, vertical. Blackburnian Warblers nest near the tops of large conifers — often more than fifty feet up — and they spend most of their foraging time in the upper canopy too. This is the bird that gave field ornithologists in the 1950s their textbook example of how warblers partition vertical space within a single tree: Robert MacArthur’s famous study of five warbler species in northeastern conifers placed the Blackburnian almost exclusively in the topmost branches, while Yellow-rumped, Black-throated Green, Bay-breasted, and Cape May warblers worked the layers below. The result is that even on the breeding grounds, where the species is locally common, most of what birders see is the underside of a singing male against the sky.
The song is high, thin, and easily missed if you have any age on your ears. It is a fast series of rising notes ending in an upward sliding trill, somewhere around 8 to 10 kilohertz — close to the upper edge of human hearing. On migration through Texas, Blackburnians very rarely sing, and you are almost always picking them out by the orange throat or, on quieter days, by their soft, dry call note.
Where to look in Travis County? Spring is the realistic window — late April through about the second week of May — and the best places are the same migrant traps that produce the year’s good warblers in general. Hornsby Bend, Commons Ford Ranch Metropolitan Park, Roy Guerrero Park, the Wild Basin Wilderness Preserve, and the Mueller area’s wooded edges have all turned up Blackburnians in recent years. Pay extra attention to the very tops of large oaks, especially after a south wind followed by a rainy night, which can drop migrants out of the sky in noticeable numbers. Fall records exist in our area too, but they are scarcer and the birds are duller, so spring is when you have your real shot.
Conservation status, for now, is reassuring. Breeding Bird Survey data show Blackburnian populations stable across most of their range, with some regional declines tied to logging of mature conifer forests and to ongoing habitat loss on the wintering grounds in the Andes. The species is not currently listed by Partners in Flight as a watchlist bird, but it is a useful reminder of how much our springtime warbler waves depend on forests we will never see — boreal Canada in summer, Colombian and Ecuadorian cloud forest in winter, and a thin band of Texas oaks in between.
Spend one good morning in late April standing under a live oak at Hornsby Bend and looking up. If you are lucky, somewhere in the canopy a small bird with a throat the color of a struck match will work its way along a branch for a few seconds and then be gone. That is your bird, and it is on a journey that started in the Andes and is not finished yet.
Sources:
https://www.allaboutbirds.org
https://ebird.org
https://www.audubon.org/field-guide/bird/blackburnian-warbler
https://www.fws.gov/species/blackburnian-warbler-setophaga-fusca
Photo Credit: Shirley Donald, Alan Zhou, Lori Malloy
