Two types of black-throated warblers number among New World bird family

Photo by Skeeze/Pixabay.com The female black-throated green warbler lacks the male’s all-black throat, but she is a striking bird in her own right. Black-throated green warblers and the related black-throated blue warbler are common birds in the Southern Appalachians from April to October.

I’ve enjoyed some lawn chair birding on recent September evenings, delighting in my observations of birds ranging from flycatchers and catbirds to warblers, vireos and hummingbirds. I enjoy my casual study of the daily changes in the bird population present in my yard and adjacent woods. The parade of warblers hasn’t been as productive as in past autumns, but I have managed to spot and identify hooded warbler, American redstart, chestnut-sided warbler, magnolia warbler, Northern parula, and black-throated green warbler visitors.


The black-throated green appeared suddenly in a fast-paced burst of foraging in a cherry tree. Alongside birds such as an Eastern wood-pewee and red-eyed vireo, the warbler gleaned the leaves of the trees for concealed caterpillars. I watched the bird swallow with gusto several of the caterpillars so skillfully plucked with its thin, pointed bill.

The black-throated green warbler and one other species, the black-throated blue warbler, share the appellation of “black-throated,” and rightfully so. Males in the spring look their best with a dark black throat in striking contrast to the rest of their plumage. The female black-throated green shows some black on the throat, but female black-throated blue warblers exhibit no black throat patch. In fact, black-throated blue males and females are extremely different in appearance. Scientists call such dramatic appearances differences “sexual dimorphism.” Among the warblers, this species provides the most striking example of sexual dimorphism of any of the warblers. The male and female do share one identifying mark — a white square near the outer edge of the middle of each wing. This square is usually more pronounced in the male, but it stands out enough that it helps distinguish the female black-throated blue from similar dull-plumaged birds such as vireos. 


German naturalist Johann Friedrich Gmelin described the black-throated blue warbler in 1789. I noted in last week’s column that Gmelin woefully misnamed such warblers as palm warbler and magnolia warbler. With the black-throated blue warbler, Gmelin did a better job. This bird’s scientific name name is the Latin term caerulescens, which translates into English as “turning blue.” The male is a stunning bird. Arguably, the black-throated blue warbler is one of the most distinctive members of the family of wood warblers. The adult male has a black face and cheeks, deep blue upperparts and a clean white underbelly. In contrast, the adult female is olive-brown above and light yellow below. 


When one’s binoculars first focus on a black-throated green warbler, the first impression is likely to be the black, yellow and white feathers in the bird’s plumage. The greenish-yellow coloration that gives this species part of its common name is mostly limited to the bird’s back, which is often not as evident when the bird’s being watched through binoculars.  
Both of the black-throated warblers nest in northeast Tennessee, western North Carolina, and southwestern Virginia. In the spring, the males of both these warblers are persistent singers from prominent perches in the green woodland canopy. Male black-throated greens contribute to the avian chorus by frequently singing a high-pitched song often described as a buzzy zee-zee-zee-zooo-zeet. Male black-throated blues produce a buzzy zee-zee-zeeee. 

The black-throated green warblers currently departing the region will likely travel as far as Mexico, Central America, the West Indies and southern Florida for the colder winter months. Black-throated blue warblers, on the other hand, migrate to the Caribbean for the winter, making their homes on Cuba, Jamaica, Hispaniola and Puerto Rico, as well as other islands. 
Nearly half of the world’s New World warblers spend the months between spring and fall in North America. The other half reside exclusively in Central and South Americas, as well as the Caribbean. Some of the more descriptively named individuals residing in the tropical areas south of North America include flame-throated warbler, crescent-chested warbler, arrowhead warbler, white-rimmed warbler, buff-rumped warbler, golden-bellied warbler, fan-tailed warbler, pink-headed warbler and pale-legged warbler. 


The warblers bring some exciting tropical flair into the hills and hollows of Southern Appalachia for several months every year. I miss them once they’re gone for the winter season, but the promise of their return keeps my spirits buoyed during the cold, darker months until spring. 

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