BLACK-THROATED BLUE WARBLERS ON ABACO

It’s warbler time of year on Abaco, and a good time to take a look at the Black-throated blue warbler Setophaga caerulescens. This small warbler has very particular breeding and overwintering ranges. In the summer they are found in the forests and woods of eastern North America. As the Fall approaches, they start to migrate south to the Caribbean and Central America. Abaco is one of their winter homes, as well as a likely transit stop on their way further south. Right now sightings are being reported on the mainland and the Cays.

WHAT DO I LOOK OUT FOR?

Males and females are quite different in appearance (‘sexually dimorphic’), and could even be mistaken for distinct species. Males are a deep slate-blue above (hence caerulescens) with a striking black face and throat, and white underparts. They are unmistakeable, and unlikely to be confused with any other warbler. Females are basically grayish-olive above and pale yellow underneath. For ID, look for a white stripe above the eye, a pale arc below it. In addition, both sexes have a diagnostic white patch on the the wing.

The bird cartoon site Birdorable as usual has a spot-on comparison of the sexes

These pretty warblers can be seen in gardens, coppice, and woodland. Although mainly insect-eaters, sometimes catching them in flight, they also eat fruit and seeds especially in winter. BTBWs are territorial, and will defend their chosen space against all-comers, including their own species.

WHAT DO I LISTEN OUT FOR?

One source asserts: “The bird’s song can be described  as a buzzed zee-zee-zeeee with an upward inflection. Its call is a flat ctuk”. See what you think…

SONG Etienne Leroy / Xeno-Canto

CALL Paul Marvin / Xeno-Canto

ARE BTBWs THREATENED?

BTBWs are fairly common birds within their range, with a large population. The usual stuff is happening with them in terms of habitat destruction & co at both ends of their migration. For some already threatened species (e.g. Kirtland’s Warblers), habitat degradation at either end of the migration (let alone both) presages a downward spiral in population. With BTBWs, I have read both that the population is decreasing; and in another source, slightly increasing. For now, let’s regard the welfare of the species as being stable. However, the current causes of species decline will doubtless continue, and many regard increasingly evident climate change as being a determining factor for the well-being of migratory species. The birds are not yet out of the woods, so to speak… and maybe never will be.

CREDITS Photos: Gerlinde Taurer (1, 2); Becky Marvil (3); Bruce Hallett (4); Blaine Rothauser / CWFNJ (5); @daxroman / Birds Caribbean (7); Paul Reeves / Birds Caribbean (8).  Range Map, Wiki; Cartoons,  Birdorable; Video, Cornell Lab for Ornithology