Know your coffee birds: Black-throated Blue Warbler

by on December 9, 2008

The North American Wood Warblers are known for their colorful beauty. The male Black-throated Blue Warbler (Dendrioca caerulescens, left) is one of the most beautiful. This species is one of the most sexually dimorphic as well — the female is not blue at all — and was not even recognized as the same species until the late 1800s. The pale “hanky” showing on the lower edge of her wing, which matches that of the male, is the only giveaway.

This eastern warbler nests in large forests in the northeastern United States and southern Canada and in higher elevations of the Appalachian Mountains. They spend the winter mostly in the West Indies, as well as along the Caribbean coast of the Yucatan, Belize, and Honduras. New techniques using a simple laboratory test of the molecular composition of feathers has revealed that Black-throated Blue Warblers from the northern part of the breeding range winter mostly in Cuba and Jamaica, and birds that nest in the Appalachians winter mostly in Hispaniola and Puerto Rico [1].

A common species in shade coffee ecosystems
Wintering Black-throated Blue Warblers are frequently found on coffee farms, with studies noting them using these plantations in Jamaica, Puerto Rico, the Dominican Republic, Haiti, and Chiapas, Mexico. These studies often note that Black-throated Blue Warblers are one of the most common migrants found on the farms.

While wintering in coffee farms, Black-throated Blue Warblers consume primarily small insects, many of which are coffee pests. In Jamaica, Black-throated Blues were the number one predator recorded on the dreaded coffee berry borer.

Like some other species of wintering migrants, Black-throated Blues tend to segregate themselves by sex on their wintering grounds. Males tend to be found in tall, mature forest habitat, and females in shorter, shrubby habitat. Research has shown that in the Dominican Republic, shade coffee farms had more males than females [3,5], indicating that shade coffee farms were a good substitute for tall forest habitats.

Many bird species return to the same places to nest each year, and some also return to regular wintering areas. Black-throated Blue Warblers are very faithful to their wintering sites [2,3]. In fact, they have a stronger fidelity to their winter territories than their nesting territories, making the health of the habitats on coffee farms critical to their survival [4]. Declines in abundance of breeding populations in the southern Appalachians of over 2% a year the last two decades may be linked to severe habitat degradation in parts of the winter range, particularly Haiti [1] where deforestation is particularly severe.

The Black-throated Blue Warbler’s song is sometimes described as sounding like a buzzy “beer-beer-beer!” From its strong affiliation with shade fincas in the winter, we know what it really means is “coffee-coffee-coffee!”

[1] Rubenstein, D. R., C. P. Chamberlain, R. T. Holmes, M. P. Ayres, J. R. Waldbauer, G. R. Graves and N. C. Tuross. 2002. Linking breeding and wintering ranges of a Neotropical migrant songbird using table isotopes. Science 295: 591-593.

[2] Wunderle, J. M., Jr. 1995. Population characteristics of Black-throated Blue Warblers wintering in three sites in Puerto Rico. Auk 112: 931-946.

[3] Wunderle, J. M., Jr. and S. C. Latta. 2000. Winter site fidelity of nearctic migrants in shade coffee plantations of different sizes in the Dominican Republic. Auk 117: 596-614.

[4] Holmes, R. T. and T. W. Sherry.  1992.  Site fidelity of migratory warblers in temperate breeding and Neotropical wintering areas: Implications for population dynamics, habitat selection, and conservation. pp. 563-575. In: J. M. Hagan III and D. W. Johnston (eds.). Ecology and Conservation of Neotropical Migrant Landbirds. Smithsonian Institution Press.

[5] Wunderle, J. M., Jr. and S. C. Latta. 1996. Avian abundance in sun and shade coffee plantations and remnant pine forest in the Cordillera Central, Dominican Republic. Ornithologia Neotropical 7: 19-34.

Top male Black-throated Blue Warbler by Jerry Oldenettel; bottom by Julie Craves.

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Revised on March 23, 2014

Posted in Birds and other biodiversity,Know Your Coffee Birds series

Julie December 11, 2008 at 4:26 pm

Well, they would not make good pets and in the U.S. it would be illegal to possess them. I just like admiring them in the wild.

Jamaican Blue Mountain Coffee December 11, 2008 at 3:25 pm

I wonder if I could get one as a pet. I had never heard of coffee birds before, but I'm pretty interested in them now.

SL28ave December 14, 2008 at 7:27 pm

I'll keep my eyes open for them when hiking in the Appalachians in the summer… and if I ever take a lucky warm break in the Panamanian "winter".

Andrew - Medical Encyclopedia January 21, 2009 at 4:10 am

me too, I've never heard about coffee birds… that sounds so exotic! you know, it's interesting from where did it get its name because t first I thought it will be of that beatiful coffee-brown color, but it looks more blue)))

Archie - Forex Forum January 22, 2009 at 5:23 am

coffee birds… hm… I googled, I searched in Wikipedia but i didn't ind anything about this bird… is it a truly exeisting one? or is it a piece of mystery like the Firebird?

BirdBarista January 22, 2009 at 8:30 am

The name of this bird, Black-throated Blue Warbler, is noted repeatedly in this post. My term "coffee birds" in this series refers to species that are frequently found on coffee farms. It is a generic term much like you would use "forest birds" or "urban birds."

Michael January 22, 2009 at 2:35 pm

Many of us can pinpoint the awakening of our inner birder to an early encounter with a then-unknown bird, discovered close to home. Mine came with the Black-throated Blue Warbler, actually a pair of these little birds, foraging in a forest understory in the Thousands Islands region, only a few metres from my path.

Without binoculars, I could clearly see the white patch at the base of the outermost primaries. Once home, I cracked open the family Peterson guide and there it was. I was hooked. Within weeks, I had identified a dozen more warbler species.

My first taste of coffee came some years later and again, I was hooked…but that's a story for another day.

It's good to read about efforts to maintain suitable winter habitat. We make a point of only buying bird-friendly beans.

Thanks for sharing this.

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