Birds and other biodiversity

The Tennessee Warbler (Vermivora peregrina) is a great example of a “Neotropical migrant”: a bird that breeds in North America and winters in the tropics. They can be common to abundant during migration over a wide swath of the continent (including Tennessee, where it was discovered, resulting in the rather inappropriate name). Tennessee Warblers are one of the classic winter residents of shade coffee farms in Central America and northern South America, which led tropical ornithologist Alexander Skutch to conclude that they really should be named “Coffee Warbler.”

A Tennessee Warbler in winter in the Costa Rican highlands.

Tennessee Warblers nest across the Canadian boreal forest. They are one of the warblers that specialize in spruce budworms. In years when these insects are abundant, populations of the warbler swell. In fact, Tennessee Warblers are one of the most important predators of these devastating pests.

On their wintering grounds, Tennessee Warblers like semi-open to open second growth forest, and shade coffee plantations share the habitat characteristics of these forests. On coffee farms, Tennessee Warblers are often associated with flowering trees, especially those in the genus Inga, which are very common on shade coffee farms. Although the warblers may defend a flowering tree, they are also often found in mixed species flocks. Since Ingas do not flower for a long period of time, these flocks may track the flowering trees across the landscape. The warblers also fond of  two other tree genera frequently used as shade trees on coffee farms, Erythrina and Grevillea.

Why do the warblers like the flowering trees? Winter is dry season in the tropics, when insects are less abundant. Nectar becomes and important part of the winter diet of Tennessee Warblers. For this reason, shade coffee farms are considered very important to the survival of this little bird with the understated colors and loud, ringing voice.

Read more:

• The Coffee Warbler (Smithsonian Migratory Bird Center, by my friend Tom Dietsch.
• Tennessee Warbler (Boreal Songbird Initiative)

Photo of Tennessee Warbler by Jerry Oldenhettel. Range map from All About Birds, Cornell Lab of Ornithology.

I’d like to inaugurate my “Know your coffee birds” series with the bird Coffee & Conservation uses to rate coffees (e.g., a “five star” coffee here is a “five motmot” coffee): the Blue-crowned Motmot (Momotus momota).

Motmots are a family of New World tropical birds related to kingfishers. Like kingfishers, they nest in burrows which they dig themselves into soil cliffs or road cuts; these burrows are five to up to 14 feet long, and winding. Most motmots are medium-sized (robin size or larger), and are sit-and-wait predators of large insects, small reptiles or mammals and similarly sized prey, along with a little fruit.

The Blue-crowned Motmot is the most widely distributed motmot, and is found from Mexico to Argentina in lowland forests, on up to 1300 meters. It’s fairly tolerant of somewhat disturbed habitats, and thus can be found in open woodlands and second-growth forest such as those found on shade coffee plantations.

Blue-crowned Motmots are about 42 cm long (17 in). Like other motmots, they have a unique spatulate tail. When the new tail feathers grow out, they have an appearance like most other long-tailed birds. But a portion of the lower section of the two center feathers have weakly-attached feather barbs, so these barbs fall off the shaft in short order. This creates a bare stretch of feather shaft, with a paddle-shaped tip at the end. There is evidence that male motmots with longer denuded sections are more attractive to females.

This is peculiar enough, but motmots also swing the tail like the pendulum on a clock, generally in the presence of predators. Despite their size, motmots are often difficult to see until they start wagging their tails. Drawing attention to themselves when a predator is near seems counter-intuitive, but this behavior actually serves to deter the types of predators most likely to go for a motmot: those that rely on stealth and ambush. In essence, a motmot is signalling, “Hey, I see you, and you can’t surprise me.” Ambush predators tend to abandon the hunt when they know they’ve been detected.

I’ve seen several species of motmots in the tropics, including Blue-crowned Motmots at Finca Hartmann. They are among my all-time favorite birds, and a fitting mascot for great sustainable coffee.

Look for more profiles of birds found on coffee farms in the coming months. Many will be species that you can find much closer to home.

Murphy, T. G. 2006. Predator-elicited visual signal: why the turquoise-browed motmot wag-displays its racketed tail. Behavioral Ecology 17:547-553.

Murphy, T. G. 2007. Dishonest preemptive pursuit-deterrent signal? Why the turquoise-browed motmot wags its tail before feeding nestlings. Animal Behaviour 73:965-970.

Murphy, T. G. 2007. Racketed tail of the male and female turquoise-browed motmot: male but not female tail length correlates with pairing success, performance, and reproductive success. Behavioral Ecology and Sociobiology 61:911-918.

Photo of a Blue-crowned Motmot via Wikimedia Commons.