The Cozumel Thrasher – T. guttatum
If Not Already Extinct, Mexico’s Most Endangered Bird
Once there were thousands of Cozumel Thrashers on Cozumel Island, but they've declined so precipitously that they may actually be extinct.
Thrashers belong to the mockingbird family, found from southern Canada to southern Argentina. The Cozumel Thrasher, Toxostoma guttatum, is found only on the Mexican Island of Cozumel, where it was once very common. Today, if it exists at all, there is only a small population left.
Description of the Cozumel Thrasher
The Cozumel Thrasher is a medium sized bird, a little smaller than a robin. It has a chestnut brown back and a white breast with prominent dark streaks. Two white wing bars and a black beak that curves downward also characterize the species.
Like other mockingbirds, T. guttatum spends much of its time on the ground, foraging for insects with its long beak, and it probably also eats wild fruit when ripe berries are available. Its habitat is both deciduous forest and the dense growth near the forest edge. The Cozumel Thrasher is difficult to spot against a background of fallen leaves and many of those reporting sightings describe a secretive bird that can depart and arrive silently and stealthily. When surprised, a Cozumel Thrasher will prefer to run rather than take flight—they can run very fast.
In keeping with the bird's shy ways, little is known about the Cozumel Thrasher’s nesting habits—most mockingbirds nest on the ground, building nests of twigs and other vegetation in thickets, but some nest in trees.
What happened to the Cozumel Thrasher?
Hurricane Gilbert, which struck Cozumel in 1988, seems to have been a turning point for the Cozumel Thrasher. Though the species must have survived many hurricanes before that, the population began to decline sharply. Clearly the hurricane dealt the species a heavy blow, but it seems likely that other factors were also at work:
- Snakes--boa constrictors were introduced to Cozumel Island in 1971, apparently deliberately released after they had been used in the production of a motion picture. Absent before this time, boa constrictors multiplied and no doubt preyed on Cozumel Thrashers both on the ground and in the trees.
- Human development—habitat loss due to land clearing and construction projects has impacted the bird’s habitat, although a lot of suitable habitat still remains.
- Disease—increased human activity and the introduction of non-native species may have brought diseases that the birds are susceptible to.
The last definitive sighting of a Cozumel Thrasher was in 1995 shortly before the arrival of yet another hurricane: Hurricane Roxanne. Since then, there have been sighting reports in 1998, 2001, 2003 and 2004, some by credible sources; however, the 1995 report remains the most recent that is completely unquestioned. Toxostoma guttatum is considered Mexico’s most threatened bird and the species is listed as critically endangered on the IUCN Red List.
Is the Cozumel Thrasher extinct? The species may still exist, secretively surviving in the dense scrubby vegetation and deciduous forests of Cozumel. Recently, BirdLife International named the species in a list of birds to be saved from extinction—one of their first tasks is to confirm its continued existence.
Related content:
More about BirdLife’s plan to save critically endangered bird species.
The Bermuda Petrel is also threatened by hurricanes.
The Kakapo is recovering from near extinction.
Sources:
BirdLife International (2007) Species factsheet: Toxostoma guttatum. BirdLife International
Firefly Encyclopedia of Birds. Perrins, Christopher ed. Buffalo: Firefly Books, 2003
The Endemic Thrasher of Cozumel Island. American Bird Conservancy
