Aug 6, 2012

connecting the rails

Several recent sightings in Costa Rica have firmed up the likelihood that clapper rails are residents in mangrove swamps along the Pacific coast. First documented in 1998, the birds are now being seen often enough to make residency likely, as opposed to clapper rails being transients or stray birds. The country's ornithological union has just added the rail to its list of residents.

It is always good to add new territory for birds that have lost as much habitat as rails, prime victims of our centuries-old tendency to drain or fill wetlands. The clapper rail's preference for saltwater has shielded it from development compared to smaller cousins like Virginia rail and yellow rail, who use what is left of eastern, interior marshes as breeding grounds. Still, the clapper rail is not immune. Gulf coast mangroves and Atlantic coast salt marshes have all shrunk as we have encroached. The San Francisco Bay population of clapper rail is considered endangered because so little of its habitat remains.

Clapper rails are found throughout the Americas, and there are multiple described subspecies that vary in size and coloration. With so little known about them, it is unclear which subspecies the Costa Rican rails might be.

When you get right down to it, we do not know enough about rails to say for sure whether what we call Rallus longirostris is one species or two or more. We are not sure how much they wander for food or mates or how likely they are to fly inland to cross from one coast to another.

Costa Rican birds could be part of a Baja population or part of an Ecuadoran population, or Gulf coast birds that crossed the Central American isthmus to establish a population on the Pacific coast. Connecting Costa Rica with the Baja population is tempting, but Costa Rican birds have little red in their breast feathers. Baja birds have the reddest breasts of any clapper rail variant.

Costa Rica is an intriguing new dot in an empty area of the clapper rail range map.

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