Friday, February 6, 2009
A rail jumps the track
On a bitterly cold day exactly three years ago, a resident of nearby Apsley discovered this unfamiliar bird on the street, beneath a discarded Christmas tree. It had a damaged leg, was unable to fly, and was thin as a rail. A few calls were made and the bird was driven to the Toronto Wildlife Centre for assessment. It was identified as an immature Purple Gallinule.
This pigeon-sized marsh bird is common in the tropics and subtropics. In the U.S. it breeds in wetlands along the coastal plain of the Gulf of Mexico with spotty records extending up the Mississippi watershed as far north as Illinois. There have been a few summer sightings in southernmost Ontario but these birds are thought to be individuals that overachieved on their northward migration. A winter occurrence is very unusual.
Unfortunately, the leg injury proved to be very serious and the bird was eventually euthanized. The story is both sad and illustrative.
Some authors describe rails, including crakes, coots, moorhens and gallinules, as very weak flyers and there's nothing in my personal experience to suggest otherwise. I have seen very few rails (other than coots) on the wing. Most often I've heard them and once or twice each summer I'll glimpse a Sora or a Virginia Rail skulking among the cattails. In the hand, they seem lean and bony. They certainly don't have the obvious broad pectoral muscle mass required for explosive vertical takeoffs that we see in Ruffed Grouse.
Yet grouse seem to stay very close to home and rails of many species seem not to have realized that they are weak flyers. Vagrant Purple Gallinules have shown up in Quebec, New Brunswick, Nova Scotia, Labrador and Newfoundland. Others touched down in Iceland, Norway, the Azores and South Africa. There's even a record from the Galapagos (West and Hess, 2002). Several other rail species have a histories of straying across continents and hemispheres. They may not be the best navigators but they seem to be perfectly competent flyers.
One result of all of this poor navigation is a remarkable global distribution that includes Africa, Australia, Eurasia and the Americas. Many oceanic islands have been colonized. Where such islands lack predators, natural selection seems to have favoured those descendants that allocated energy into more earthbound pursuits. The flightless Laysan Rail (Porzana palmeri) was one of many such examples. The progenitor of this species is the Old World Baillon's Crake (Porzana pusilla), a number of which made landfall on Laysan (at the north end of the Hawaiian Island chain) after it was exposed by falling sea levels about 125,000 years ago. The loss of flight occurred in a mere blink in evolutionary time (Olson 1999).
[Alas, it only takes a few years for introduced predators - rats, cats, mongoose, snakes and humans - to wipe out these flightless insular species. The last Laysan Rail died in the mid-1940's. Since 1600, 20 insular rail taxa (of which 18 were flightless) have become extinct]
Our Purple Gallinule should have been wintering in a subtropical wetland in the company of ibises, anhingas and egrets, perhaps in the Caribbean. In finding itself in the coldest depths of an Ontario winter it sealed its fate and demonstrated a familial trait - that of straying - which has allowed the rails to successfully colonize far-flung continents and scores of oceanic islands.
Sources and photo credits:
Olson, S. L. 1999. Laysan Rail (Porzana palmeri), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/426a.
West, R. L. and G. K. Hess. 2002. Purple Gallinule (Porphyrio martinica), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/626.
Photos of injured Purple Gallinule courtesy of Kim Valenta of the Toronto Wildlife Centre.
Photo of Purple Gallinule on lily pad in Melaque (Jalisco, Mexico) courtesy of Howard Platt.
Range map linked from the Cornell Laboratory of Ornithology.
Related and recent:
A nice series of Purple Gallinule images taken in Guatemala City by Mike at 10,000 Birds.
Rail images from Lake Titicaca by Paul at The Lost Frenchman Blog.