Rails on the Ropes--From Today's Lesson in one of my Classes

Rails are small quail- or chicken-like birds evolved primarily for stealthy stalking on muddy sediments in grassy wetlands. They have sharp bills and sharper eyes that can spot movement of the small invertebrates—amphipods, crabs, insects—that are their preferred food from meters away. It takes just a moment for them to be in position to pluck the meal from silt or stem.

Above is an image of a clapper rail, a rather typical species that lives in North American coastal marshes [slurped from the web, credited to the New York Public Library, I believe].

Most rails look hopeless in flight. They vastly prefer to run, but if pressed they clatter up out of the grass, thrashing noisily at the air, make headway for a few meters, and drop gratefully back to the mud to dash away. Despite their inefficient aerial skills, many species make long migrations. One can only speculate that they are exhausted at the end of the trip and need to bulk up on extra helpings of seafood to recover.

Many bird species, when they reach new habitat where large, active predators are absent or rare, lose the power of flight. Rails seem to do so with particular aplomb. As rails populated successive islands and atolls across the Pacific where the only predatory threat was the occasional overflight by a frigatebird, they settled in, became flightless, and went to work gobbling shrimp and fiddler crabs.

Flightlessness has its drawbacks. If conditions change—i.e., predators suddenly show up—you may be in trouble. Poster child, of course, is the Mauritius dodo [Raphus cucullatus], large, flightless, and clumsy. Its flesh was tough and didn’t taste very good, and wasn’t favored for ship’s provisions. However, between the occasional sailor’s meal [perhaps when they couldn’t hunt down more edible components of the avifauna] and the rats, cats and pigs that showed up with the vessels, it only took a few decades to go extinct [the Wikipedia entry is complete and well-referenced, see http://en.wikipedia.org/wiki/Dodo ].

The Laysan Rail [Porzanula palmeri] was native to its namesake island and one or two associated atolls in the northern Hawaiian islands. Discovered [by westerners] and described in the late 1800s, it went extinct on Laysan a few decades later after rabbits liberated by the guano diggers who lived on-island decimated the vegetation the birds depended on for shade and cover.

Laysan Rail. Also slurped from the web. 

However. In a move anticipating modern methods of threatened species management, a colony of Laysan Rails had been established on Midway Island, another on nearby Pearl and Hermes Reef. The latter was decimated by a series of typhoons in the 1930s. That left the Midway population, by all accounts thriving, as the basis for the future of the species.

Bummer. By the time the runways were constructed and fought over and combat finally ended, the Laysan Rail was gone. Likely no single factor took the last survivors. Rats, cats, habitat destruction, possibly the occasional cantonment meal. There was a lot of pressure on the little guys. There was hope well into the 20^th century that there might be remnant populations, if not on Midway, then elsewhere in the leeward Hawaiian Islands. I believe that hope is mostly dissipated, and the Laysan Rail has taken its place with the dodo as a cautionary tale for those of us concerned with biodiversity in the 21^st century.


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