I often am amazed by just how many bleeding animals there are in the world, and despite my lifelong dedication to finding out about them, I can be totally astounded by something. I came across this week's animal of the week, appropriately enough, through Twitter: last week @BirdLife_News posed the question what's the smallest flightless bird (one extant/one extinct)?
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| Inaccessible Island rail: Brian Gratwicke |
Now, the extinct one I knew, it's the Stephen's island wren, a tiny dot of a bird endemic to an island between the two large islands of New Zealand the last of which was killed by the lighthouse keeper's cat. That's one of the classic stories of extinction, one I'd heard and told many times before. But the living one was completely new to me: the Inaccessible Island rail. Not only did I not know there was an island called Inaccessible Island (part of the Tristan archipelago in the southern Atlantic, but also, I didn't know that living on it was the 17 cm, 30 g flightless relative of coots, moorhens, and the like*. Now rails are one of the most widespread groups of birds with species, some flightless, settled on islands around the globe.
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| Tristan thrush: Brian Gratwicke |
But it's not even the Inaccessible Island rail that's this week's animal. A quick google led me on a bit of a wikipedia trail. The rail has been able to miniaturise and lose the power of flight owing to the dearth of predators on inaccessible island. But nature abhors a vacuum, and eventually something will fill a vacant niche. And here we meet this week's actual animal,
Nesicichla eremita (Tristan thrush; really it should be
Turdus eremita, I am picky). While it's mainland relatives are usually happy eating berries and insects with the occasional snail or worm thrown in, the Tristan thrush has developed a taste for seabirds, eggs, and chicks. Across the archipelago, the Tristan thrush raids the nests of petrels, rails, and even albatrosses (their eggs, not like a whole one); the thrushes have even evolved a brush like structure on their tongues to help them extract the filling of delicious seabird eggs.
Like the
vampire ground finch of Wolf Island in the Galapagos, the Tristan thrush is another great example of how life on an island can lead to unexpected behaviour among unassuming looking creatures. Of course, if there was just a pharmacy on Inaccessible Island, the rails could get themselves a tube of canesten to rid themselves of their problem thrush.
*I used to really like coots, moorhens, crakes and gallinules, but not so much anymore. I've gone off the rails.
