A Mule and its Anis

 

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From southern Mexico to northern South America, one of the first birds a birder new to this part of the world will check off is almost invariably the Groove-billed Ani (Crotophaga sulcirostris).  Common in the kinds of disturbed environments nearly every visitor passes through and moving relatively slowly but noisily about in groups close to the ground, they’re hard to overlook.

Groove-billed anis have also been the focus of scientific research.  The famous Costa Rican naturalist and ornithologist Alexander Skutch first explored their natural history while groundbreaking behavioral biologist Sandra Lee Vehrencamp detailed their fascinating communal breeding system.  Others too have studied these birds.

The relative ease with which we can observe the birds and the fact that some very good researchers have done just that would suggest that we would have a solid handle on the basic natural history of these birds.  But there is one aspect of these birds’ behavior that’s been somewhat of a mystery.  Interestingly, it’s probably a mystery that countless campesinos could have answered for us had they wherewithal and any idea that anyone cared!

We have long known that Groove-billed Anis associate with cattle, horses, and mules. What hasn’t been clear are the forms this association takes.  We know that, like cattle egrets, Groove-billed anis occasionally follow large domestic mammals and catch the insects these animals scare out of hiding while wandering about.  Bent (1940) claimed, however, that Groove-billed Anis not only did this but also perched on cattle and even sometimes removed ticks.  Alexander Skutch, however, doubted that the birds did this. He suggested that people who thought they had seen this had confused anis with Giant Cowbirds, a similar-looking species well known for this kind of behavior.

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