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Saturday Bird Blogging: the Patagonia Effect

ALBUQUERQUE, N.M. — Matt over at Albuquerque Birding has a post on the grand convergence of rare birds in the Albuquerque bosque over the last month: rusty blackbirds, winter wrens and Pacific wrens south of the Central Avenue bridge, and Thayer’s gulls up by Alameda.

It’s an example of what birders have dubbed the Patagonia Picnic Table Effect, after an incident at a picnic area in Arizona. One rare bird shows up, a mob with binoculars descends, and more rare birds are found. My question – are there always lots of rare birds around, and it just takes a bunch of birders flooding the zone to find them? Matt’s helpful answer, down in the comments on his blog:

The chances of finding other birds always goes up if more people are looking, and rarer species will be found with more effort. It’s kind of like ecological sampling–you’ll get the most common taxa first and eventually come across less abundant ones. I wouldn’t say that just any random patch might immediately produce rare birds if more birders look, but in good habitat and at the right time of year something rare might be around if someone could only find it. The Rio Grande valley is a major migrant route and all sorts of rare birds show up at the migrant traps in Sierra County where the bosque is limited to small patches. Those same birds must move through the Albuquerque area, but the habitat is more spread out and they are harder to find.

I’ve been out with friends to see the rusties and found the Pacific wren on a solo trip. I’ve seen what I assume are the Thayer’s gulls, though I wasn’t close enough for a positive ID (and Matt’s explanation of the identification problem there suggests caution). But beyond adding birds to the life list, the hunt guarantees a lovely day in the bosque.


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