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David Sibley

You too can record and identify Crossbill call types

If you’ve followed any of the discussions about identifying Red Crossbill call types, you may have given up on taking an active role in crossbill study, thinking that it would require thousands of dollars worth of recording equipment and computer software. Well, that is simply wrong. Most people can enter the field and start identifying crossbills

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Bill size, not shape, distinguishes Cackling and Canada Goose

I recently checked the bill length to bill depth ratios of Cackling and Canada Geese, expecting to find a consistent and useful difference. The bills of Cackling Geese are often described as “stubby” and I was always under the impression that they were short and relatively deep. Working with the measurements in Pyle (2008, Identification

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Wing twisting explained

In discussing the identification of the woodpecker in the Luneau video, my colleagues and I suggested that the extensive white visible in the wings could be accounted for, in part, by the natural twisting of the wings during flight. A bird flying away would show the underside of the wings during the entire downstroke. In the

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