Sunday, November 27, 2011

Pine Siskin

On 22 November 2011, a large, mixed flock of Pine Siskins and American Goldfinches descended on our bird feeders. I banded 27 (10 siskins and 17 goldfinches). The siskins were the first of this fall at our home. The next day the flock vanished.

Last December, I wrote about siskins, “ During my 25 years of banding in Aberdeen, South Dakota, I banded 13,239 Pine Siskins,more than any other single species and despite their being absent during somewinters. Some summers, after abundant winters, siskins bred in the area.Two recoveries illustrate their nomadic nature--one banded in Aberdeen on 10March 1985 was found in Connecticut on 11 March 1988; another Aberdeen siskin,banded on 12 December 1992 was recovered near San Francisco, California, on 5January 1995."

What is responsible for the irruptive nature of this species? Presumably regional failures of conifer cone crops and fruiting trees such as aspens cause these irruptions (Dawson 1997). The problem is the difficulty in estimating relative tree seed numbers versus siskin populations.

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