Monday, January 23, 2012

Common Redpoll

Common Redpolls appeared at our Dundas banding site on the first of January, but did show themselves to me until this cold, icy, snowy Monday. Redpolls are irruptive, winter finches. They breed in the high arctic, both above and below the treeline.

Although Knox and Lowther (2000) write that redpolls invade every other year, I found their presence not to be predictable in northeastern South Dakota. The most I ever banded in one year was 2179 in 1994. During my 26 years of Dakota banding (1979-2004) there were five years when I did not band a single redpoll. I did, however, band at least one redpoll in 21 of those years. I banded over 1000 individuals only in three years (1982, 1992, and 1994). The average number of redpolls banded per year was 198, but the standard deviation was 379!

In Northfield, I've banded Common Redpolls only in 2009. According to Knox and Lowther, the irruption cycles are caused by spruce and birch seed crop failures, which force the redpolls to winter further south during the lean-seed years. The redpoll in the photograph above is from Aberdeen, South Dakota. Bright red birds can be identified as second-year males. Females and first-year males can not be told apart by plumage.

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