Common Redpolls are always a special, finch-y treat in the winter in the Cities. This year I haven't seen many, and had to head to Sax Zim for my fix. Cornell Lab of Ornithology has this to say about their seasonal movement,"During the summer, Common Redpolls are found in boreal and taiga regions of both the Old and New World Arctic, where they are often among the most common breeding passerines. In North America, their distribution shows significant overlap with human populations only in winter, and then only in alternating irruption years. The irruption cycle displayed by this species is driven by widespread failure in seed-crop production among high-latitude tree species—especially spruce (Picea sp.) and birch (Betula sp.)—which forces these birds to winter farther south.)
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