Pine Siskin, Hillsboro, Oregon on 4 March 2010 by Greg Gillson.If you feature a thistle feeder with Niger seeds at your bird feeding station, you will likely get flocks of Pine Siskins occasionally, often in winter and spring. Highly, nomadic, their movements and numbers are unpredictable at any time of year.
Pine Siskins are superficially similar in coloration to female House Finches, though they are the size and shape of the smaller goldfinches to which they are closely related. Like goldfinches, their bills are small and thin and tails deeply forked. You may note a yellow wing stripe and yellow base to the tail--especially visible in flight (see photo above). The darkness of the plumage and the intensity of yellow is highly variable between individuals.
They nest fairly commonly in conifer forests throughout the mountainous regions of the Pacific Northwest. They can be hard to see high in the canopy, but easily detected by their buzzy rising calls.
In winter they often irrupt into the lowlands, following changing food resources. John Rakestraw has been seeing them recently at his feeder in Portland, Oregon and writes a bit about them on his blog.
Besides small cones of conifers, Pine Siskins also feed in winter upon the cone-like fruit of the deciduous red alder.