The Pine Siskin is another irruptive bird species like the Red-breasted Nuthatch.  This siskin was in a small group of siskins in vegetation along the Merrimack River near the New Balance factory.

Pine Siskins are distributed across much of Canada and at higher elevations in the western portions of the United States. Periodically, they will irrupt into parts of the East and into areas of lower elevations in the West.  It is hypothesized that these irruptions occur due to variations in the bird’s food supply on their wintering grounds. When Pine Siskins irrupt into the southern ranges of the map above, food abundance in their typical wintering grounds may be low. You can read a very interesting report on the “Biennial Irruptions of Pine Siskins Across North America” at the Audubon website.

Here is the link:  http://birds.audubon.org/what-were-learning-christmas-bird-count-biennial-irruptions-pine-siskins-across-north-america

3 Photos posted:  http://www.pbase.com/birdshots/image/146967503