The small, heavily streaked Pine Siskin is often irruptive in winter, and can be seen over large parts of the U.S. where it comes to bird feeders, especially for thistle seed. Some of these traveling Pine Siskins can remain to breed, even in areas far from the normal breeding range of the species.

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Photograph © Glenn Bartley.

Pine Siskins usually breed in small colonies, although each pair still defends a small area around their nest. Most of their breeding range is outside that of the Brown-headed Cowbird, so there is little opportunity for nest parasitism, although where the two species do overlap, significant parasitism has been observed. Siskins usually abandon cowbird chicks before they fledge.