About the Cassin's Finch
The attractive Cassin’s finch of the montane west is slightly larger and longer winged than the similar purple finch, which it occasionally overlaps with during winter. It is often seen in small flocks, mainly in pine forest, but it is known to occasionally invade into lowland deciduous areas during the winter. It occasionally joins the more common house finch at seed feeders in winter. Polytypic. Length 6.3".
Highly sexually dimorphic with males pink and females brown. Generally lighter pink than other Haemorhous finches, with distinctive fine streaking on the undertail coverts. Male: a bright pinkish-red crown contrasts sharply with a brown streaked nape. The back is heavily streaked and washed pink. The fairly wide eyebrow and submoustachial stripe are both pale pink. The light pink throat and breast blends into the white on the lower belly. Varying amounts of fine black streaking cover the flanks and undertail coverts. The bill is longer and more pointed than other Haemorhous finches. Female: the upperparts are brown and streaked, while the underparts are white with fine, crisp streaking, which is heaviest on the breast and flanks. The undertail coverts are also finely streaked. The rather diffuse face pattern has a noticeably pale eyebrow and submoustachial stripe.
Two described subspecies show subtle plumage and size differences, with birds of the Sierra Nevada and Cascades slightly darker and with longer bills than those of the Rocky Mountains.
The male is most similar to the male purple finch, but there is only limited overlap in range during the breeding season. The Cassin’s eyebrow and streaking on back tend to be wider and frostier; it usually has fine streaking on the flanks and undertail coverts as well. The primary projection is noticeably longer in the Cassin’s, as is the bill. Note the different flight calls between the 2. Distinguishing a female Cassin’s from a female purple can be more of a challenge. The Cassin’s and house overlap more, with the Cassin’s typically found in coniferous forest and the House in the lowlands, but they might overlap in winter when Cassin’s populations irrupt to the lowlands. Note the Cassin’s pink eyebrow, finer black streaking on the flanks, frostier upperparts, longer primary projection, and longer bill with a straight culmen.
Call: in flight gives a dry kee-up or tee-dee-yip. Song: a lively, varying warble, longer and more complex than the purple or house finches’.
Status and Distribution
Fairly common in montane coniferous forests. Breeding: found throughout much of the Rocky Mountains, west into the Cascades in Washington and Oregon, and the Sierra Nevada and southern mountain ranges in California. Winter: unpredictable. Often stays in breeding range, but periodically drops to lower elevations. Winters as far south as the mountains of central Mexico. More common in the lowlands of the interior west than is purple finch. Vagrant: casual to eastern Colorado, Nebraska, and Kansas; northern Texas; Alaska; and California coast.
—From the National Geographic book Complete Birds of North America, 2006