Red Crossbill
Red Crossbills occur in the southern taiga from southern Alaska to Newfoundland south into parts of New England, the Adirondack region of New York, and in the montane conifer forests of the western United States. The range also extends south through the Rocky Mountains into Mexico and Central America. Somewhat isolated populations exist in western Washington and Oregon, northern California, and in parts of the Appalachian Mountains of Virginia and North Carolina. The species also occurs in Europe, Asia, and northern Africa.
Red Crossbill Range Map

Like the similar White-winged Crossbill (L. leucoptera), Red Crossbills breed when food is abundant, and they can breed in almost any month of the year when they find a mature crop of the appropriate species of conifer. Multiple broods are often produced when a particularly abundant food source is found. Breeding typically ceases at the autumn equinox and may resume after the annual molt, which occurs in December or January. In summer, incubation typically begins after the entire clutch is laid; in cold weather, the female begins incubating immediately after laying the first egg. Hatchlings are able to withstand repeated coolings and episodes of torpor, and cold weather development may be slow, especially when food is scarce. Individuals in juvenal plumage might be seen in all months except January and February, and traveling family parties may include juveniles that are still being fed by the parents. Red Crossbills are highly nomadic conifer seed specialists that may irrupt out of their home range when food is scarce. When this occurs, these crossbills may breed in areas far south of their normal range. The extent of the irruptions depends on a combination of population levels and the availability of food. There is no true migration for these birds.

Recent research indicates that there are eight discrete groups of Red Crossbills in North America, each with a distinct call type and morphological adaptations (bill and body size) for feeding on a specific species of conifer. These groups appear to be reproductively isolated, although this is as yet unproven, and have been considered by some to be separate species. There is considerable overlap in size and bill characteristics among the eight groups, so they are not readily distinguishable, except by call. With experience, some call types are distinguishable by ear, but, in other cases, spectrographic analysis of the call may be necessary to determine the group to which a bird belongs.

Red Crossbills eat a variety of foods, including insects and the buds and seeds of many shrubs and trees, but when resources are limited, each type of Red Crossbill favors a particular key conifer species. The cones of different conifer species differ in the depth, thickness, and rigidity of the scales covering the seeds. It is thought that each of the eight types has a bill that is especially adapted to opening the cones of their own key tree species and that differences in call type maintain reproductive isolation. In general, small-billed Red Crossbills favor spruces and large-billed Red Crossbills favor pines.

Very little genetic variation has been found among the eight types, but they do strongly tend to form flocks of a single call type and to mate only within the group, even when two different types are breeding in the same locality. Six of the call types inhabit the Pacific Northwest, five inhabit California and Arizona, and three occur in most of the Rocky Mountains and in the Northeast. Two are found in the Appalachians, and only one type has been recorded in Newfoundland. The Newfoundland type is now rare and possibly extinct.


Visit Shaw Creek Bird Supply and see our selection of Bird Houses, Bird Feeders, Hummingbird Feeders & Heated Bird Baths .

Copyright © 2003 Shaw Creek Bird Supply