Red Crossbill
(Loxia curvirostra)
Cool fact: 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.

 

Listen to recordings of  Red Crossbill and White-winged Crossbill from the Library of Natural Sounds:

Red Crossbills by Larry McQueen
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.

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.

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.

Description:  Red Crossbills are stocky, large-headed, medium-sized finches with thick conical bills. The mandibles curve toward each other and cross at the tip. The brown wings lack the broad, white wing bars of the similar White-winged Crossbills. The forked tails are also brown. Most males are brick red or orange red, but some variants may be orange or yellowish orange. Males are brightest on the forehead, crown, and rump. The mantle and back are colored like the crown but may be mottled with darker feathers. The underparts are almost entirely red in typical individuals or are yellowish orange in some variants. Undertail coverts are grayish white with darker spots. The legs and feet are dark brown.

Females are generally olive green above and yellowish green below. The forehead, crown, nape and back are mottled with dusky brown. The tail and wings are brown. The throat of most types is gray, or yellowish with gray along the sides.

Juveniles and first-winter birds are paler than adult females with dark stripes. Some may display wing bars, which are thinner (especially the upper wing bar) than those of the White-winged Crossbill, and may have a buffy tinge rather than a pure white color. First-summer males resemble adults, but they show patches of red with yellow or brown feather tips.

Recording credit:
Red Crossbill song recorded by Geoffrey A. Keller.

White-winged Crossbill song recorded by Gregory F. Budney.
White-winged Crossbill call and additional song recorded by William W. H. Gunn.
These recordings appear on the Library of Natural Sounds' production, The Bird Songs of Alaska

Copyrightę 1999 Cornell Laboratory of Ornithology


 

 

 

male Red Crossbill (detail) by Warren Greene slide# 639.1
male Red Crossbill

 

 


female Red Crossbill (detail) by Brian Henry slide# 639.2ytes)
female Red Crossbill

 

 

 

 

 


male White-winged Crossbill (detail) by Warren Greene slide# 640.1
male White-winged Crossbill