Red Crossbill
Loxia curvirostra

Migratory Status: Short-distance migrant

PIF Population Estimate: 6 000 000

Percent of western hemisphere population breeding in boreal forest: <25%

BAM Effective Detection Radius (m) : 76.59

PIF Maximum Detection Distance (m) : 125

Canadian BBS Population trend: -1.7 n.s. (-3.5 to 0.1)

Life History

The Red Crossbill is a medium-sized finch with noticeably crossed mandibles. The body colour of adult males varies from brick red to reddish green, and the tail and wings are blackish brown. Females are more uniform in colour, generally olive to gray, with a greenish tinge on the breast and rump. The Red Crossbill is widely distributed in the northern hemisphere, occurring wherever there are large tracts of coniferous forest. Some populations are relatively sedentary, while those in boreal regions are highly nomadic. Migrations occur one to three times each year, depending on the availability of food resources.

Red Crossbills live almost exclusively in coniferous forests. North American populations have diverged and have become specialized in foraging on different cone species, with corresponding variation in bill size and shape. Those with the smallest bills prefer hemlock (Tsuga spp.) seeds, while the large-billed varieties concentrate on large pine (Pinus spp.) cones. These populations may actually represent distinct species.

To extract a seed, Red Crossbills force the cone scales apart until the tongue can lift the exposed seeds out. Then, to remove the seed, the tongue pushes it against a specialized husking groove on the lower mandible. Small items are swallowed whole, but larger ones are crushed before ingesting. In summer, Red Crossbills will feed on insects, and will eat non-conifer seeds when they are abundant or when cone crops are poor.

Red Crossbills are not particularly territorial; breeding males will sing in close proximity to each other. Foraging birds will feed on adjacent cones with little or no antagonistic interaction. Both sexes sing, but the female does so sparingly and is quieter than the male. The song is given from a treetop perch, near the nest or in flight. It is a series of both sharp and buzzy notes, sometimes described as “pit-pit, tor-r-ree, tor-r-ree”. The typical flight call is a “chip-chip-chip”. The quality of the call differs among Red Crossbill populations. Where two or more populations co-exist, they rarely form mixed flocks.

Reference(s)

Adkisson, C. S. 1996. Red Crossbill (Loxia curvirostra), The Birds of North America Online, . A. Poole, Ed. Ithaca: Cornell Laboratory of Ornithology; Retrieved from The Birds of North America Online database: http://bna.birds.cornell.edu/bna/species/256