The red crossbill (Loxia curvirostra) is a small passerine bird in the finch family Fringillidae, also known as the common crossbill in Eurasia. Crossbills have distinctive mandibles, crossed at the tips, which enable them to extract seeds from conifer cones and other fruits.
Adults are often brightly coloured, with red or orange males and green or yellow females, but there is wide variation in colour, beak size and shape, and call types, leading to different classifications of variants, some of which have been named as subspecies.
Crossbills are characterized by the mandibles crossing at their tips, which gives the group its English name. Using their crossed mandibles for leverage, crossbills are able to efficiently separate the scales of conifer cones and extract the seeds on which they feed. Adult males tend to be red or orange in colour, and females green or yellow, but there is much variation.
In North America, nine distinct red crossbill variants (referred to as call types) differing in vocalizations as well as beak size and shape are recognized. Each call type evolved to specialize on different species of conifer.
The red crossbill breeds in the spruce forests of North America, as well as Europe and Asia. Some populations breed in pine forests in certain areas of all three continents, and in North America, also in Douglas-fir. It nests in conifers, laying 3–5 eggs.
This crossbill is mainly resident, but often irrupts south when its food source fails. These irruptions led in the twentieth century to the establishment of permanent breeding colonies in England, and more recently in Ireland. This species forms flocks outside the breeding season, often mixed with other crossbills.
The first known irruption, recorded in England by the chronicler Matthew Paris, was in 1254; the next, also in England, appears to have been in 1593 (by which time the earlier irruption had apparently been entirely forgotten, since the crossbills were described as "unknown" in England). The engraver Thomas Bewick wrote that "It sometimes is met with in great numbers in this country, but its visits are not regular", adding that many hundreds arrived in 1821. Bewick then cites Matthew Paris as writing "In 1254, in the fruit season, certain wonderful birds, which had never before been seen in England, appeared, chiefly in the orchards. They were a little bigger than Larks, and eat the pippins of the apples [pomorum grana] but no other part of them... They had the parts of the beak crossed [cancellatas] by which they divided the apples as with a forceps or knife. The parts of the apples which they left were as if they had been infected with poison." Bewick further records an account by Sir Roger Twysden for the Additions to the Additamenta of Matt. Paris "that in the apple season of 1593, an immense multitude of unknown birds came into England ... swallowing nothing but the pippins, [granella ipsa sive acinos] and for the purpose of dividing the apple, their beaks were admirably adapted by nature, for they turn back, and strike one point upon the other, so as to show ... the transverse sickles, one turned past the other.
Photos and videos Troodos by George Konstantinou