The Common Crossbill
(Loxia curvirostra) is a small passerine bird in the finch family
Fringillidae. It breeds in the spruce forests of North America,
where it is known as Red Crossbill, Europe and Asia; some populations
(different species?) 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 will regularly erupts south if its food source fails.
This species will form flocks outside the breeding season, often
mixed with other crossbills. The
crossbills are characterised by the mandibles crossing at their
tips, which gives the group its English name. They are specialist
feeders on conifer cones, particularly the various spruce species
but also some populations (different species?) in douglas-fir
and various pine species, and the unusual bill shape is an adaptation
to assist the extraction of the seeds from the cone.
tend to be red or orange in colour, and females green or yellow,
but there is much variation. This species is difficult to separate
from Parrot Crossbill and Scottish Crossbill, both of which breed
within its Eurasian range. The identification problem is less
severe in North America, where only Red Crossbill and White-winged
Crossbill occur. Plumage distinctions from Parrot and Scottish
Crossbills are negligible. The head and bill are smaller than
in either of the other species. Care is needed to identify this
species. The glip or chup call is probably the best indicator.
Work on vocalisation in North America suggest that, in that continent
alone, there are eight or nine populations of Red Crossbill with
different calls, which rarely if ever interbreed. These forms
also vary in terms of bill size and structure, and specialise
on the seed cones of different species of conifer.
Above Images Come From The U.S. Fish and Wildlife Service