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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. |
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Adult
males 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. Few ornithologists
seem inclined to give these forms species status at present. |
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