Red Crossbill (Loxia curvirostra)

[order] PASSERIFORMES | [family] Fringillidae | [latin] Loxia curvirostra | [UK] Red Crossbill | [FR] Bec-croise des sapins | [DE] Fichten-Kreuzschnabel | [ES] Piquitureto Comun | [NL] Kruisbek

Subspecies

Physical charateristics

Large, powerful, somewhat clumsy and noisy finch, with heavy, crossed bill and sharply forked tail, epitome of genus. Male basically orange to red, with dusky wings and tail. Female and immatures grey or olive, juveniles heavily streaked. Plumage shows few features except for paler rump and vent in adult.
Flight strong and bounding, accompanied by distinctive bursts of loud disyllabic calls. Feeds and moves somewhat like small parrot.
Sexes dissimilar, no seasonal variation.

Listen to the sound of Red Crossbill

[audio:http://www.aviflevoland.nl/sounddb/R/Red Crossbill.mp3]

Copyright remark: Most sounds derived from xeno-canto

Range

Eurasia, Oriental Region, North America, Middle America : widespread

Habitat

In west Palearctic occurs mainly in boreal and subarctic coniferous forests, but also well represented, often by distinct races, in temperate and Mediterranean insular and mountains areas. Extralimitally in Asia ascends to 4500 m, extending to tropical pinewoods.
Ecologically divided largely into pine dwelling populations in more southerly parts of range and spruce-based populations in more northerly, latter being more commonly subject to eruptive movements, during which they may remain to breed, temporarily or for longer, in hitherto unoccupied areas, especially where mature conifer plantations or shelterbelts have recently been developed

Reproduction

The breeding cycle of Red Crossbills is more closely tied to food availability than it is to season. They can breed at almost any time of year, and will do so even in mid-winter if there is an abundant source of seeds. They are monogamous, and pairs form within flocks. The female builds the nest, which is located on a horizontal branch high up in a conifer tree. The nest is a bulky cup of loose twigs, grass, and bark strips, lined with fine grass, lichen, feathers, and hair. The female typically incubates 3 eggs for 12 to 16 days. The male brings food to the incubating female and to the young for the first few days after they hatch. After five days of continuous brooding, the female joins the male in bringing food to the young. The young leave the nest after 18 to 22 days. The parents continue to feed the young for about a month after they hatch. The bills of young birds are not crossed at hatching, but cross as they grow. By 45 days they are crossed enough for the young to extract seeds from cones.

Feeding habits

Conifer seeds, generally spruce, but in some parts of range (e.g. England and Mediterranean region) mostly pine. Very agile and acrobatic forager, easily fluttering from twig to twig, sidling along branches, hanging from cones, and clambering around, often using bill as help like parrot; either works at cones, usually riper ones, extracting seeds in situ while hanging on cone, or snips them off (sometimes taking whole sections of twig) to carry to perch, often in fork, where held under foot and seeds removed. Often flies to perch carrying cone as heavy as bird itself; quite able to hold loose cone against underside of branch and extract seeds while upside-down; legs and toes are adapted for grasping and securing cones, as bill is for extracting seeds. Inserts bill-tips between scales of cone from side, moves lower mandible (which is more angled than upper) sideways, flat against top scale, causing tip of upper mandible to push bottom scale downwards, then scoops out seed with tongue; on thin-scaled cones, upper mandible can be used to hook seeds out. If seed is still fast, can open scales further by inserting closed bill and turning. Away from conifers, readily feeds in broad-leaved trees, taking buds as well as fruits and insects, particularly caterpillars and aphids.

Conservation

This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be stable, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is extremely large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
Loxia curvirostra is a widespread resident across much of northern Europe, and also
occurs more patchily farther south, with Europe accounting for less than a quarter
of its global range. Its European breeding population is very large (>5,800,000 pairs),
and was broadly stable between 1970-1990. Although there were widespread
fluctuations during 1990-2000, the vast majority of national populations-including
key ones in Russia and Fennoscandia-were broadly stable.
Red Crossbills are usually found in small flocks year round. They typically climb in mature conifers, using their bills to grab branches and cones. They will also occasionally land on deciduous trees and forage for aphids. Their bills are adapted for removing seeds from cones, and they start at the bottom of a cone and spiral upward, prying open each scale and removing the seeds with their tongues. The bills can cross in either direction, and the direction of the cross dictates the direction that the bird spirals up the cone. Each type has a distinct flight call, which is helpful in identification and may play a role in maintaining the isolation of each group

Migration

Resident and dispersive, also irruptive. In most years, birds disperse short distances in midsummer to find new feeding areas, moving in flocks in various directions but remaining within regular range. Local numbers may therefore fluctuate greatly from year to year, dependent on varying state of conifer seed-crops, especially spruce; timing of movement coincides with formation of new spruce cones. In irruption years (mostly involving L. c. curvirostra), birds move much further (up to 4000 km), mainly in one direction; such movements vary considerably in extent and duration, and tend to begin earlier and end later than in normal years. Irruptions probably result from high population levels coinciding with poor or moderate seed harvests; early departures suggest that crowding may sometimes alone stimulate movement. Birds frequently stay to breed in invasion areas, reinforcing local populations or colonising new sites; these settlements usually temporary, but occasionally permanent, e.g. colony in East Anglia (eastern England) dates from 1909 invasion.

Distribution map