29-1-2021 MONTE CORONA, VALENCIA - RED CROSSBILL (FEMALE) (Loxia curvirostra)

The red crossbill or common crossbill (Loxia curvirostra) is a small passerine bird in the finch family Fringillidae. 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 beak size and shape, and call types, leading to different classifications of variants, some of which have been named as subspecies. The species is known as "red crossbill" in North America and "common crossbill" in Europe.

Crossbills are distinguished 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; juveniles are greyish-green and streaked.

The distinctive crossed mandibles eliminate most other species, but this feature is shared by the similar two-barred crossbill, with which it overlaps considerably in range. The two-barred crossbill has two bright white wing bars, while the wings of the red crossbill are entirely brownish-black.

The red crossbill is the only dark-winged crossbill throughout most of its range, but it overlaps at least seasonally with the small ranges of the very similar parrot, Scottish, and Cassia crossbills. These species were formerly considered subspecies of the red crossbill, and though they show very slight differences in bill size and shape, they are very difficult to visually distinguish from the red crossbill and are generally best identified by call. The plumage differences between these four crossbills are negligible, there being more variation between individual birds than between species.

Length: 20 cm

Weight: 40–53 g

Wingspan: 27–29 cm

Red crossbills breed in a variety of coniferous forests across North America and Eurasia. Its movements and occurrence are linked very closely to the availability of conifer seeds, its primary food source. They typically nest in late summer (June–September) when the seeds of most conifer species mature, but may nest at any time of year if they locate an area with a suitable cone crop.

This species is considered nomadic and highly irruptive, as conifer seed production may vary considerably year to year and birds disperse widely to breed and forage when the cone crop in their particular vicinity fails. In many areas of their range they are considered irregular because they may be present in certain years and not in others. The various types of red crossbill (see Taxonomy and Systematics) prefer different types of conifers, and therefore may differ in the regularity, timing, and direction of their irruptions. A few populations, such as the Newfoundland crossbill (North American type 8), are resident and do not undertake significant movements. When they are not breeding, the various types of red crossbill may flock together, and may also flock with other species of crossbill.