[order] Passeriformes | [family] Fringillidae | [latin] Loxia scotica | [UK] Scottish Crossbill | [FR] Beccroisé d’Ecosse | [DE] Schottischer Kreuzschnabel | [ES] Piquituerto escossês | [IT] Crociere scozzese | [NL] Schotse Kruisbek

Schotse Kruisbek determination

copyright: youtube

The Scottish crossbill is a sparrow-sized member of the finch family, measuring about 16 centimetres in length, and is closely related to goldfinches and canaries. Males and females are quite different in colouration, with the male having a bright orange-red, brick-coloured plumage, while the female is a dull green-yellow, which provides her with good camouflage when she is sitting on her nest. Both males and females have dark brown wings and tails.
All crossbills are instantly recognisable by the curved mandibles which cross over when their bills are closed - they are the only type of bird which exhibits this characteristic. The mandibles cross either to the left or the right, and enable the bird to pry open the tight scales of cones and extract the seed from within them. It is the differences in bill sizes between the Scottish crossbill and its close relatives which led to it first being identified as a separate species. The common crossbill, which feeds mainly on spruce seeds contained in relatively small cones, has a slender bill, whereas the parrot crossbill has a much larger bill for opening the tougher cones of Scots pine. The bill of the Scottish crossbill is in between the others in size. The Scottish crossbill is a gregarious species, and is often seen in flocks or groups. This behaviour is thought to have arisen partly as a result of the bird's diet, which consists almost exclusively of the seeds of Scots pine (although this has been augmented more recently by seeds of introduced exotic conifers such as European larch). As the cones of Scots pines take 2 years to ripen and cone production varies considerably from year to year, the birds have to vary their feeding grounds, depending on where the cones are abundant, and flocking may be a natural consequence of them converging on cone-laden trees.
The crossbill uses a variety of different calls and sounds, including a loud piercing cheeping call whilst in flight and a deep toop call to express a range of emotions, such as alarm or aggression.

Scottish crossbills are believed to be largely restricted to the Caledonian pine forests and old Scots Pine plantations of the Scottish Highlands (Knox, in Gibbons et al 1993). They nest mainly in old pine forest, including areas of bog pines, but also locally in Larches and other predominantly coniferous woodland. Scottish Crossbills do not usually nest in dense plantations.

Loxia scotica is endemic to Europe, where it is resident in northern Scotland (United Kingdom). Its breeding population is probably very small (as few as 300 pairs), but trend data were not available for either 1970-1990 or 1990-2000. Consequently, this poorly known species is categorised as Data Deficient.
This bird is endemic to Scotland where it inhabits old Caledonian pine (Pinus sylvestris) forests. Its population is estimated at 300-1300 breeding pairs. It seems to be stable, but it is vulnerable because old forests are gradually replaced by young plantations and native pin by fast growing exotic species.
The Scottish crossbill is endemic to Scotland, and is the only bird which is restricted exclusively to the UK. However, there is some taxonomic uncertainty as to whether it is in fact a species in its own right, or whether it is a variety of one or other of two closely-related species. These are the common or red crossbill (Loxia curvirostra), which is found in coniferous forests in North America, Europe and Asia, and the parrot crossbill (Loxia pytyopsittacus) which occurs throughout Scandinavia and western Russia. All three species are identical in plumage, and the Scottish crossbill is intermediate in physical size between the smaller common crossbill and the larger parrot crossbill. While further studies to clarify its taxonomic status are being carried out, the Scottish crossbill is treated by scientists as a distinct species.

The crossbill feeds on pine seeds either by pulling a cone off a branch and then holding it with its feet while it uses its bill to extract the seeds, or it acrobatically moves around the cone, extracting the seeds without removing the cone from the branch. The location of a feeding crossbill can often be determined by the floating seed cases and occasional falling pine cones which result from its foraging. When crossbills are nesting, they will often favour particular pines near their nest which are heavily-laden with cones and will return to them repeatedly to feed.
Although pine seeds form the vast majority of their diet, crossbills occasionally feed on small shoots and buds, while in spring the females frequently feed on insects, to provide the extra protein needed to produce their eggs. Males feed on insects to a lesser extent than the females, but insects, including the larvae of the pine sawfly (Neodiprion sertifer), are sometimes brought to the young in the nest.

Loxia scotica occurs in the eastern Highlands of Scotland, UK, where it inhabits both semi-natural stands of Scots pine Pinus sylvestris and conifer plantations. Its core areas are Deeside, Strathspey and north-west of the Great Glen. Suitable semi-natural habitat has declined from approximately 15,000 km2 to fragments totalling 160 km2 over the last 5,000 years. However, the amount of plantation woodland has increased substantially during the 20th century. The size of the population is unknown but an estimate of 1,500 adult birds was made in the early 1970s and an estimate of 300-1250 pairs in 1988. It is likely that there are shifts in the distribution of the population in response to regional fluctuations in the cone crops of conifers, particularly those of Scots pine1,2. Its taxonomic status is unclear. Recent work on flight and excitement calls suggest that it can be distinguished from Common Crossbill L. curvirostra but whether it is distinct from Parrot Crossbill L. pytyopsittacus remains unclear. [conservation status from birdlife.org]

Courtship amongst crossbills begins in late winter or early spring when the males in a flock sing loudly and in chorus, with each individual seeking to broadcast his fitness for mating. They become aggressive towards each other, and will often fight for the right to mate with a female. When a female accepts a male, she will allow him to touch her bill with his, and the male will then feed her to confirm their partnership. Mating often takes place during the process of nest-building, which is done almost exclusively by the female, although males sometimes help in the initial stages of construction. Nests are usually situated high up in pine trees, 10-15 metres above the ground, although occasionally a stunted bog pine, no more than 5 metres tall, may be used. The nest itself is made from a base of twigs, upon which grass, straw and lichen are built up, followed by a lining of moss, feathers and animal hair or fur. Nesting has been observed in all months between February and June, with March and April being the main months when eggs are laid.
The clutch size varies from 2 to 6, with 4 eggs being the most common size. The key factor which determines the size of the clutch is the availability of pine seeds, and in years of poor cone production crossbill pairs may fail to breed at all. The female broods on the eggs for 13 to 15 days until they hatch, and during this period the male will feed her. Both birds feed the young, which leave the nest about 3 weeks after hatching. It is usually a further 10 days before the young birds' bills become crossed, so they still depend on their parents to provide them with pine seed during this period. After this, the family group will split up, although the young may stay with one or other of their parents, and, with them, may become part of a flock.

Resident and dispersive. In most years, birds disperse after breeding to seek better food supplies, settling in adjacent or fairly close woods or plantations in Scottish highlands. When large populations build up after several years of successful breeding, birds sometimes move further in general exodus; e.g. in summer of 1936 many birds in upper Strathspey dispersed in large flocks, and few remained there to breed in spring 1937.