Unique to the Caledonian pine forests of the Scottish Highlands, the Scottish crossbill is the UK mainland’s only endemic bird species that is not found anywhere else in the world. Visually, it’s relatively hard to distinguish Scottish crossbills from the two other crossbill species (common crossbill and parrot crossbill) found in the UK.
As you might expect from its name, the Scottish crossbill’s crossed-over beak tips are one of the species’ key distinguishing features.
However, other features including plumage and observing habitat and behaviour will help you some way towards a confident and positive identification.
Male Scottish crossbills have a striking red plumage, with a darker brick-red seen on the nape and rump, and more orange-red shades dominating across the face and breast and belly.
The Scottish crossbill’s upper wings are blackish-brown, changing to a reddish-brown towards the tips. The tail is brown, but finely lined with red, while the underside of the tail is whitish.
The bill of a Scottish crossbill is a horn-grey colour, with the top and bottom mandible crossing sharply at the tip. Its legs are brown and it has dark brown to black eyes.
In this species, males and females are unalike and cannot be confused. Female Scottish crossbills have an olive-green crown and upperparts. The face is heavily streaked with darker markings, while the breast and nape feature some yellow colouring, which is also present on the throat and chin.
The female’s wings and tail are a dark brown-black, edged with olive green. Their eyes, bill and legs are the same as the males of the species.
Until they reach maturity, juvenile Scottish crossbills have a streaky green appearance. Young females are a lighter green in colour, with some yellow streaks, while males are a darker shade of green, marked with darker olive green.
After their first winter and into their first summer, juvenile males are beginning to develop a bit more of their adult orange-red colouring, which is fully acquired in their second winter or second summer.
Male Scottish Crossbill
Female Scottish Crossbill
All three of the UK’s crossbill species are similar in size as well as appearance, with the Scottish crossbill slotting in between the slightly larger and heavier parrot crossbill and the marginally smaller common crossbill.
There is no difference in size between male and female Scottish crossbills.
Scottish crossbills are often heard in song from high perches in conifer branches.
Their signature vocalisations include a loud, chipping ‘jip jip’ call and a rolling and varied melody, for example, "tiup rrreee priooo", which was fundamental to Scottish crossbills being named as a stand-alone species in 2006, rather than being a subspecies of a common crossbill.
Although similar in sound, Scottish crossbills and parrot crossbills can be told apart by their calls, with the cry of the latter species deeper in pitch. In turn, the Scottish crossbill’s ‘toop/choop’ call is lower in pitch than that of the common crossbill.
Pine seeds are the staple element in a Scottish crossbill’s diet, and their curved, overlapping bills are well adapted for extracting the tiniest seeds from a closed pine cone.
Additionally, seeds, buds, blossom and shoots from other evergreen species, including larch and spruce, may also be eaten.
Stripping tiny seeds from a pine cone is thirsty work and access to regular drinking water is vital for Scottish crossbills.
While raising young, the diet of adult crossbills may expand to include insects, such as the larvae of the pine sawfly.
Young Scottish crossbills are fed on regurgitated pine seeds, which are occasionally supplemented with insects and larvae foraged from among the pine forest habitats.
Scottish Crossbill feeding on pine seeds
Breeding habitats favoured by Scottish crossbills include lowland forests dominated by Scots pine, in both ancient Caledonian woodland and more recently established maturing coniferous plantations.
During winter, some short-distance movement occurs, driven by the availability of foods. Larch, lodgepole pine and sitka spruce plantations are among the most popular winter habitats.
Scottish crossbills are endemic to the far north-eastern and northern corner of the Scottish Highlands.
If you spot a bird that you think might be a Scottish crossbill outside of this specific geographic area, it’s more likely that it’s the closely related common crossbill as their distribution range is far wider.
Scottish crossbills are not found outside of Scotland, and even within Scotland, their range is limited to tracts of ancient Caledonian forest in the Scottish Highlands, as well as coniferous plantations that have been established in this region.
Around 6,800 pairs of Scottish crossbills are resident in north and north-eastern Scotland, making them a far less common species than the more widespread common crossbill, which has a population of up to 26,000 pairs.
Scottish crossbills have very limited distribution and are only resident within a specific area of north and north-eastern Scotland, The Cairngorms National Park is a particular stronghold, and localities that regularly report sightings to include Glenmore, Rothiemurchus, Abernethy, and Grantown.
Scottish Crossbill peeking out from the pine trees
The average lifespan of a Scottish crossbill is around two to three years.
First-time breeding is thought to occur in one-year-old birds, although younger birds are believed to have a lower rate of success when raising young, particularly if they have not acquired their full adult plumage.
Scottish crossbills have Schedule I status under the Wildlife and Countryside Act, 1981.
This offers protection against the destruction and damage of their eggs and nests, as well as wider protection against adult birds being knowingly killed, injured, or taken into captivity.
Around 6,800 pairs of Scottish crossbills breed in the UK each year, and the species has Amber status on the British Birds of Conservation Concern list.
They are considered a species of least concern and population estimates are encouraging, suggesting an increase in the 20th century due to an increased number of maturing conifer plantations in the Scottish Highlands.
Scottish crossbills build bulky, cup-shaped nests high in the branches of Scots pine trees, around 6 m to 8 m (20 ft to 26 ft) above the ground).
Nests are made from twigs from evergreen trees and padded out with heather, grass, moss, lichens, leaves, animal fur, and bark, and lined with feathers. Occasionally nests may also be built in an alternative tree species, including larch, spruce, or Douglas fir.
The nesting season for Scottish crossbills is among the earliest of all British breeding birds, with nesting routinely from February onwards, and occasional reports of laying as early as late January.
The peak laying months are March and April, and breeding can extend into June for second broods.
Scottish crossbills’ eggs are pale blue with purple markings; they measure 22 mm by 16 mm (0.8 in by 0.6 in).
A typical clutch contains 2 to 5 eggs, which are then incubated by the female alone for between 13 and 15 days.
All indications point to Scottish crossbill pairings lasting for the length of time it takes to raise one single brood.
It’s not unusual for a female to raise two broods in a year, but there is no evidence of pairs remaining together to raise further broods once their initial brood has fledged.
Scottish Crossbill perching on the branch of a pine tree
While the breeding season is ongoing, Scottish crossbill males will aggressively defend their mates and will challenge any encroachment on their territory.
While courtship displays are underway, males in particular have the tendency to behave aggressively towards each other.
In the non-breeding season, things change, however, and it’s not unusual for adult birds to join loose mixed-species foraging flocks through the winter.
Scottish crossbills are non-migratory and live and breed solely in the Scottish Highlands.
Some local dispersal may occur at the end of the breeding season, with birds travelling to different feeding sites within 20 km (12 mi) of their nesting grounds.
By February, they are back on their familiar breeding grounds, showing strong fidelity to nest sites used in previous years.
Scottish crossbills hold the unique claim to being the UK’s only endemic species of bird and are not found anywhere else in the world.
They do not migrate away from their native territory in pine forests in the Highlands of Scotland and spend their entire lives within around 20 km of where they hatched.
16cm to 17cm
27cm to 37cm
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