[citation needed] Research in Scotland has shown that red, parrot and Scottish crossbills are reproductively isolated, and the diagnostic calls and bill dimensions have not been lost.

[citation needed] The Scottish crossbill breeds in the native Scots pine (Pinus sylvestris), Caledonian forests of the Scottish Highlands, but often also in forestry plantations of exotic conifers, notably Larch (Larix decidua and L. kaempferi) and Lodgepole pine (Pinus contorta).

[citation needed] Adult males tend to be red or orange in colour, and females green or yellow, but there is much variation.

[citation needed] The Scottish crossbill is extremely difficult to separate from the red and parrot, and plumage distinctions are negligible.

to be the method used by the birds to make sure that, especially given the physical similarities with other crossbills, they only attract and pair with potential mates of the same species.

This provides the basis for a method to survey crossbills and, for the first time, gain a clear picture of their numbers and distribution in Scotland and help in any conservation programmes for the race.

[12] Despite lacking data for population trends, British Birds places the crossbill on their Amber list for conservation concern on the basis of it being an endemic species and therefore of 'international importance'.

[16] One of the main threats to the crossbill's habitat is wood and pulp plantations, plus underplanting conifers and grazing pressure.