Regardless of whether the Scottish crossbill is a species or not, it is still a unique part of the biodiversity of Scotland and well worthy of conservation

RSPB Scotland's Dr Ron Summers

The distinct species of common and parrot crossbills have long been known in Britain.

However, scientists studying the birds in the ancient Caledonian pinewoods of Strathspey and other parts of northern Scotland began to suspect that they were observing three different groups of crossbills.

This third group, the "Scottish crossbill", has members with bill and wing sizes which are intermediate between the parrot and common crossbill groups, according to researchers.

Dr Summers and his colleagues found that all three types of crossbill select mates with the same size of bill, indicating that each acts as a true species.

The team also studied the crossbills' DNA, but found no differences between the three types.

Different species

A third study investigated the birds' calls, as the discovery of distinct calls among the different groups would support the idea of three separate species.

The team discovered that the Scottish crossbill has excitement calls which are distinct from the common and parrot crossbills.

The report's summary says that no definitive answer has been found to the species question.

However, it says the research carried out so far is lending weight to the recognition of a new species.

All three types of crossbill can be seen in RSPB Scotland's Abernethy Forest in Strathspey, where the research work continues.

Dr Summers said: "Regardless of whether the Scottish crossbill is a species or not, it is still a unique part of the biodiversity of Scotland and well worthy of conservation."