This bird was caught in lower Deeside in October 2007. As can be seen it has an intermediate bill, downcurved culmen and plumage that can be indicative of a pine crossbill. It gave both EcE and Fc4 on release, both classified as curvirostra.
Just to prove the point further, here is a Scottish Crossbill caught in October 2006. This has an intermediate bill that is downcurved (though not as much as the common above !) but has more orangey-red plumage ! This gave a Scottish Fc3 on release:
Hopefully this will illustrate the potential difficulty in separating these forms to species level, and even with considerable experience for some individual specimens it will be necessary to have all the evidence including biometrics and bioacoustic.