Matthew Young posted to the Finches, Irruptions, and Mast Crops facebook
page the following comments and link:
Introducing the Newest Red Crossbill Call Type, Type 12.
Red Crossbills continue to pose an interesting puzzle to biologists —
while also highlighting the importance of birders and citizen scientists
to science. We hope that this research encourages birders to continue
exploring conifer habitats. And of course, keep recording those crossbills!
The link provides a great overview of the complexity of the Red