15 February, 2016

How many Crossbill species we have here in Finland?

Parrot Crossbill in the crown of spruce

We had a very interesting presentation by Antero Lindholm in our local birding club meeting last week. He told us about Crossbills and as we all know, based on current understanding, we have 3 species of Crossbills here in Finland; Two-barred Crossbill (Loxia leucoptera), Red Crossbill (Loxia curvirostra) and Parrot Crossbill (Loxia pytyopsittacus).

But based on DNA tests and sound analysis, we may actually have 2-6 species of Crossbills... The situation is approximately so that the Red Crossbill can be divided into several sound groups, and each group has different types of calls and other sounds. Individuals belonging to these sound groups behave like a sort of species, in other words they mate mainly with the Crossbills that belong to the same sound group.

Some of these sound groups have also a small morphological differences in relation to the other groups, eg. in the United States the Red Crossbills that feed in Lodgepole Pines (Pinus contorta) have a bill that fits perfectly to cones of Lodgepole Pine. Similarly, in the forests of the Himalayan mountain there lives Red Crossbills that are quite different in appearance, their bill is much lower and in the photo the bird looked smaller than our local Red Crossbills.

So, the conclusion is that the Red Crossbills are now in the point of evolution where they may diverge into their own species, or not. The Parrot Crossbill could be the most highly differentiated. And even though we have learned that Parrot Crossbill eats pine seeds and Red Crossbills eat spruce seeds,  both species can be found feeding both in pines and spruces. There's no difference in DNA of Parrot Crossbills and Red Crossbills.... And how about Scottish Crossbill (Loxia scotica)? Forget it, it is just another group of Red / Parrot Crosbills. The DNA situation is the same also with Common Redpolls (Carduelis flammea) and Arctic Redpolls (Carduelis hornemanni), Common Cuckoo (Cuculus canorus) and Oriental Cuckoo (Cuculus optatus) and Common Swift (Apus apus) and Pallid Swift (Apus pallidus). So it could be time to lump these species... At least DNA studies pungent perception of species to whole new frames.

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