| Identifying Parrot Crossbills |
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Telling Parrot Crossbills Loxia pytyopsittacus and Common Crossbills L. curvirostra
apart requires good views and is not always easy. The problem is
actually even more complex than some fieldguides indicate, owing to the
variation in bill shape of Common Crossbill. Some Commons are text-book
birds, with fine and pointed bills with the bill-tips well overlapping,
while others have a much deeper and heavier bill, and are thus much
more similar to Parrot Crossbill. These deep-billed Common
Crossbills are often misidentified as Parrots by less experienced
birders. I've started to call the two types of Common Crossbill "Spruce Crossbills" and "Pine Crossbills" respectively, not really based on anything, but rather to keep to two types apart (and also because, at least in theory, the heavier billed Pine Crossbills seem better adapted to feed on pine cones and the finer billed Spruce Crossbill on spruce cones). Interestingly, these birds also seem to sound different. The flight calls of the fine billed birds are the diagnostic, rather liquid "glipp-glip-glip"-sounds normally connected with Common Crossbill, while the Pine type has a deeper sound, which is rather similar to the call of Parrot Crossbill (personally I'm not capable of separating the flight calls of Parrot and a "Pine" type Common Crossbill, they are just too similar to my ears; For those seriously interested in Crossbill vocalisations I can recommend Magnus Robb's detailed paper in Dutch Birding 22:61-108, with an accompanying sound-CD). Another interesting thing with these irruptive and irregularly appearing birds is that the two types seem to turn up in different years and different areas, maybe responding to differences in the local crops of spruce and pine cones. Sometimes the spruce-type is common in the north and the pine-type in the south. Next year the pine-type may occur in the north, while the south has no crosbills at all. This may suggest that the two types actually represent rather well isolated populations coming from different core areas -only a wild guess at the moment, which surely the future will prove right or wrong. And then to the question of how to recognise a real Parrot Crossbill? Rather thantrying to sort out the bill, look at the bird as a whole in order to assess the proportional size of the head. The Parrot Crossbill is a really big-headed bird, which may actually dwarf its bill! The rule of thumb is, that the head of a Parrot Crossbill is about half the size of the entire body (exluding wing- and tail-tips), which means that the head counts for a third of the entire bird! The Common Crossbill, regardless of bill type, is just like any other finch, with a comparatively smaller head, only about a third of the bird's body size.  Parrot Crossbills. Note how big-headed some of the birds appear and how small and round the bill looks.  Big-headed Parrot Crossbills.  Parrot Crossbill. Because of the big head the eye often appears small on Parrot Crossbills. Note the almost angled shape of the lower mandible. Apart from the fine-billed type of Common Crossbill, which is easily identified on bill structure alone, most crossbills will have bills, which are much more difficult to assess. One Parrot Crossbill feature, which seems to be rather constant, is the distinctly curved, almost angled contour-line of the lower mandible. In Common Crossbill the outline of the lower mandible is much more gently curved, which gives the whole bill a more "normal" look.  Male Common Crossbill of the fine-billed "spruce"-type. This picture is not the best one to illustrate the features mentioned in the text, but at least the rather fine bill with a gently curved lower mandible shows well. This bird is relaxed, with nape feathers fluffed out, and looks therefore big-headed in the picture. Even the behaviour of the birds might give a clue. Parrot Crossbills can be quite confiding feeding peacefully only metres away from people, sometimes low in trees, but so far I have never yet come across a party of feeding Common Crossbills, which would have let me any closer than finches in general. Something worth considering. |
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