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Message: <blockquote data-quote="bombycilla" data-source="post: 1940021" data-attributes="member: 72567">I am not saying it doesn't happen but in retrap crossbills that I have processed their calls are identical to what they were up to 4 years previously. I also have recordings of colour ringed birds in the field and again these calls in situ match the ones that they gave when first caught. So it can't be commonplace.I also think we have to be careful about using terms like "call switching". I prefer 'call syncing' as this more accurately represents the position ( I think). I am more interested in whether a shift in the calls themselves (within a population) can occur as seems to have happened with Scottish Crossbill.As I recall ( I may be wrong) but in at least one (?) of the very few instancea of UK mixed pair breeding crossbills, the birds were identified as being different on the (different) calls they gave. As previously I can't argue with the genetic data at this point.</blockquote>