BirdForum is the net's largest birding community dedicated to wild birds and birding, and is absolutely FREE!

Register for an account to take part in lively discussions in the forum, post your pictures in the gallery and more.

Reply to thread

Message: <blockquote data-quote="bombycilla" data-source="post: 1938996" data-attributes="member: 72567">I agree that science is all about measuring and quantifying differences, but I am not a fan of describing Crossbill species solely on "mean" bill depths, due to the massive variation or "range" of depths that can be present - birds in the overlap could potentially be of several types. Certainly here in Scotland the "overlap" is not restricted to a minority of specimens, quite the opposte ! In fact the overlap can be pretty extensive both sides of the mean which is what causes the problems with Common, Scottish and Parrot Crossbill. If you use calls to diagnose 'speciation' then you have some Parrot Crossbills with minimum bill depths of 11.9mm, well within the range of Scottish Crossbill. If you hadn't used a call, then it would probably be Scottish on historical and published biometrics.My position is that data sets and slide rules are not the best components of Crossbill 'speciation' (if they are even species). Let's call it 'classification' - that would be cultural aspects (calls), breeding behaviour and ecological factors (where they are found, what they feed on etc) with biometric data factored in, though I don't think the 'minimum bill depth is a brilliant measurement of bill 'fitness' from my experience in Scotland.Another thing - a Crossbill 'type' may be specialized to feed on a particular cone/seed, but that doesn't mean it can't survive on others....and whi ch is why a given population has variation in the first place.THIS <a href="http://pinemuncher.blogspot.com/2009/09/thats-life.html" target="_blank">http://pinemuncher.blogspot.com/2009/09/thats-life.html</a>discussed the 'Scottish problem' and natural variation in that population a year ago with similar content to what is being discussed on here.</blockquote>

Verification