I have a rowan tree in the back garden. And it's still heavy with berries. Usually the birds would have attacked them by now. Is this unusual, when lots of other trees have lost their leaves etc?
I too have noticed some well ladened rowans on my travels, it seems there is a glut of fruit this year on many trees and shrubs, too much competition in other places maybe ?
I think the most likely answer is that the birds will find them more palatable after a few degrees of frost, which may sweeten the flesh of the berries.
The birds here haven't really started on the winter berries this year yet either. I think its because the warm weather has lasted for so long that there has been plenty of choice for them.