Why such a strange beak?

Bird Watching (UK) - - Your View -

May I have your ob­ser­va­tions on the at­tached photo taken in our rear gar­den. I have seen im­ages with ex­tended up­per beaks but nowhere near as long as this one. The bird seemed to be feed­ing well. How and why does this hap­pen, please? Jack Hans­ley, Sax­ilby, Lin­coln

QAb­nor­mal­i­ties in wild birds are quite rare, but when they do oc­cur it is usu­ally the feet or beak that are af­fected. Lower bill de­for­mi­ties are less com­mon than up­per bill de­for­mi­ties but do oc­cur, and there are var­i­ous causes. Some are caused by de­fi­cien­cies in diet, or by chem­i­cal poi­son­ing, but the com­mon­est cause seems to be dam­age to the beak. In the case of your Rook, we think that the bird has at some point bro­ken off the tip of its up­per beak. As birds’ beaks grow fairly con­tin­u­ously, this will have caused the lower mandible to grow past the up­per, and be­gin to curve up­wards, while the up­per beak grows back. As long as the bird suf­fers no more dam­age and can feed nor­mally, there is no rea­son why it won’t sur­vive quite well, al­though it may have a few prob­lems groom­ing it­self.

A

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