Sometimes a pigeon's upper beak will longer than it should, usually in a downward curve or a hook. This will eventually make picking up seed impossible and the pigeon will become starved.
Beaks can be trimmed or filed to a more acceptable length, but trimming too far back can cause a serious bleed so trim off a tiny bit at a time
On white beaks identifying how much can be trimmed safely is relatively simple as the overgrown bit will be transparent making it easy to see where the blood supply starts , but in dark beaks it is much more difficult and it might be best to ask a veterinary nurse to do the job the first time so that you can observe!.
If you plan to trim a beak yourself have a supply of Cornflour ready and dip the beak in it if it starts to bleed and trim off only a fraction at a time, wiping your finger over the end of the beak each time. If there is the tiniest trace of blood on your finger, then stop..
File down any rough bits. The trimmed beak is likely to overgrow again so pigeons with this condition would be better kept as pets or placed in the permanent care of a sanctuary.