Today one of my king pigeons is standing on one leg. Its other foot seems painful for it to use. Nothing in broken, but the toe ends seem swollen, and the nails are discoloured. It has problems gripping its perch with that foot. About a week ago its mate also had a bloody toe nail and was holding its leg up. She is OK now, but the toe seems stiff. What could be causing this? They have the same cage as always, I have checked the cage and everything is smooth and no things to get the toes stuck. Maybe they did it when landing on something in the garden? My other 4 pigeons are all in the same kind of cage and have free flight, but they are all ok. Is there a disease that causes lameness? I love my birds and now am worried about them - in particular the one only using one leg.