Injured Duck

[FreeChicken!]

Lately, two feral ducks (yes, they're definitely not originally wild) have been visiting us. They live in the creek behind my neighbor's house across the road, and every day they cross the road and come for food and clean water. I've never had ducks, but I have chickens, so I can usually spare some chicken food for the ducks. They've never gotten sick or hurt and they're been really careful on the road.
But today, when I went to feed my chickens, and the two ducks visited as usual, the big black duck was standing on one foot. My roosters sometimes stand on one foot, so I didn't think there was anything wrong. Then the black duck took a few steps forward, and saw that he was limping pretty heavily.
The ducks don't mind me coming close to them while they eat, so long as I stay about a foot away from the black duck and about three feet away from the gray one. So I quickly got food for them, got down on my hands and knees, and observed the black duck's foot. It seems that the bottom of his foot is swollen and pale yellow. It's obviously putting him through a lot of pain, too.
What's wrong with his foot? What can I do for him? How can I grab him and hold him still long enough to help?

 

[FreeChicken!]

Anyone?

 

[Habibs Hens]

looks like bumble foot

he will die if not treated

try catch him treat him and if you are defo sure they are not fereal keep them

and give them a nice retirement

 

[FreeChicken!]

My friend and I caught him last night (his feathers are so soft!) and inspected his foot, but he stopped limping and the swelling went down. It's strange... Any explanations?