Hey there, sorry about the delay.
So I'm guessing that this is frostbite, and a really nasty case too. Whats weird is that I was away from home only twenty four hours, but the black spots practically tripled in size, and the poor birds feet were already hardening. I put some probiotics on them...
Wow, thanks for the quick reply! There were definitely some on the top of the feet, mostly on the webbing. I believe he may have had some on the bottom too, but unfortunately I am out of town currently, and I don't remember for certain. I'll be home tomorrow, and I'll be sure to take a few...
Curious to see if anyone with more experience may have some insight into this strange situation. I have a Muscovy duck about five months old who I recently brought inside because his feet were getting really cold and were partially frozen (red and stiff). He was tripping over himself too...