Hello and thanks for your inquiry. Although we don't currently have any experts available at the moment to specifically diagnose what's going on with this pigeon's toes, I believe the lumps may in fact be calcified feces. Apparently this happens in young birds and/or birds with pre-existing foot/toe injuries. Sort of like a snowball, as the bird continues to step in bird feces, it hardens and builds up around their toes. I found this website with some advice on removing the lumps (maybe only possible if it's a captive bird); also copied text from website below.

"Hard ball of poop on pigeon’s foot – toes

This happens quite often when pigeons have injured or deformed feet. they step in poop and gradually a rock-hard ball of poop forms, which is heavy and uncomfortable for the bird.

Don’t try to pull the ball off immediately as this could damage the nail sheath. Instead, dissolve a tablespoon of salt in warm water and place the pigeon’s foot in it to soak. This loosens the hold that the poop has on the toe very quickly and you will be able to slip the ball off with no pain or damage to the pigeon .

This saline mix is also useful when you have caked formula on the feathers of baby pigeons, just dampen the affected areas and wipe with a damp cloth."