Can you use a chicken coop for Pigeons. You certainly can, though there are some significant differences in HOW it is used, and Pigeons have different space requirements than chickens.

Probably the biggest difference is that Chickens SHARE a nestbox between several chickens. Pigeons do NOT share. They are territorial.

Chickens also share a rooster. Pigeons do not. Pigeons mate for life (well, mostly). So you need one Pigeon Cock for every Pigeon Hen, and they'll pair up.

Because Pigeons are territorial and do not share, you need one nest box for every pair. A couple WILL share with each other. They just won't share with anyone else!

Pigeons also FLY. Oh, some chickens do (mostly Bantams), but it is mostly just short flights to get from one perch to another, or to get up on the roof if you are trying to catch them. They like their nest boxes up higher than chickens do. They like their roosts higher too. These things though, are compromise issues - if you have a coop that has floor level nest boxes, and a perch that is a foot off the floor, they'll still use it.

When deciding on how much space you need, simply use the requirement for Bantam Chickens. If a coop says it will hold 4 Bantams, then it has enough room for two pair of Pigeons.

Pigeons do not drink the same as chickens do. Chickens scoop water and then tip their head back to swallow. Pigeons SIP water. This means that Chickens can use a nipple or drip watering system, while Pigeons cannot. They need something deep enough to stick their bills into so they can drink. Otherwise, they'll dehydrate and die. Some coops have watering systems built into them - make sure it is one that works with Pigeons if it has that.

A Chicken coop isn't the ideal environment for Pigeons, but if that is what you have, then it can be made to work. Just keep the requirements for Pigeons in mind, and not the requirements for Chickens when you select or modify it.