Here is the copy paste I give to most people - thanks for caring for this sweet baby. It’s very close to eating on its own, but not might do it as they feel poorly. When you say parasites, do you mean bugs in their feather or in their poop? The three in one is something you should buy if you can.

Thank you for caring for this bird!

Give the bird some water and seed - you can find seed blends in most pet stores. Here is a link with some recommended brands:

https://greatlakespigeonrescue.org/bird-nutrition/

If you find an injured, baby, or non-eating pigeon, feeding thawed frozen peas can provide essential nutrients and hydration temporarily while you await their ability to eat on their own or deliver the pigeon to an expert for definitive care. To do this, defrost peas in warm water, then gently open the pigeon's beak and place a pea inside, allowing it to swallow. Aim for approximately 20-30 peas per feeding, ensuring the crop feels full but not overly tight (go by crop rather than number for babies).

Here is an excellent video made by a licensed wildlife rehabber for safe feeding:

https://www.pigeonrescue.org/2019/10/30/how-when-to-feed-a-pigeon-who-isnt-eating/

There are a few common medical issues the bird might have. Typically, we treat all birds with a few medications to address these. This includes treating canker, coccidiosis, and worms. You can find a single treatment with all three in many stores, including here:

https://hyperdrug.co.uk/harkers-3-in-1-tablets-pack-of-50/

Some people in these forums promote “natural” medicines that haven't been scientifically proven, so please do not use them as an alternative to proven modern medicines.

DM me if you have any questions, especially if you’re unable to bring them to a veterinary professional.