Comparing hatchlings and nestlings
In the UK the baby pigeons/doves that you are most likely to come across usually due to nest destruction or nest predation – are the wood pigeon, the feral pigeon , the collared dove and the stock dove. However, baby feral pigeons often need rescuing when their nests are destroyed by pest controllers or property owners . This is what each of those look like :
Baby wood pigeon:
even at this age you can see the first white feathers which will form his white wing band sprouting at the bottom edge of his wing. The white neck ring won’t appear until it is an adult.
The baby wood pigeon will have a large black beak
A video of a wood pigeon hatchling:
Baby collared dove : 
Collared doves are smaller than wood pigeons, sandier and have brown spidery feet.
The collar doesn’t appear until they are adults. Their beaks are a paler colour than the wood pigeon baby.
The baby in the photo below had already doubled in size in a day.
I collected this one from the vet. They wondered whether she was too young to stand a chance, but even newly hatched ones have thrived with human care!
Baby feral pigeon: Feral pigeons come in different colours. They grow very quickly, these are 12 days old.
Stock Dove Nestling:
This sweet baby was found out of the nest and taken to Folly Wildlife Rescue in Kent where it was hand raised (photo kindly supplied by Revati Poole).
Stock doves all look alike and can be confused with the feral pigeon, but they have a pinkish breast similar to that of the wood pigeon.
They have very dark eyes, often seen as black.
The adults will have a very bright band of iridescent green (sometimes looks purple) on its neck, but this will be missing in the younger birds.