We had a hatchling pigeon brought into our care this week. A look at his poo through the microscope showed that he was healthy, so he was placed with foster parents - two fancy pigeons who in spite of, ahem, quite regular and enthusiastic copulation, have never produced an egg of their own. (Not that we breed pigeons - with so many unwanted and in need of homes we provide dummy eggs for them to sit on instead).
Anyway, it seems the pair would never have been able to have babies of their own, but now they've been gifted with this orphan, they're extremely over-zealous parents. They often both sit on him at the same time, rather than taking shifts which is how pigeons usually parent their offspring.
Being reared by pigeons is obviously a much more natural experience for the baby than being reared by humans, he's allowed to bond with them freely, whilst we volunteers must always keep our distance to avoid imprinting.
It should also produce a much healthier baby - crop milk, which is produced by pigeons to feed their young, is extremely nutritious and packed full of antibodies and antioxidants.
It also means this pair get to enjoy raising a baby, and they certainly seem to be.