I used to have many pigeons around the house. If by chance one of the chicks fell out of the nest, we used to put it back using gloves.
Usually, if we would touch the chicks with our bare hands, however, the other pigeons would usually kill the chick. I want to know why they do that?
This is a story I have been told as well when I was a kid. Usually this is related to the foreign smell that the humans leave on the chick. However, this seems to be an urban legend, as birds have not a great sense of smell.
Snopes says about this:
However, Mother birds will not reject their babies because they smell human scent on them, nor will they refuse to set on eggs that have been handled by a person. Many birds have a limited sense of smell and cannot detect human scent, or if they can detect it, do not react to it.
What can happen is that the birds returning to their nest which find the nest disturbed compared to the situation when they left might cause them to temporarily or permanently abondon their nest.
You can find this and more urban legends about birds here and here.
