The animals who feed their young ones are referred as mammals.
Except bat, none of the birds are classified under mammals.
That means birds don't breast feed their children !!!!
But there are handful of birds that are evolved to produce a substance known as crop milk !!!
Crop milk is not the milk similar to the milk mammals produce.
Crop milk is a nutrient rich secretion produced from the lining of crop which is a pouch in throat area.
Despite its name, crop milk is not a true milk but a secretion rich in proteins and fats.
Here are the special birds which produce crop milk -----
1. Pigeons
2. Doves
3. Flamingos
4. Emperor penguins