Vernon Briggs, age 15, of Arab, Ala., for his question:

WHAT IS PIGEON'S MILK?

There are 289 species of doves and pigeons, and they can be found throughout the nonpolar world. Some are as small as sparrows while others are as large as gamecocks.

Both mother and father build the nest when it's mating time. Mom usually sits on the nest during the night, handling the incubation chores, while dad takes over during the day. Two eggs hatch between 14 to 19 days.

The babies stay in the nest 12 to 18 days with both parents feeding them the first week or so, a regurgitated substance called pigeon's milk. The milk, a secretion of the crop lining, is injected when the adult inserts his bill inside the relatively large bill of the nestling.