The Doves are purchasable in the FarmVille Market for a limited amount of time (6 days) and can only be purchased with farm cash. They cost 12 FV$.
The Doves are more of a decoration similar to the White Owl. They have a neat "fly" feature, that involves an animation of one of the doves flying. However, unlike other FarmVille animals they do not harvestable or yield coins.
This article was reprinted with permission from FarmVille Freak.