From the rule book:
"Egg On - A mating game for screwy birds
In this game, the players slip on the feathers of a male bird. Through the use of bridal gifts (worms) they try to convince the stunning females (in the middle of the table) that they would be the best fathers for their eggs. During the course of the game, the males try to mate with the females in order to achieve paternity over certain eggs. However, not all the eggs are equally valuable. The first egg in a nest scores fewer points than the third. Also, there are females who are better suited for mating (they have matching color) and their eggs thus earn a bonus.
The King of the Nest will, without a doubt, be the one who manages to mate with all the females, i.e. to collect eggs in all the colors."