Moa Nests can sometimes produce Moa Eggs needed for the Black Moa Chick miniature. When they do, you receive the message, "You quickly look around to make sure none of the nearby Moas are watching, snatch an egg from the nest, and quickly place it into your bag."
Note: Only one Moa Nest (the east-most) in Regent Valley actually produces an Egg. (This group of nests can be found due south of Fort Ranik.)