Avian clutch size of increasing clutch size with increasing latitude. The proximate and ultimate causes for this pattern have been a subject of intense debate involving the ideas of group and individual selection. David Lack observed a direct relationship between latitude and avian clutch size. Birds near the equator laid approximately half as many eggs as those that resided in northern temperate habitats. He observed an increasing clutch-size from the equator towards the poles (something he referred to as the “latitude trend”) for many passerine (perching) birds, near-passerine (tree-dwelling) birds and in various other groups: Strigiformes, Falconiformes, Ciconiiformes, Laridae, Ralliformes, Galliformes, Podicipedifomes, and
Angry Birds Trilogy Management Pack available on December 18, 2012. Fowl Tempered Pack available on March 8, 2013. In "Angry Birds Trilogy" the player controls a flock of multi-colored birds that are attempting to retrieve their eggs, which have been stolen by a group of hungry green pigs (on the Angry Birds Rio levels, the birds are trying to get back to their eggs). On each level, the pigs (in Rio, caged birds or marmosets) are sheltered by structures made of various materials such as wood, glass, and stone, and the objective of the game is to eliminate them on the level. Using