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 Seasons birds and the pigs unless they are inside them. On December 1, Winter Wonderham was released and was the 3rd Christmas episode in the series. Like the other Christmas episodes, it is set up as an advent calendar. It introduced slippery blue ice, that makes wood, ice, stone, birds and pigs slip on contact. Season 2013 began in May 2013, when Abra-Ca-Bacon based on World Circus Day was released; it has a magician theme and features magic portals, which can teleport materials, birds, or pigs from one portal to another. In December 2013 Arctic Eggspedition was released, the 4th Christmas