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
Birds International is conducive to the breeding and propagation of exotic birds. Birds International provides captive-bred birds to pet lovers, hobbyist, zoos and parks. The company is evaluated to be "the biggest and most successful breeder of exotic birds in the world". It has 20,000 exotic birds at any given time. Most of them are exported to Asia, Europe and Japan. Prices can be high, making Birds International a successful business venture and thus a model for similar enterprises. It has also been pointed out as a model for aviculture industry in Australia where, as in the Philippines, commercial trade in native