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 & Blooms of American adults were involved in gardening, and 6.4% were bird-watchers. In May 2005, "Birds & Blooms" began publishing "Birds & Blooms EXTRA" with magazine issues published six months a year on alternating months to the original "Birds & Bloom" magazine. Birds & Blooms Birds & Blooms is an American magazine about backyard plants, birds, butterflies, and other creatures. "Birds & Blooms" was started in 1995. The magazine has its editorial offices in Milwaukee, Wisconsin. The magazine is produced once every two months. Most of the articles and photographs in the magazine are reader-submitted, giving the magazine a non-scientific approach.