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
Thunder Birds (1942 film) censured than prettied, about an American instructor and a British flying cadet at the field who, in love with the same American lassie, vie to see which one can be the nobler goof." Audiences, however, were thrilled by the aerial scenes, which Crowther noted: " (contained) ... many shots of basic trainers rolling and zooming on yellow wings against the blue. Those are the only exalting glimpses in the whole film." Film historians consider "Thunder Birds" a classic aviation film. Notes Citations Bibliography Thunder Birds (1942 film) Thunder Birds (subtitled "Soldiers of the Air" and also known as Thunderbirds) is