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 of the West Indies Birds of the West Indies Birds of the West Indies () is a book containing exhaustive coverage of the 400+ species of birds found in the Caribbean Sea, excluding the ABC islands, and Trinidad and Tobago, which are considered bio-geographically as part of South America. Written by ornithologist James Bond, the book was first published as "A Field Guide to the Birds of the West Indies" in 1936 by the Academy of Natural Sciences as part of the "International Series". It has been reprinted several times since then, including as one of the Peterson Field Guides series (PFG 18), a