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 and People aesthetic adornments and as expression of some unspoken bond between ourselves and the rest of nature. The resulting work is intended as a summary of the current state of birdlife worldwide. Cocker suggests that birds are the miner's canary for the natural world. However a further aim of the "Birds and People" project is to provide a panoramic survey of the multitudinous way in which birds enter and enrich human lives. "The forum aims to bring together first-hand accounts from the staff and members of BirdLife Partners, and from the wider public. The organisers hope that people from every country