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
Human uses of birds from many people with differing perspectives. Among them, the society's science director, Gary Langham, noted that what is good for birds is also good for humans. The writer David Allen Sibley observed that birds bring a little wildness into parks and gardens. The writer Barbara Kingsolver noted that birds are part of life on earth. The actress Jane Alexander wrote "Birds remind us that there are angels." The forensic ornithologist Carla Dove noted that birds are biological indicators of habitat health, climate change, and the coming of spring. Birds have been seen as symbols, and used as such, though perceptions