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
Killing Birds Soavi, who had direted "Stage Fright" for him in 1987, to direct "Killing Birds" next. However, Soavi chose to direct "The Church" instead when "Lamberto Bava" decided not to do it as part of his "Demons" series. Soavi's assistant director on "Stage Fright", Claudio Lattanzi, was used as director for "Killing Birds". There are differing testimonies as to how D'Amato and Lattanzi shared in directing the film: The film was released theatrically in Italy through "DMV distribuzione" in 1988 under the English title "Killing Birds" and later on home video: on VHS by "Magnum 3B" under the title "Killing Birds: