In Britain some restrained satisfaction may be felt over recent trends in bird of prey populations. After 150 years in which human per secution caused massive declines in numbers and ranges in most of our predators, protection had begun to lead to some improvements when, in the 1950's, the new threat of persistent pesticides appeared. Marked decreases occurred in some species, especially the Peregrine Falco peregrinus and the Sparrowhawk Accipiter nisus, and widespread reductions in breeding success led to fears for the survival of the former (indeed it vanished from eastern North America before the danger was fully realised). In recent years, increasingly severe restrictions on the use of the persistent organochlorines, after bitter debates with some of the commercial interests, have led to welcome recoveries in the species affected, although even now Peregrine numbers are only some 60% of the pre-war level.
Under protection the Osprey Pandion haliaetus has returned, the Red Kite Milvus milvus is increasing and the Snowy Owl Nyctea scandiaca maintains a precarious foothold, but the Merlin Falco columbarius and Barn Owl Tyto alba also suffered declines due to pesticides, while the Montagu's Harrier Circus pygargus is virtually extinct here. Moreover, although all species enjoy full legal protection, the law is frequently ignored, most importantly by game preservers (some using the illegal and barbarous pole-trap), while egg-collectors and some falconers menace the rarer species. There is less cause for satisfaction when the global picture is examined, as became abundantly clear during the first World Conference on Birds of Prey, organised by the International Council for Bird Preservation (supported by the international organisations representing hunters and falconers, as well as by international governmental agencies and international conservation bodies) and held in Vienna from 1st to 3rd October 1975.