The decline of raptors in West Africa: long-term assessment and the role of protected areas.

摘要

Comparative large-scale roadside counts (8353 km), through Burkina Faso, Mali and Niger, conducted in 1969-73, were repeated 30-35 years later with the same observer and methodology and at the same season. The transect was divided into three geographical zones and between protected and unprotected areas. All diurnal raptors were recorded (22 801 individuals), as well as large game birds. Large vultures suffered a dramatic decline (98%) outside protected areas. The hooded vulture (Necrosyrtes monachus) population also collapsed in some regions, but survived in central Burkina Faso. Conversely, their abundance index did not decrease significantly in national parks. Four eagle species decreased by 86-93% and seven were not even recorded in the later study outside protected areas; by contrast, in national parks, only three species had declined marginally. Smaller Accipitridae (kites, goshawks, buzzards) also exhibited significant declines outside but not within national parks where woodland species reached their highest densities. The ommon kestrel (Falco tinnunculus), mostly European migrants, declined sharply everywhere. African falcons decreased only outside protected areas. Among Palaearctic migrants, Montagu's Circus pygargus and Pallid harriers (Circus macrourus) decreased significantly, short-toed eagle (Circaetus gallicus) less markedly, and marsh harrier (Circus aeruginosus) and booted eagle (Hieraaetus pennatus) not at all. Similar trends had previously been documented in Cameroon. They are associated with human population growth and development, global habitat degradation and ecosystem impoverishment (woodcutting, agricultural intensification, overgrazing, desertification). Heavy use of pesticides, control of locust outbreaks and overhunting have suppressed major food sources. Vultures may suffer from a shortage of carcasses, poisoning for predator control or persecution for trade of meat and body parts. Protected areas play a prominent role in the maintenance of vulture and eagle populations, even though they currently cover less than 2% of the Sudan zone and are virtually absent in the Sahel..