Raptor population monitoring: examples from migration watchsites in North America

Bildstein K.L., . Farmer J. C., Yosef R.

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Abstract:

Raptors are popular birds and they often serve as flagship species for broader conservation efforts. Unfortunately, they are secretive, wide-ranging, and area-sensitive species that can be logistically diffcult and fnancially prohibitive to survey and monitor. Raptors often congregate during migration however, and one cost-effective way of monitoring them is to sample their numbers at “migration bottlenecks” along migration corridors. The value of doing so is exemplifed by counts at Hawk Mountain Sanctuary in Pennsylvania, USA. These counts, begun in 1934, tracked “Pesticide Era” declines in regional populations of Bald Eagles (Haliaeetus leucocephalus) and Peregrine Falcons (Falco peregrinus), as well as recoveries in both species after DDT was banned in 1972. Today, migration hotspots at Hawk Mountain; Cape May, New Jersey; Veracruz, Mexico; and Talamanca, Costa Rica; together with > 50 additional sites, monitor migratory populations of North American raptors. The Raptor Population Index (RPI), a collaboration involving Hawk Mountain Sanctuary, Hawkwatch International, and the Hawk Migration Association of North America, is analyzing count data from sites throughout North America. In 2008 RPI published a “State of North America’s Birds of Prey” that uses these analyses, together with data from Breeding Bird Surveys and Christmas Bird Counts, to summarize the conservation status of North American raptors. The counts also will be used to track shifts in the timing of migration that may be linked to climate change. Many of the data used in these analyses have been collected by amateur raptor watchers. Similar efforts in Europe and the Mediterranean should yield similar results. Migration watchsites such as Falsterbo, Organbidexka, Tarifa, Gibraltar, Col de Bretolet, the Straits of Messina, Burgas, Istanbul, the Northern Valleys (Israel), Eilat, and others -together with data from additional censuses and surveys- offer the chance to build a large-scale monitoring scheme for Europe’s 38 species of migratory birds of prey. We suggest ways for establishing large-scale raptor monitoring in Europe and the Mediterranean region.