Читать книгу Ecology - Michael Begon - Страница 142

Having seen that many species compete for territories related to the availability of resources rather than for the resources themselves, it is perhaps not surprising that when we come to manage such species, ensuring the availability of territories is a top priority. A good example comes from a study of bearded vultures, Gypaetus barbatus, which became extinct in the European Alps more than a century ago, and have been the focus of a reintroduction programme since 1986 (Figure 5.35). Captive‐reared individuals were released from four widely dispersed sites from which they spread to new areas, and this spread was monitored in the Valais region of Switzerland (not one of the release sites). During an initial phase, from 1987 to 1994, the sightings were of subadults, and the most important factor explaining the distribution of these sightings was the biomass of ibex, Capra ibex, whose carcasses are an important resource for the vultures. However, during the subsequent phase, from 1995 to 2001, when adults were finally settling in the region, the presence of the vultures was most closely correlated with the distribution of craggy limestone crags, which are the ideal base for their territories, providing nest sites, thermal conditions for soaring, and limestone screes for bone breaking and food storage. Food availability was of only secondary significance. It seems clear, therefore, that future reintroductions in the area should focus precisely on the availability of these viable territories.

Figure 5.35 The importance of good territories for the conservation of bearded vultures. Map of the Valais region of Switzerland, where bearded vultures, Gypaetus barbatus, have spread following their reintroduction. Black squares are 1 km squares where juvenile vultures were sighted during an initial, ‘prospecting’ stage (1987–94). White circles are 1 km squares where adult vultures were sighted during a subsequent, ‘settling’ stage (1995–2001).

Source: After Hirzel et al. (2004).