Richesse comparée des peuplements d’oiseaux en milieux hétérogènes pour différentes densités de points d’écoute

Abstract

A comparison is made between two methods of systematic sampling, using the resident populations of Mont Pilat Regional Park, France, as an example. Although mostly covered by an evergreen forest, the study area was made of a mosaic of different habitats. 212 “ census spots” (points d’écoute) were first selected at random on a rectangular grid whose lines were 1.6 km apart. Identification (by sound) of resident birds was made during 20 minutes, once during the breeding season on each “ census spot”. 84 species of resident birds were identified in this way. These results are compared with those obtained by a simpler technique, where a smaller number of “census spots” (23 and 24) were selected at random on a wider grid (5 X 5.6 km) laid in the same study area. The duration of the single census period was also limited to 10 minutes in this instance. Such a simplified technique enabled a smaller number of species to be identified (56 and 52 respectively). 150 “census spots”, each of a 20 minutes duration, are shown to be able to detect 95 % of the resident bird species in such a mosaic of habitats.