Habitat use by the Grey Heron (Ardea cinerea) in eastern France.

We analyzed the spatial relationship between the location and the size of the 69 Grey Heron colonies existing in 1994 in refuge areas in eastern France after recolonisation following the decline of the species in the 19(th) century. We used five variables describing the hydrographical network, which are known to play a part in the location of the colonies in this area. The results showed that the distribution of the breeding colonies was not governed by the same elements of the hydrographical network. Three local strategies of spatial utilization were observed: the first one privileged the large but not dense rivers; the second, the dense network of small rivers; and the third, the ponds that were more restricted geographically. The spatial organization of the hydrographical elements is thus very important in the distribution and the size of the Grey Heron colonies.