Pattern analysis of red-footed falcon ( Falco vespertinus) nests in the rook ( Corvus frugilegus) colony near Torda (Voivodina, Yugoslavia), using fuzzy correspondences and entropy

Abstract

In a planted poplar wood ( Populus spp.) near the village Torda (Yugoslavia) in 1990 and 1991 red-footed falcons ( Falco vespertinus) were nesting in the abandoned nests of rooks ( Corvus frugilegus). In both years we made a census of trees in the wood, rook nests and nests occupied by red-footed falcons, kestrels ( Falco tinnunculus) and long-eared owls ( Asio otus). For a mathematical description of the spatial distribution of nests we applied fuzzy correspondences. We used the theory of entropy for finding connections between the distributions of trees and rook nests and between these nests and those occupied by red-footed falcons. In 1991 the number of trees as well as rook nests was lower than in 1990. The proportion of trees with nests was 16.6% in 1990 and 10.8% in 1991. In this colony in 1990 and 1991, respectively, 20 and 14 pairs of red-footed falcons nested. They occupied 8.16 and 10.61% of available nests. We can conclude that the nests of rook for some reason (maybe because of a decreasing number of trees in the wood) concentrated in groups more during the second year. However, it turned out that the uncertainty of the spread of nests of red-footed falcons as compared with rooks was approximately the same for both years. The corresponding distribution of nests occupied by red-footed falcons was almost uniform.