SELECTION AND REUSE OF NEST STANDS BY SPARROWHAWKS ACCIPITER-NISUS INRELATION TO NATURAL AND MANIPULATED VARIATION IN TREE DENSITY

The difference between nest stands of Sparrowhawks Accipiter nisus in southern Norway and randomly sampled control plots was best explained by tree density, being much higher in nest stand plots than in control plots. Other characteristics of Sparrowhawk nest stands, such as fore st age, tree species composition, and altitude were less important and implicated only through their correlation between these habitat varia bles and tree density. The reuse of thinned nest stands was lower than for unthinned nest stands, and only spruce-dominated nest stands were reused after thinning. At unthinned nest stands, both forest age, num ber of trees and breeding success influenced the frequency of reuse. I suggest that nesting in forests with high tree density may be an adap tion to avoid the Goshawk A. gentilis, which is the main predator on j uvenile Sparrowhawks.