Habitat structure and habitat use of European Golden Orioles (Oriolus o. oriolus, L. 1758) during breeding and wintering [Vergleich von habitatstruktur und habitatnutzung in brutgebiet und Winterareal des Europaischen Pirols (Oriolus o. oriolus, L. 1758)]

Abstract

Habitat structure and habitat use of European Golden Orioles were compared in breeding and wintering habitats of northwestern Germany and Zimbabwe. In 25 bird use plots per area, tree density, crown cover, vertical foliage distribution, maximal vegetation height and stratum of maximal vegetation density were measured as an analysis of vegetation structure. For habitat use, the height of trees used by the birds, the horizontal and vertical position of birds in the trees and behavioural parameters were observed. Woodlands in Zimbabwe are lower (14,2 vs 16 m maximal height of vegetation) and more open (573 trees/ha vs 865 trees/ha) than breeding habitats in Schleswig-Holstein and show differences in vertical vegetation structure. Both habitats show well developed vegetation structure and seasonality. In northwestern Germany the diversity of vertical foliage distribution is about 21% higher than in the plots of Zimbabwe, however in Africa the heterogeneity of tree distribution is 25% higher and the index of heterogeneity of crown cover is 29% above the data measured in the breeding habitats. The floral composition in both habitats is dominated by a few tree species. In respect to habitat use no niche shift could be documented between breeding and wintering areas as the birds prefer the outer crown area of trees of 13 - 14 m in height. European Golden Orioles can normally be found at about 85% of tree height, closely above the zone of maximum vegetation density.