Perch availability and ground cover: factors that may constitute suitable hunting conditions for pale chanting goshawk families

Abstract

We investigated the impact of perch height and abundance, and the cover for prey, on the hunting tactics of perch-hunting pale chanting goshawks (Malierax canorus). Mhough pale chanting goshawks demonstrate a clear preference for perching on the highest available perches, the availability of perches is of more importance than height because these birds hunt almost exclusively from perches, move regularly between them, and an increased number of perches increases the area of habitat accessible for effective hunting. In Succulent Karoe, pale chanting goshawks occupied areas where perch density (16 natural and 122 artificial/25 hal was significantly higher than in unoccupied areas (8 natural and 12 artificial/25 hal. The high proportion of cover formed by natural perches (trees and shrubs; 36%) and the low proportion of open ground (42%) resulted in Closed Spekboomveld being unsuitable for pale chanting goshawks, relative to the adjacent Open Spekboomveld that supported goshawks by offering a less restricted view of the ground and prey (perch cover 18% and open ground 49%). In Karroid Broken Veld, the combination of perch availability (3 026/25 hal and open ground (62%) may provide the most suitable conditions for hunting rodent prey near cover or in the open. We suggest that such habitat may also provide a pathway, through fitness benefits gained, in the development of delayed dispersal and cooperative breeding in pale chanting goshawk families.

S. Afr.J. Zool. 1997,32(1)