Otomyine rodent refuge habitat: does it represent habitat quality for palechanting-goshawk families?

The refuge habitat of the dominant rodent prey of family-living pale chanti ng-goshawks (Melierax canorus) was examined in the Little Karoo, South Afri ca. The density of 76-150-cm high shrubs accounted for 60% of the variation in the densities of the stick lodges of the dominant prey, Otomys unisulca tus. Densities of heuweltjies (raised soil mounds) accounted for 56% of the variation in the density of Parotomys brantsii warrens. Although young and non-breeding birds were found in all occupied vegetation types at the stud y site, attention was focused on Karroid Broken Veld since co-breeders were only found there. Karroid Broken Veld had heuweltjies and tall shrubs that were associated with both otomyines unlike other vegetation types that pre dominantly possessed only one of these characteristics. In this vegetation type, the high otomyine biomass (105 kg/km(2)) in some years and the abilit y to exploit two otomyine populations provided the chanting-goshawks with p rey choice and high energy returns. If the habitat structure that provides high-density refuge for two otomyines is unique to the study site, the repr oductive fitness benefits to resident pale chanting-goshawks may have been pivotal in the evolution of families in this population.