TERRITORY AND NEST DEFENSE IN POLYANDROUS PALE CHANTING GOSHAWKS - DOCO-BREEDERS HELP

The behaviour of polyandrous and monogamous pale chanting goshawks Mel ierax canorus was investigated to determine if co-breeders, by defendi ng the territory and nest contents, helped to increase the fitness of polyandrous trios. Polyandrous trios consisted of a female and male br eeder, as well as a subordinate co-breeding male. Pale chanting goshaw k males performed most of the interspecific territorial maintenance du ties, as well as participating in aggressive intraspecific interaction s against other males on territory borders. Intraspecific territorial interactions were almost exclusively recorded in high-quality habitat, Karroid Broken Veld, and probably functioned in the defence of foragi ng habitat and potential mates. In this habitat, males of polyandrous families largely occupied exclusive sections of a territory. It is sug gested that the cost of defending territories in Karroid Broken Veld w as offset by the co-breeder's contribution to high-risk, intraspecific territorial defence. During the nestling period females of polyandrou s trios stayed at nesting sites for longer periods than did monogamous females and all males, enabling these females to guard the nest and a ct as sentinels. Predation of nestlings was recorded at the nests of m onogamous pairs, but not at those of polyandrous trios. Go-breeders di d not guard the nesting site but contributed directly to nest defence by either coming to the female's aid when solicited, or attacking pote ntial predators when present at the nesting site. Go-breeders may also have helped indirectly, through activities such as provisioning prey to females that relieved them of their hunting duties. We suggest that the female's nest guarding and the resulting lower nest predation may hold reproductive and fitness benefits for polyandrous breeders.