Territoriality and breeding success in Gurney's sugarbird, Promerops gurneyi
Territory size and quality were determined for Gurney's sugarbirds in Qwaqwa National Park, northeastern Free State, South Africa. Changes in territory size of Gurney's sugarbirds during the six-month season reflect increases in numbers of territorial birds and inflorescences at mid breeding season, and declines in both at the end of the breeding season. Only 25 % of pairs laid eggs, and mating appears to have been constrained by low nectar and arthropod energy availability, and the costs associated with the defence of large territories. Reproductive success was directly related to arthropod availability on territories, with pairs not even appearing to attempt breeding if this is low. Males with longer tails and wider sixth primary feather bulges defended larger territories, indicating that ornament size and displays of Gurney's sugarbirds may be important in territory maintenance.