Foraging and territorial behaviour of male Cape and Gurney's sugarbirds (Promerops cafer and P. gurneyi)
Foraging and territorial behaviour of Cape and Gurney's sugarbirds were studied in the Western Cape and eastern Free State of South Africa, respectively. Cape sugarbirds spent most of their time in territory defence and resting at all times of the day - both at mid breeding season and at the end of the breeding season - and only about ten percent of their time foraging. Cape sugarbirds may feed in the morning to replenish energy deficits and water imbalances experienced at night, and then maintain a high feeding rate at midday to maximize energy gain when nectar energy availability is greatest. Gurney's sugarbirds, by contrast, showed little variation in the amount of time spent feeding on nectar throughout the day. More dispersed or lower availability of food may have constrained vocal activity in Gurney's sugarbirds, which spent most of their time throughout the day perching silently on the tops of trees. In Cape sugarbirds, feeding preferences for particular Protea species changed in relation to their flowering seasons, and reduced inflorescence availability during the breeding season is related to increased perching and decreased territory defence at midday.