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Central place foraging for eating versus feeding the young: Alternative patch-use by parents.
MARKMAN, SHAI1, PINSHOW, BERRY1, WRIGHT, JONATHAN2, KOTLER, BURT1, 1 2
ABSTRACT- Studies concerning central place foraging by parent birds ignored the spatial separation of food types used by parents for eating versus provisioning young, despite life-history implications for foraging strategies. Palestine sunbirds (Nectarinia osea) consume nectar and arthropods, but feed only arthropods to their young. This separation of food types allowed testing trade-offs in foraging effort between patches containing nectar for self-feeding versus patches with nectar for self-feeding plus arthropods for provisioning young. Parents were offered a patch containing sucrose solution with concentrations varying between 0.25-0.75 mol. On the other side of their territory they were offered a constant patch with a 0.25 mol sucrose solution feeder plus flightless flies feeder. Titration of sucrose concentration in the variable patch (food for self-feeding only) showed it had to be twice as concentrated as that of the constant patch (self-feeding and delivery) for parents to spend an equal amount of time foraging at both patches. The value to parents of the flies (food for self-feeding and delivery) in the constant patch was equivalent to 0.25 mol sucrose solution (self-feeding) in the variable patch to males, and 0.3046 mol to females. These sex differences reflect the fact that females mostly provisioning young in the nest, while males patrol more against predators. These results demonstrate for the first time alternative trade-offs in foraging effort between patches used for more than one form of life-history investment.
KEY WORDS: Nectarinia osea, PARENTAL CARE, LIFE HISTORY, PROVISIONING