Journal article
Factors affecting the foraging distance and duration of a colonial bird, the sociable weaver, in a semi-arid environment

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Publication Details
Author list: Kyle John Lloyd, Res Altwegg, Claire Doutrelant, Rita Covas
Publisher: Wiley: 12 months
Publication year: 2018
Journal: African Journal of Ecology
Volume number: 56
Start page: 659
End page: 663
Total number of pages: 5
ISSN: 0141-6707
eISSN: 1365-2028

Coloniality has clear foraging benefits such as reducing the probabil-ity of being predated, enhancing the probability of finding food and allowing for easier estimation of habitat quality (Danchin & Wagner, 1997). However, living in a colony can also have potential foraging-related costs, because all of the birds in the colony are conspecifics with similar food requirements (Wittenberger & Hunt, 1985). Individ-uals living in larger colonies may deplete local resources and have to travel farther and for a longer duration in search of food than those living in smaller colonies (Brown & Brown, 1996). We examined this idea for the sociable weaver (Philetairus socius), a facultative colonial cooperative breeder that builds large communal nests (Maclean, 1973a). An effect of colony size might be expected because previous
studies have found that fewer eggs and nestlings successfully hatch and fledge in large colonies (Altwegg, Doutrelant, Anderson, Spottis-woode, & Covas, 2014), which may be due to the high levels of intraspecific competition for resources (Covas, du Plessis, & Doutre-lant, 2008). Foraging farther away from the colony for longer periods of time may also reduce adult survival by increasing the chances of being seen and caught by a predator, as a greater distance needs to be covered to reach the safety of the colony. The hypothesis that larger colonies forage farther and for a longer time than smaller colo-nies was investigated by tracking the foraging paths of flocks from
eight colonies of varying sizes. In this study, we also tested the effects of covariables known to affect the foraging behaviour of birds, namely landscape structure and weather (du Plessis, Martin, Hockey, Cunningham, & Ridley, 2012; Turcotte & Desrochers, 2003). In addition, the foraging behaviour of sociable weavers in a more mesic region (431 mm/year) of the Kalahari is described for the first time (see Maclean, 1973b for arid regions, 226 mm/year).

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