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dc.contributor.advisorCresswell, Will
dc.contributor.authorCox, Daniel T. C.
dc.description.abstractSeasonality influences life history through its effect on the availability of essential resources, with birds timing breeding to occur during peak food availability. Due to density-dependence, investment in breeding is determined largely by the seasonality of food availability, with an increased investment being traded-off against adult survival. A bird’s mass acts as an index of a species’ foraging environment, because a bird bases its foraging decisions on a trade-off between the risk of predation and the risk of starvation. Under constant predation risk a bird increases its mass as insurance against increased foraging unpredictability. In tropical savannahs day length and temperature remains relatively constant, and there is not a season of increased density-dependent mortality which acts across all species. Thus species have evolved a broad range of life history traits under the same environmental conditions, although how a species experiences seasonality depends largely on its foraging niche. This thesis shows that most savannah species varied their mass across the year, having a reduced mass in the non-breeding season which suggests that foraging remained predictable. Independent of gonad or egg growth they then increased their mass as they started to breed, with the timing of breeding coinciding with peak food availability. Across species in the same foraging niche mass acts as an index of breeding investment, with females increasing their mass more than males. While across species in different foraging niches an increased mass response was associated with higher adult survival, probably because breeding strategy and subsequently adult survival are governed by food limitation. This thesis shows that birds adaptively manage their mass during breeding and that mass is not a result of energetic stress, thus under constant predation risk a bird’s mass is a result of foraging predictability as a function of competition for available food and investment in breeding.en_US
dc.publisherUniversity of St Andrews
dc.rightsCreative Commons Attribution-NoDerivs 3.0 Unported
dc.subjectFood limitationen_US
dc.subjectInterrupted foragingen_US
dc.subjectTropical birdsen_US
dc.subjectMass-dependent predationen_US
dc.subjectBreeding indicatorsen_US
dc.subjectAdult survivalen_US
dc.subjectBrood patchesen_US
dc.subject.lcshBirds--Africa, West--Breedingen_US
dc.subject.lcshBirds--Africa, West--Seasonal variationsen_US
dc.subject.lcshBirds--Africa, West--Weighten_US
dc.subject.lcshBirds--Africa, West--Fooden_US
dc.titleSeasonal mass variation as a life history trait in West African savannah birdsen_US
dc.contributor.sponsorLeventis Conservation Foundationen_US
dc.type.qualificationnamePhD Doctor of Philosophyen_US
dc.publisher.institutionThe University of St Andrewsen_US
dc.publisher.departmentA. P. Leventis Ornithological Research Instituteen_US

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Creative Commons Attribution-NoDerivs 3.0 Unported
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