Egg production in the thick-billed murre (Uria lomvia) and razorbill (Alca torda) - a life-history perspective
A key tenet of life-history theory is that costs of reproduction lead to physiological and evolutionary trade-offs among fitness components. Although avian egg production was a key topic in the development of life-history theory, the significance of egg production costs within the life histories of...
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| Format: | Thesis |
| Language: | English |
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Memorial University of Newfoundland
2000
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| Online Access: | https://research.library.mun.ca/1332/ https://research.library.mun.ca/1332/1/Hipfner_JMark.pdf https://research.library.mun.ca/1332/3/Hipfner_JMark.pdf |
| Summary: | A key tenet of life-history theory is that costs of reproduction lead to physiological and evolutionary trade-offs among fitness components. Although avian egg production was a key topic in the development of life-history theory, the significance of egg production costs within the life histories of birds remains poorly understood. Two aspects of egg production that have received considerable attention are variation among females in their capacity to renest following clutch loss, and variation in the size of egg they lay. I examined these aspects of egg production in two pelagic seabirds, Thick- billed Murres Uria lomvia and Razorbills Alca torda. It is generally thought that egg production costs are relatively low in pelagic seabirds that lay single-egg clutches, but age- and date-specific patterns in renesting capacity and egg size suggest that significant constraints on egg production operate in these birds. -- The proportion of Thick-billed Murres that renests following egg loss declines with the date of loss. However, early-laying females that had their eggs removed continued to renest until late in the laying period. First and replacement eggs were similar in crude composition, but replacement eggs had low protein content. Despite this, replacement eggs were no less likely to hatch than were first eggs, and chicks from replacement eggs were no less likely to survive to nest departure, and to recruitment age (4-5 years). I conclude that variation in the egg-production capacity of females that lose their eggs early and late (probably age/experience effects) drives the seasonal declines in renesting rates. Capable females will relay until late in the laying period because, for these birds, the potential fitness payoff from a replacement egg is similar to that from a first egg. It remains to be determined whether there are survival costs associated with the production of replacement eggs for female Thick-billed Murres. -- Thick-billed Murre eggs vary considerably in size, and egg size affects offspring ... |
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