From population to individual: colony dynamics and structure in time and space of a highly social seabird

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Garrett, Lucy Jane Helen ORCID: https://orcid.org/0000-0002-4957-3753 (2020). From population to individual: colony dynamics and structure in time and space of a highly social seabird. University of Birmingham. Ph.D.

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Abstract

Understanding why populations change in size and distribution can help us assess a species’ vulnerability to future environmental change (e.g. climate warming) and their conservation status. This thesis focuses on a population of sooty terns, a small seabird, that breed in huge numbers on Ascension Island in the South Atlantic. By combining long-term data on population size and breeding movements with genetic relatedness and chick survival, we explore the effects of environmental and social processes that may underlie population trends. We found evidence for a shift in population size between two breeding sites on the island. Despite high population genetic diversity and low levels of relatedness we found fine-scale genetic structure between neighbours. There was evidence that birds breeding earlier were genetically different to those breeding over one month later. Chick sociality was a key factor influencing daily survival together with the use of habitat cover, both of which are likely responses to predation risk. The shift in population size between breeding sites suggests instability in habitat quality, with potential declines in breeding success driving breeder movements. Overall our findings suggest differences in animal behaviour can have significant effects on population ecology, genetic structure, breeding timing and breeding outcomes.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):