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Effects of age on reproduction and chick rearing in bridled terns (Onychoprion anaethetus) at Penguin Island, Western Australia

Labbé, Aurélie (2017) Effects of age on reproduction and chick rearing in bridled terns (Onychoprion anaethetus) at Penguin Island, Western Australia. PhD thesis, Murdoch University.

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Effects of age on reproduction in seabirds have been widely documented and need to be taken into account when devising management strategies. The purpose of this research was to: 1) establish a general context by determining which age-related processes affect reproduction in seabirds; and 2) in a specific case of a population which has undergone exponential growth associated with changes in oceanic conditions and increased food supply, determine whether age has an effect on the reproduction of bridled terns Onychoprion anaethetus at the Penguin Island colony in Western Australia. To investigate the latter, I attempted to use a molecular method for aging bridled terns. To determine whether age affected breeding in bridled terns, I used two different approaches: one was based on relating the age of breeding pairs to several breeding variables using cross-sectional and longitudinal analyses, and one was based on determining whether there were differences in the diet fed to chicks by parents of different ages using faecal DNA meta-barcoding techniques. I found that effects of age on the reproduction of seabirds were wide-spread and that breeding experience and breeding senescence were the main processes driving these effects. I found that it was not possible to age bridled terns using skin collagen-bound pentosidine as a bio-marker, so I had to use banding information instead. There did not appear to be an effect of age on the post-laying breeding performance in bridled terns and there was no clear difference in the diet of chicks from younger and older parents. Such findings suggest that the only effect of age on reproduction in this species occurs pre-laying because younger birds did not lay eggs, and that the favourable environmental conditions in Western Australia and/or unidentified physiological attributes negate effects of aging post-laying. However, small sample sizes and possible bias in aging birds were major limitations. My research suggests that bridled terns may be differently impacted by aging compared to other seabird species.

Item Type: Thesis (PhD)
Murdoch Affiliation(s): School of Veterinary and Life Sciences
Supervisor(s): van Keulen, Mike, Calver, Michael and Dunlop, Nic
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