Quantifying the pattern and magnitude of spatio-temporal variation in demography, and identifying underlying causes, is key to understanding population dynamics. Using long-term, spatially-explicit data from a small population of European Starlings (Sturnus vulgaris) on Fair Isle, Scotland, I quantified spatio-temporal variation in demography and investigated its underlying mechanisms. I objectively described the population’s physical structure and hence defined spatial clusters of nest sites at multiple spatial scales. I quantified spatio-temporal variation in reproductive success and survival, across clusters and years. I explicitly included multiple broods in these analyses, examining their effects on variation in reproductive success and pre-breeding survival. My results demonstrate substantial small-scale spatial variation in both reproductive success and adult survival, contesting the common assumption that demography will be spatially homogeneous at small scales within populations that lack obvious subdivision. The inclusion of second broods had a substantial effect on spatio-temporal variation in reproductive success, however, the pre-breeding survival of second-brood individuals was so low that ultimately they may not have a large effect on population dynamics. I quantified dispersal movements of colour-ringed individuals, demonstrating that individuals breed significantly closer to their natal site than expected under random settlement. Individuals that left their natal cluster to breed moved to less productive clusters more than expected, and the difference in productivity between natal and breeding clusters did not vary with the number of available nest sites in the breeding year. The absence of nest-site availability effect suggests such patterns are consistent with source-sink dynamics, rather than site-dependent population regulation. Finally, I quantified the effect of grassland availability on demographic variation, since reduction in grassland is postulated to be a major factor in starling decline across Europe. However, there was no significant effect of the proportion of grassland surrounding the nest site on reproductive success or subsequent survival.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:577666 |
| Date | January 2013 |
| Creators | Brickhill, Daisy |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=201726 |
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