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Bachelor thesis examination

Science and Information Technology

At the brink of extinction - factors affecting chick survival in a critically endangered shorebird

Examination
Date
18 Mar 2021
Time
13:00 - 13:25
Location
Zoom

Participants
Student Malin Johansson
Good to know
For Zoom link to the examination contact Lotta Kvarnemo.

Abstract

Populations of shorebirds are rapidly declining, and the Southern Dunlin Calidris alpina schinzii is one of the most endangered species in the Baltic region. Due to destruction of their natural habitat, the metapopulations of the Southern Dunlin have become small, isolated, and vulnerable. Given the findings from earlier studies, the probability of local recruitment (returning to the population after migration and wintering) is mainly influenced by chick survival during the first three weeks – from hatching until fledging. In this study, I therefore investigated what contributes to the success of a brood to produce fledglings, using a long-term dataset from the metapopulation of Southern Dunlins breeding at the Swedish west coast. I examined the risk of predation (here estimated as the predation rate on nests); the annual effect, testing whether yearly brood survival decreases over time (as would be expected due to increased inbreeding); the seasonal effect (measured as birth date); and the size of the breeding area. The aim was further to evaluate the relative effects of these factors on brood survival. Interestingly, a non-significant tendency for an increase in brood survival can be seen in the later years. A possible explanation might be that only the fittest individuals manage to produce a brood that later results in fledglings. Brood survival was also not significantly affected by any of the other variables. This might suggest that another way of assessing predation on chicks needs to be done in future studies. My results provide valuable knowledge on how to proceed the investigations and thereby forming better conservation plans in the future.