Epsilon Archive for Student Projects

Abstract

In this study I examine the habitat, breeding and diet preferences of two tern species (Sterna hirundo and Sterna paradisaea) in inland lakes in Sweden. Previous work has shown that Northern Pike (Esox lucius) can induce a dwarf ecotype of European Whitefish (Coregonus lavaretus), a potentially valuable food resource for piscivorous birds. Here I investigate if pike presence or absence in north western Swedish lakes has is linked to habitat use and diet of terns. Through visual surveys of 54 lakes, the capture and measurement of tern chicks, and the collection of faeces for metabarcoding analysis in summer 2024, I was able to demonstrate statistically significant preference of terns for lakes with pike. Metabarcoding analysis of the faecal samples revealed European Perch (Perca fluviatilis) with a fraction of 65 % as most important and whitefish (25 %) as second most important component of fish-diet in terns. Different proportions of whitefish in relation to pike absence or presence could not be identified. This also applies for tern chick condition, which I could not thoroughly assess due to data limitation. In conclusion, I was able to identify links between pike presence and tern habitat use. However, further studies are needed to better understand this ecological relationship.