Looking for something specific? Use our search engine!

Press Release

Press Release

Doctoral Thesis on Behavioural and Physiological Responses of Female Eiders Facing the Recovery of the White-Tailed Eagle

Bertille Mohring.
Bertille Mohring

M.Sc. Bertille Mohring’s doctoral thesis in Environmental and Marine Biology will be put forth for public defence at the Faculty of Science and Engineering at Åbo Akademi University.

The thesis is entitled Breeding during a predation regime shift: behavioural and physiological responses of female common eiders facing the recovery of their native predator.

The public defence of the doctoral thesis takes place on 14 December 2023, at 12PM in the Argentum auditorium, Aurum, Henrikinkatu 2, Turku. You can also attend the public defence of this doctoral thesis online.You can also attend the public defence of this doctoral thesis online. Professor Jon Brommer, University of Turku and Assistant Professor Suvi Ruuskanen, University of Jyväskylä, will serve as opponents, and Professor Kai Lindström, Åbo Akademi University, as custos.


Predation is a key environmental stressor and prey population persistence depends on the ability to cope with this selective force. Nevertheless, the extent to which direct killing versus indirect predation effects (‘fear’) shape prey phenotypes in the wild is still insufficiently understood. In my thesis, I investigated how the common eider Somateria mollissima, a key species of the Baltic Sea, adjusted its behaviour and physiology to cope with the strong recovery of white-tailed eagles Haliaeetus albicilla, their main native predator.

My thesis was based on a long-term monitoring of breeding female eiders in southwestern Finland subject to increasing white-tailed eagle predation. I studied risk-taking behaviour (flight initiation distance) and physiological proxies of energetic reproductive investment (baseline corticosterone) and parental effort (baseline prolactin). In line with theory, predicting reduced parental investment under elevated predation, increasing predation risk was associated with a reduction of risk-taking in incubating female eiders, and a physiologically mediated reduction of energetic reproductive investment. In contrast, the maintenance of high prolactin levels, correlated with increased parental effort, promoted hatching success under environmental constraints, including elevated predation risk.

The results of my thesis provide valuable insight into the short- and long-term responses of prey to a changing predation regime, highlighting that both plastic behavioural and physiological adjustments and selection shape prey coping strategies, but their relative importance depends on context. Seabirds are declining worldwide. By exploring the scope of behavioural and physiological responses of eiders in coping with increasing predation risk, my thesis provides crucial information for successful management of threatened seabirds and for assessing the resilience of their populations in the face of changing predation regimes. 



Bertille Mohring was born in 1995 in Versailles, France. She can be reached by email bertille.mohring@abo.fi.

The doctoral thesis can be read online through the Doria publication archive. 

Click here for a press photo of the doctoral student.