We study the stress factors and how stress functions in Barn Owls. In addition to allowing us to closely study the health of these owl populations, this gives us precise measuring tools to improve the conservation practices for this species.

1/4 Barn Owls, like all living creatures, are stressed when confronted with certain situations. We look to understand what factors create stress for Barn Owls. Lukas Linder © Swiss Ornithological Institute

2/4 In order to measure at what point owls feel stress, we take blood samples from the owls using a glass capillary tube in order to collect several microliters of blood. © Jeremy Bierer

3/4 We take these blood samples back to the lab to measure their levels of corticosterone, the stress hormone in birds. Félix Imhof © UNIL

4/4 In Switzerland, Barn Owls live naturally close to human beings. Nevertheless, our studies have shown that owls are less stressed when their nestbox is installed in an undisturbed area. © Jeremy Bierer

Stress hormone

Corticosterone is the hormone that regulates the stress response in birds. In humans, this role is played by cortisol. In owls, a situation that causes stress might be a lack of food, for example, or unsuitable weather conditions, the attack of a predator, or even a pathogen.

A powerful hormone response improves the animal’s chance of survival

We study the genetic origins and the physiological functioning of this stress response. We have also discovered that the rate of corticosterone in adult Barn Owls in a stress situation correlates to their survival. In other words, in a stressful situation, the higher the owl’s level of corticosterone, the better its chances for survival.

Nestlings prefer calm

By studying these hormone levels, but also by monitoring owlet growth and survival rates, we study the ways in which human activities near a nestbox (proximity of homes or cattle, and the type of crops grown in the surrounding area) can stress the young owls. Our results indicate that various activities have an effect on the nestlings. A heterogeneous agricultural setting around a nestbox seems to boost the quality and quantity of owlets. However, an increased human presence within a 20 m perimeter of a nestbox seems to be harmful to the health of the nestlings but does not impact their number. These results indicate that, despite the fact that Barn Owls seem to be a species that is used to humans, it is better to install an artificial nestbox in a calm corner compared to a location where humans may frequently pass close by.