Arctic tern flyways and the changing Atlantic Ocean wind patterns

Migratory bird trajectories are the result of their own speed and direction in combination with wind speed and direction. Several studies have focused on the interplay between bird migration and general wind patterns, however, the majority of them did not take into account climate change and used a small number of individuals. By integrating tracking data from two populations of Arctic terns (n = 72) with ERA5 and Earth System Model (ESM) wind data, we were able to study the current conditions and the potential effects of climate change on them.The Svalbard birds experienced wind support values around 3 m/s with a relatively low variability, while the Dutch population experienced almost no wind support with a greater variability. Svalbard terns exhibited better adjustment of their flyways to daily and annually varying wind conditions, and responded to crosswinds by drifting over extended periods/regions (median Drift Ratio ± standard deviation: 0.51 ± 0.18) while the Dutch population mostly compensated (0 ± 0.31). We suggest that the Svalbard birds will be able to adapt their flyways to future Atlantic Ocean wind pattern changes, while we are uncertain whether the Dutch population can keep compensating for future changes or not.We examine the robustness of our results by using a selection of ESMs and by including metrics for several uncertainty sources (ESMs, wind variability, tracking method etc.). This study highlights the importance of wind as a flyway-shaping factor and points out the possibility for different responses to wind by different populations of the same species, in different Ocean regions and seasons

Nest defence behaviour is similar between pair members but only male behaviour predicts nest survival in barnacle geese

Behavioural patterns often differ consistently across individuals and are linked to fitness. In species with biparental care, the defence behaviour of both parents can affect reproductive success through offspring survival. In addition to the intensity of defence behaviour by both pair members, the similarity in this behaviour among parents may affect offspring survival. However, few studies have investigated the relative impact of both the intensity and similarity of defence behaviour. Here, we examined nest defence behaviour of males and females during the incubation stage in an Arctic population of barnacle geese Branta leucopsis. We calculated the repeatability of defence behaviour to test whether this behaviour is consistent within individuals and investigated how it is associated with age. In addition, we investigated how daily survival rate (DSR) of the nests until hatching is associated with nest defence behaviour and age of the parents, as well as the effect of parent similarity in nest defence behaviour as an emergent trait of the pair bond. Both male and female defence behaviour were highly repeatable. The ages of both partners within breeding pairs were positively related, but age was only significantly associated with defence behaviour in females. Further, we found high similarity in defence behaviour within breeding pairs, but the similarity and intensity of defence behaviour within breeding pairs did not predict DSR. Finally, male defence behaviour positively predicted DSR, but female defence behaviour and male and female age did not. Our results suggest that nest protection is adaptive in males but behavioural similarity of pair members does not enhance nest survival, indicating behavioural similarity itself is not adaptive but rather a by-product of different effects