Incubation behaviour of Arctic (Sterna paradisaea) and Antarctic (Sterna vittata) terns under disturbance by humans and predators

The activity of people increased worldwide and has become an important source of disturbance to nesting birds even in a pristine environment of the polar regions. In this study, we focused on the correlation between disturbances and incubation behaviour of two Sterna species. By video surveillance of nests on low-disturbance and high-disturbance sites we evaluated (i) whether the incubation behaviour of Arctic terns Sterna paradisaea in Svalbard differed between various levels of mostly anthropogenic (passing people) disturbances and (ii) whether the incubation behaviour of Antarctic terns Sterna vittata on the Antarctic Peninsula differed between various levels of mostly natural (predators) disturbances. We analysed whole-day continuous recordings (median length > 24 h) of 72 nests from four study sites. Incubation behaviour at high-disturbance sites was characterized by lower nest attentiveness, shorter on-bouts, and recurrent interruptions, whilst off-bout length remained mostly unchanged. The total time spent sleeping and average sleep-bout length were shorter, whilst the frequency of visual inspection of the surroundings was higher at high-disturbance sites. In all, the responses of incubating terns to human disturbance did not exceed those induced by native predators. The behavioural responses, as measured by the direction and size of effects, were remarkably consistent for both species, representing the two polar regions with different natural predation risks as well as a different history of human impacts. Unless there are specific long-term costs associated with human disturbance that we cannot evaluate here, the coexistence of people and breeding terns might be sustainable even in the polar regions.

Automated summary

This study examined the correlation between disturbances and incubation behavior of two Sterna species. The results showed that the responses of incubating terns to human disturbances were similar to those induced by native predators. This suggests that the coexistence of people and breeding terns in the polar regions may be sustainable.