In a constantly changing environment, the ability to adapt to the changes is essential. Recent Norwegian research shows that the black-legged kittiwake is surprisingly flexible when it comes to finding food for itself and its chicks. The ability to adapt makes this small gull robust to changes in the marine environment – that is, if it has access to suitable foraging habitats near the colonies.
Overfishing, climate change, pollution and other anthropogenic processes cause worldwide changes to marine environments. These changes may have substantial effects on species richness and food chains, and there is increasing concern about how top predators, such as seabirds, might adapt to the changes. To be able to implement long-term conservation efforts for seabirds, we need to understand how seabird populations respond to variations in environmental conditions and to what extent they are able to adjust their behaviour to compensate for a changing food availability.
Using multiannual data from two Norwegian kittiwake colonies with very different oceanographic conditions, researchers have now investigated how the foraging behaviour of breeding kittiwakes is influenced by the distribution of feeding habitats near the colony, combined with dominating weather conditions and body condition of the adults. The researchers used GPS-loggers and saltwater immersion switches to map where the kittiwakes went to find food for their chicks and what their behaviour was like in the different areas.
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The study shows that the productive zone along the Norwegian shelf break, where the Norwegian coastal current meets the North-Atlantic current, is an important foraging area for birds from both colonies. In fact, this area is so important that birds from one of the colonies chose to fly more than 300 km to feed there. However, the distance to the Norwegian shelf break determined which factors drove the kittiwakes to forage there. Among the kittiwakes breeding far from the shelf break, primarily individuals with low body weight relative to body size chose to fly to the shelf break to forage, probably in order to enhance their body condition. For birds breeding close to the shelf break, however, the choice of feeding habitat was closely related to access to prey items at different times of the day and under different weather conditions. In other words, the birds adapted to the diurnal rhythm of their prey in order to collect as much food as possible. The study shows that black-legged kittiwakes can be flexible to changes in the marine environment, but the flexibility depends on access to feeding areas near the colonies.
Contact person: Signe Christensen-Dalsgaard, NINA