For a decade, researchers have collected data on growth and survival rate of black-legged kittiwake chicks on SEAPOP’s key-site Anda in northern Norway each summer. By combining these data with information on chick diet and local weather conditions during the same periods, they now demonstrate that chick growth and survival rate at this site can best be explained by wind speed, wind direction and type of prey in the chick diet.

Seabird populations worldwide are in decline. The reasons for this are complex. It has, however, been shown that chick production can be an important driver of population change. Hence, it is important to understand which factors determine the growth rate and survival of the chicks, and thereby the total chick production. Reduced prey availability and increased external pressure of different kinds may, for example, force adult seabirds to prioritize their own body condition at the expense of chick production. Plainly spoken, the adults will have to eat the food they find themselves instead of feeding it to their chicks.

Populations of black-legged kittiwake are declining rapidly in large parts of the species’ distribution range. For a decade, researchers have studied how weather conditions and the composition of prey items in the chick diet affect reproduction in kittiwakes at Anda, one of SEAPOP’s key-sites. The results of the study, now published in a new article, show that growth and survival rate of the kittiwake chicks were affected by the type of prey they got.

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Extreme weather and altered prey availability makes it difficult for black-legged kittiwakes to keep their chicks alive through the rearing period.
Photo: Signe Christensen-Dalsgaard, NINA

The chicks grew faster if there was a large proportion of sandeel in their diet, a pattern that was especially pronounced for the youngest chick in 2-chick broods. The researchers also found that strong winds had a negative effect on chick growth rate. They believe that strong winds hampered the adult birds’ ability to catch prey, reducing the amount and quality of prey delivered to the chicks. Periods of strong southerly winds were associated with increased chick mortality. This is likely because parts of the colony are exposed to waves from the south, leading to nests being washed down when waves are high.

The study emphasizes the importance of identifying and protecting important feeding habitats for seabirds in ensuring recruitment to the seabird populations. This may prove increasingly important as climate change seems to cause more extreme weather and alter the composition of available prey in the ocean.

Contact person: Signe Christensen-Dalsgaard, NINA