New method for mapping the swimming migration in auks

Common guillemots, Brünnich’s guillemots and razorbills undertake a swimming migration with their chicks after leaving the colonies. Their migration speed, distance and direction have been largely unknown and difficult to determine. By comparing temperature data from geolocators attached to adult common guillemots with remotely-measured temperature gradients measured in the Barents Sea, a model has been developed for mapping their initial movement from colonies that takes place in a very vulnerable period of their life cycle.

Adult common guillemot with chickThe common guillemot chicks jump from the ledges of the breeding colonies long before they are able to fly. The lucky ones land in the water and can start the swimming migration away from the colony, normally acompanied by their fathers. Photo: Tone Kristin Reiertsen

A perilous journey

For several auk species, the first two months after departure from the breeding colony are a critical period. The chick jumps from the ledge before it is able to fly, and one of the parents accompanies it on a swimming migration away from the colony towards a favourable area for the chick to grow to independence. While he chicks need protection and help to find food, the adults also moult their flight feathers after reaching the nursing area for the chicks, making them flightless for a period of time. Despite the birds’ vulnerability to natural and man-made threats in this period, we know very little about where and how this migration takes place.

Alternative use of technology

Geolocators, also known as light loggers, which in recent years have provided new insight into bird migration, cannot reveal positions in periods of midnight sun and around the equinoxes in spring and autumn. Seabirds breeding in the Arctic undertake the post-breeding migration away from the colonies between the end of July and mid-September – i.e. in an unfavourable period for the use of light loggers. But light loggers may also measure other parameters, such as pressure and temperature. In addition, many models have a wet/dry sensor, indicating whether the logger is in the water or in the air. In a recent study, researchers from the Norwegian institute for nature management (NINA) and the Norwegian Polar Institute (NPI) have used data from SEAPOP and SEATRACK to develop a model that can shed light on the swimming migration of the large auks. The model uses temperature data from light loggers and sea surface temperature data from satellites, and the method was recently presented in NINA’s report series.

The report is available in Norwegian (with English summary):

 

Useful tool for management

The method was tested on common guillemots migrating from Bjørnøya to the southeast part of the Barents Sea in 2011, 2012 and 2015, and the average migration distances in these years were estimated to 470 km, 580 km and 522 km, respectively. The average migration speed was 37 km/day, and data from dive loggers revealed that the common guillemot chicks are dependent on help from their fathers to find food for about 60 days after departure from the colony. The development of this method allows us to improve our knowledge about the swimming migration of auks from a large number of colonies, and it enhances the ability of environmental managers to reach the right decisions for protecting our seabird populations and the habitats upon which they are dependent during this very vulnerable stage of their life cycle.

 

Contact person: Kjell Einar Erikstad, NINA