We haven’t been able to go to Slettnes during the last breeding season in 2020 and 2021, hence the paucity of blog posts here. However, there is some news to report: our paper on the dramatic decline of Arctic Skua numbers at Slettnes has been published in Bird Study!
The first year that we worked in Slettnes, 2014, was a good year for the Arctic Skuas. Losses due to predation were few, food was abundant, and consequently, many pairs managed to raise chicks. Since then, almost no chicks fledged from the Slettnes colony, and the number of breeding pairs dwindled.
In our paper, we collated virtually all data that we collected during 2014-2019: nest counts, clutch and egg sizes, adult body mass, daily nest survival rates, annual apparent survival rates of adults, levels of aggressiveness in nest defense, the time spent at sea (from the geolocator wet/dry sensor), number of adults at the territory, fox sightings, and camera trap photos. We combined our data with data collected during 1997-1998 by Kirstin Janssen (Arctic University of Norway, Tromso). During 1997-1998, Kirstin found more than 175 nests per year and estimated the colony to hold about 250 breeding pairs. Some 20 years later, this number has halved… and I fear that numbers will have gone further down in 2020-2021.
In the paper, we argue that the decline is likely due to a combination of low food abundance and increased predation by Red Fox. Nowadays, even in years with high food abundance, Arctic Skuas at Slettnes may not be able to reproduce due to the high predation pressure.
You can find and read the paper here (open access).