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High-resolution images of 2023's bird cliffs at Skúgvoy, Faroe Islands

Olsen, Ivan; Hammer, Sjúrður1; Dinesen, Lars2; Sonne, Jesper2

Research facility: University of Copenhagen
Published Dec 19, 2025 on Dryad. https://doi.org/10.5061/dryad.jm63xsjk2

Data files

Dec 19, 2025 version files 3.40 GB

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Abstract

Since 1961, periodic bird censuses have been conducted on Skúgvoy (Faroe Islands) at approximately twenty-year intervals. This census examines the population trends of breeding birds, encompassing all bird species on the island, marking the fourth in a series within a timeframe of 62 years. The census, which includes both seabirds and inland birds and compares results over such a long period, is unique compared to other Faroese islands. The counting of inland birds has been carried out by mapping breeding territories, with colony-breeding seabirds counted individually on cliff ledges from the sea surface. We aimed to contribute to the historical bird censuses, providing long-term quantitative evidence for the species’ population dynamics. Moreover, we discuss the possible explanation for the decline of seabirds in the Faroes by directly comparing the population trends for seabirds versus terrestrial birds. We divided Skúgvoy's breeding birds into four groups depending on their foraging preferences: Marine (seabirds dependent on marine food resources), Semi-marine (seabirds partially dependent on marine food resources), Terrestrial (not dependent on marine food resources), and Passerines (insectivorous and granivorous species). Our results show minor fluctuations in terrestrial species compared to significant declines in all seabird species. This decline has not stabilized but rather accelerated since the last complete bird census in 2001, particularly among colony-breeding seabirds.