DOI: 10.5061/dryad.jm63xsjk2
title: High-resolution images of 2023's bird cliffs at Skúgvoy, Faroe Islands

description: 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.
description: # High-resolution images of 2023's bird cliffs at Skúgvoy, Faroe
 Islands
 [https://doi.org/10.5061/dryad.jm63xsjk2](https://doi.org/10.5061/dryad.jm63xsjk2) #### Description of the data and file structure High-resolution images of the Common Guillemot cliffs numbered 1–44 are provided here. We counted all colony-nesting seabirds from a boat over three days of sailing. The west coast, spanning 7.4 km, was divided into 44 smaller delineated segments (Supplementary Fig. 1). This numbering system originated from the original complete survey of Common Guillemots in Dyck and Meltofte (1975). Thus, the number of breeding pairs on each cliff face is directly comparable to that of this previous census, assuming similar limitations and sampling biases. Moreover, all cliff faces were photographed from the boat using a Canon Full frame R5 and RF 100-500mm objective. Between 20-50 pictures were taken of each cliff face, which were then merged into a single image using Photoshop. We used these images to count the Guillemots and Kittiwakes, which nest exposed on the vertical cliffs. Supplementary Data 1 comprises all **1-44.jpg** and "**Stone_side1-2.jpg**". Supplementary Data 2 comprises "**høvdin from boat.jpg**", "**Høvdin top-down 0800.jpg**", and "**høvdin top-down 1500.jpg**". Supplementary Data 1. High-resolution images of each bird cliff section. Yellow lines mark the boundaries of the bird colonies assigned to each cliff section. Supplementary Data 2. High-resolution images of the cliff section 3, viewed from the sea surface and top-down from land. The cliff was photographed from above the 4/7 at 3:00 PM and on 11/7 at 8:00 AM. The same cliffs were photographed from a boat on 5/7 at 10:00 AM. The yellow lines mark the sections of the cliff that were visible in the photos taken from above.