Black guillemot surveys on Vigur and Æðey

In the first two weeks of May, Náttúrustofa Vestfjarða completed its third annual survey of the black guillemot (Cepphus grylle) colony on Vigur Island. This year, the island of Æðey was also added to this monitoring program, which commenced in 2022.

A total of four counts on Vigur, and two counts on Æðey, were completed. During the pre-egg-laying period, black guillemots gather closely at their breeding grounds at dusk and dawn and engage in social activities with other members of the colony. The display of hundreds of whistling, diving, chasing, and splashing guillemots is remarkable to behold and provides an opportune occasion for counting.

Vigur continues to hold what is likely the biggest breeding colony of black guillemots in Iceland, with a maximum of 779 pairs counted this year. While this number has slightly decreased from the previous year (835), this could be due to natural variation in the attendance of the birds, as their presence is known to change based on weather, timing of tides, the time of sunrise and sunset, and so on. Slight yearly fluctuations are expected in this long-term monitoring program. Over multiple years, however, it will be revealed if this population is stable, increasing, or declining.

Æðey also revealed a significant number of black guillemots, with around 667 pairs. The most recently published numbers regarding the breeding population for this island date back to the year 2000, with an estimated 500 pairs. It goes without saying that Ísafjarðardjúp is extremely important for black guillemots in Iceland, hosting these two islands with large breeding populations. This species is listed as endangered in Iceland due to significant declines around the country over the past decades.

We thank the residents of Vigur Island (Gísli Jónsson, Felicity Aston, and Þráinn Freyr) and Æðey (Alexíus Jónasson) for welcoming us to their islands to conduct these counts.

– Ingrid Bobeková