Bass Rock Breeding Success

The Bass Rock is home to an incredible spectacle. Each Spring, it experiences the return of one of the world’s largest colonies of Northern gannets (Morus bassanus). These large seabirds gather on the island in such vast numbers that, during the summer, the island appears bright white.

Gannets return to the island in March to establish territories and nest sites, and to build bonds with their chosen partner. Over the course of several months, pairs will endeavour to hatch and raise a chick, looking after it until it is old enough to fly and find food for itself. Gannet pairs raise only one chick a year, but its survival isn’t guaranteed. Eggs and very young chicks can be crushed or succumb early on to predation, human disturbance and the extreme conditions experienced on an exposed and rugged island such as Bass Rock. New or inexperienced pairs may be less likely to raise a chick successfully. Because of these factors, not every pair in a colony will successfully raise a chick each year.

Establishing breeding success (known as productivity) is an important aspect of monitoring a seabird colony. Pressures such as a lack of available food, changes to the environment and extreme weather events can mean that gannets are less successful at raising a chick. These pressure can be caused and exacerbated by human activities including overfishing, offshore developments and those amplifying climate change. Furthermore, after an outbreak of Highly Pathogenic Avian Influenza (HPAI) in 2022, when many adults died and there was almost complete breeding failure, the Bass Rock population declined by as much as 31%. This unprecedented decrease makes it more important than ever to monitor the population so that conservation actions can be developed effectively.

Unfortunately, monitoring gannet productivity comes with some significant challenges. Colonies can be expensive and challenging to access and the gannet breeding season lasts nearly six months. At many sites, this makes the traditional technique of visiting the site and monitoring it in person impractical. Fortunately, by using the Scottish Seabird Centre’s live webcams (which you can view online here or in our Visitor Centre’s Discovery Experience) in combination with trail cameras, monitoring of this important colony on Bass Rock can be carried out remotely.

To complete this essential research, The Scottish Seabird Centre worked in close collaboration with Edinburgh Napier University (Centre for Conservation and Restoration Science) and UK Centre for Ecology & Hydrology. We are very grateful to all the individuals and organisations involved for bringing their extensive expertise and commitment to this project.

Summary of Productivity Monitoring Results: 2025

The 2025 monitoring efforts on Bass Rock mark the beginning of concerted efforts to collect annual, robust and comparable productivity data on this colony. Six plots were selected in early Spring 2025, and two approaches—live controlled webcams and static photo trail cameras—were used to monitor breeding success of gannets. Data from the four webcam-monitored plots showed an average productivity of 0.53 chicks fledged per Apparently Occupied Nest (AON).

Productivity across the webcam plots was fairly consistent. In contrast, the two trail camera plots showed striking differences: one had high success, while the other had very low success. Continued annual monitoring using webcams and trail cameras will be essential to refine remote monitoring techniques and to determine whether the 2025 findings reflect long-term changes in the colony.

To find out more about how this assessment was completed and the methods and assumptions that underpin these results, please read the 2025 Bass Rock Productivity Report:

2025 BASS ROCK PRODUCTIVITY REPORT

The 2025 report and analysis of results was supported by the Scottish Marine Environmental Enhancement Fund (SMEEF).

Find out more

Discover more about how the Scottish Seabird Centre and our partners have been working together to conduct population counts of gannets on Bass Rock here.

Header image (c) Pete Ivin; Thumbnail image (c) Jamie McDermaid