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Kittiwalkers. 2024, Episode 1: Citizen Science in Action!

Writer's picture: Delphin RuchéDelphin Ruché

Updated: Dec 17, 2024

The Kittiwalkers are citizen scientists, sentinels and whistleblowers. In this post, we are focusing on citizen science and reporting about our achievements as 2024 is coming to an end. We will write about our contributions as sentinels and whistleblowers in a next post.


Two Kittiwalkers - citizen scientists - in tromsø monitoring kittiwake hotels.

First, who are the Kittiwalkers?


The Kittiwalkers is a grassroot movement led by the nonprofit Rissa Citizen Science and run by volunteers who believe that coexisting with kittiwakes in Tromsø is possible. The Kittiwalkers act as sentinels, informing building owners, preventing illegal destruction of kittiwake nests, and reporting infractions to the authorities. They call for help when they spot a kitiwake stuck in a net or injured by spikes. They rescue chicks that fall off their nest. They collaborate closely with scientists, Tromsø kommune, architects, and artists involved in the Urbanekrykkje project, all united by a shared goal: developing solutions for harmonious coexistence with kittiwakes in Tromsø.


"Based on a business-as-usual scenario, the median time to extinction of the Norwegian colonies of kittiwakes is 10 to 48 years." Sandvik et al. 2014 (Climate Research journal)

Two Kittiwalkers in Tromsø are surveying kittiwake nests.

Mapping every nest in Tromsø city center


Why is mapping kittiwake nests so important?


For one, it is the only way to know how many kittiwakes are in Tromsø during the breedging season, and how the demographics changes. Thanks to these counts, we know for example that the population of kittiwakes in Tromsø has tripled between 2020 and 2023. In 2024, the population still increased. If you live in Tromsø, you might have the impression that kittiwakes are doing well. But kittiwakes are declining dramatically in mainland Norway, and more of the survivors seek refuge in the city.


It is equally important to understand how kittiwakes respond to the continuous destruction of their nests and colonies in the city. When a building that hosts a colony is covered with bird deterrents, the colony splits in smaller units and kittiwakes move to neighboring buildings. Sometimes to buildings that were not used by kittiwakes before. This spreads hostility toward kittiwakes. By meticulously mapping each nest, the Kittiwalkers keep track of these destructions and the resulting displacements. These observations provide insight into what may occur the next time a colony is intentionally destroyed. They also help develop solutions to attract displaced kittiwakes to the "kittiwake hotels", these structures specifically designed to prevent their dispersion to neighboring buildings.


A group of voluntees called Kittiwalkers are counting kittiwakes on a building in Tromsø.

The study area


The Kittiwalkers' study area covers the central part of Tromsø city center. More kittiwakes are found outside this study area, which corresponds to what can be realistically monitored by volunteers, on foot, frequently, and without interruption from March to September. Ornithologists at the Norwegian Institute for Nature Research (NINA) monitor the nests outside the Kittiwalkers' study area. Combined, all these observations offer a comprehensive overview of the situation on Tromsøya.


In the study area, the Kittiwalkers have mapped all the nests that are visible from the street. The map had to be updated several times at the beginning of the breeding season, until the 13th of June after which no new nest was found. At that point, every unit (from a single nest to over a 100-nest colony) was associated with a name and a number.


The 2024 Kittiwalkerss'map for Tromsø city center.

Anyone can become a Kittiwaker!


Two training sessions of 2 hours are all it takes to master the methods, after which volunteers are generally regarded as – and feel like – reliable citizen scientists. The most dedicated volunteers spend several hours per week contributing, while others prefer a more occasional approach, mapping one or two nests on their way to work for example. Whatever works! Every contribution counts. Collectively, the Kittiwalkers produce more data than any hired scientist could generate alone.


In addition to the nests on buildings, the Kittiwalkers survey the four kittiwake hotels in Muséparken . There, for every nest, they note if it is empty or in use, and the number of chicks (1, 2 or 3). It takes less than 5 minutes to map one hotel. Many adult kittiwakes are ringed on these hotels. If one of them is spotted, the Kittiwalkers read the 3-digit code that is visible on the ring from a distance. These observations provide valuable insights into the survival, reproductive success, and movements of the kittiwakes in town.


A volunteer part of the Kittiwalkers is monitoring kittiwake hotels in Tromsø.

Preliminary results


Some exciting figures now! Let's start with the number of breeding pairs in the study area.


On the figure below, the dotted lines represent the number of observed adult kittiwakes. The solid lines show the number of breeding pairs (or AON, for "Apparently Occuped Nests"). DoY (Day of the Year) 100, 150, 200 and 250 correspond respectively to the 9th of April, the 29th of May, the 18th of July and the 6th of September. In 2023, the counts started late in the season, but early enough to see that the population growth observed between 2020 and 2023 has continued. At the peak of the 2024 breeding season (mid July, DoY 190), the Kittiwalkers counted around 300 nests or breeding pairs. There is more to say about this figure, but we want to keep this post short! Feel free to write in the comments below or contact us with questions.

Hoa many kittiwakes were in Tromsø in 2023 and 2024.

Figure by Dr. Macfarlane.


The next figure about the kittiwake hotels is also very interesting!


It shows the number of occupied nests on the four kittiwake hotels in Muséparken. Here, it's useful to know that hotels 1, 2 and 3 were set up in 2023, and have been used by kittiwakes for two consecutive seasons, while hotel 4 was put in in 2024 before the start of the breeding season. Also, hotels 1 and 2 are identical, while 3 and 4 have a unique design.


This figure helps understand what makes a kittiwake hotel attractive to kittiwakes. In Tromsø, we are still in the early stage of developing solutions for coexisting with kittiwakes, and there is much to learn. Thanks to the Kittiwalkers and figures like the one below, we are starting to gain a better understanding of the designs and locations that are most suitable for the next generation of kittiwake hotels.

how many nests were on the kittiwake hotels in Tromsø in 2024.

Figure by Dr. Macfarlane.


The last figure below tells an interesting story too. It shows the change in occupancy rates of the kittiwake hotels between 2023 and 2024.


Take hotel 1, which has space for 39 potential nests. In 2023 and 2024, less than one third of these potential 39 nests were used by kittiwakes.

Hotel 2 is the exact copy of hotel 1, but almost half of the 39 potential nests were used in 2023. However, in 2024, the occupancy rate dropped to one third. This suggests that design alone is not everything for kittiwakes. Hotel 1 was put very close to a building in 2023, at an angle that didn't allow kittiwakes to fly to and away from the nests, making it unattractive. Like hotel 1, hotel 2 was also close to the building, but at a different angle and this was enough to make it more attractive to kittiwakes.


Hotels 1 and 2 were moved to a new site between in 2024, near a cluster of trees. Unfortunately, this change did not appeal to the kittiwakes, and many pairs chose not to return to their previous nests—a remarkable outcome, given how strongly kittiwakes are attached to their previous nest! The proximity to trees proved unsuitable for kittiwakes, but hotels 1 and 2 also began deteriorating in 2024 as their wooden structures struggled to withstand the harsh Arctic weather. Maybe some of the kittiwakes from hotel 2 moved to hotel 3 in 2024. Studying the location of the ringed birds would help confirm this hypothesis. Hotel 4 has only point because it didn't exist in 2023 yet.

Number of nests on kittiwakes hotels in Tromsø in 2023 and 2024

Figure by Dr. Macfarlane.


What's next for the Kittiwalkers?


Citizen science is just one aspect of the Kittiwalkers' commitment to protect kittiwakes in Tromsø and to promote coexistence. At the last meetup (25 Nov.), 14 volunteers gathered in Fint kafé (if you haven't been yet, we strongly recommend the place) to celebrate the group's achievements and strategize for the next season. But that’s a story for another post. Stay tuned, we're just getting started!


The Kittiwalkers were meeting at FINT kafé in Tromsø to celebrate their achievements and strategize for the next season.ual meetup.

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