‘Knots are being pushed to their limits’

Dr Jan van Gils, senior scientist at the Department of Coastal Systems Research was awarded the prestigious VICI grant in 2019, with which he upscaled his research on Arctic-breeding birds. ‘We discovered that knots respond to Arctic warming by moving uphill, in their quest for well-timed food for their chicks.’

For Dr Jan van Gils, 2019 could not have started better: in February he was awarded the prestigious VICI-award by the Dutch Research Council NWO. ‘I am extremely happy with this’, Van Gils says. ‘First of all, there aren’t that many VICI-awards in ecology. Moreover, VICI is a personal scholarship, almost without any limitations. Therefore, it enables me to do curiosity-driven research into the theme that intrigues me most: how our migrant shorebirds cope in our rapidly changing world. Notably, how rapid warming of their Arctic breeding grounds has cascading effects on their lives, even when they are wintering in coastal systems further south. One major problem for them is the earlier onset of the Arctic summer, making it difficult to arrive in time to take full benefit of the abundant insects that crawl out of the thawing soil.’

Already in 2018, Van Gils and colleagues went on a first expedition to the most northerly edge of the Russian mainland, Taimyr Peninsula. ‘Our Russian collaborator, Mikhail Soloviev, who had visited the region in the early 1990s, made a suggestion where to pitch the camp, based on high densities of breeding knots back then. However, upon arrival in 2018, it became clear that hardly any birds were breeding around the camp anymore! It appeared they had moved uphill, more than two hours walking away from our camp!’ In 2019, Van Gils and colleagues visited Taimyr again. ‘This year, we were able to show why climate change had driven the birds uphill. Since they cannot go any further north on the peninsula, the only way to find a cooler climate is by moving higher. With every rise of 10 meters uphill, the insects appeared to emerge from the soil a day later. Therefore, a shift of 150 meters up, gives the birds two weeks extra time to raise their chicks and take benefit of the abundance in food.’

Knots that arrive in Siberia before the snow melts can give their chicks a head-start in life

‘Fundamental research may provide essential clues for conservation.’

The 2019 camp still surrounded by snow in early June

Chicks and parents are caught, weighed and colour-ringed

Mapping migration

A large proportion of his VICI-award will be invested in high-tech, miniature satellite transmitters, that can be glued onto the feathers of knots. Van Gils: ‘During our Taimyr-expeditions, we already carried out some successful pilots with these transmitters. Before the birds shed their feathers on their wintering grounds and therefore lost their transmitters, we were able to track them all the way to West-Africa, where they overwinter in the Mauritanian Banc d’Arguin. We were able to plot their complete autumn migration on the map! We were planning to tag new birds in Mauritania this spring, but the COVID-19 pandemic prevented us from doing so. We hope for better opportunities to map their spring migration in the years to come.’

Looking back into successful diets

There is more high tech in the knot research of Van Gils and his team. ‘Together with the NIOZ-Microbiology and Biogeochemistry lab, we are analyzing the isotopes of nitrogen and carbon in the feathers of knots that have just arrived in Siberia. This shows what the birds were eating while growing these feathers in Mauritania. More specifically, these atomic fingerprints reveal whether they preyed on their favourite bivalves, or whether they “filled up their tanks” with seagrass roots, before leaving for Siberia. It appears that the birds that arrive first in Siberia, have the best odds for successfully raising chicks.

I hope to find out whether the key to this success lies in their African diet. That way, we may be able to find some opportunities for mitigating the climate-change effects. Even if we are able to lower our carbon emissions, the knots will suffer from temperature rise in the Arctic for quite a while. So I hope that our fundamental science provides clues for conservation.’

Will the chicks hatch in time as the nutritious insects crawl out of the thawing soil?

Apart from collecting descriptive field observations in Taimyr and Mauritania, Van Gils also takes the experimental approach. ‘In our Siberian base camp, we carried out a pilot to raise chicks, while carefully measuring their energy budget using “heavy water” containing – harmless – deuterium atoms. Some say that rising temperatures may benefit birds in the Arctic because they need less energy to keep warm. We don’t see this in the field at all, but the golden standard in science is the experiment. In future expeditions, we aim to perfect these experiments.’

The Dutch-Russian expedition crew at Taimyr Peninsula, Siberia