Local research investigates effects of global climate change on red knots

For the last 15 years, rocky alpine ridges along the Teller Road have been the site of the world’s longest-running study of red knots on their breeding grounds.

In 2009, when U.S. Fish and Wildlife Service biologist Jim Johnson happened upon the red knot breeding area west of Nome, almost nothing was known about the red knot subspecies, roselaari, that breeds in this region. Since 2010, each summer except for 2020, Johnson and his colleagues have been documenting the breeding biology of this previously unstudied red knot subspecies (see Birder’s Notebook in the September 21, 2023 edition of The Nome Nugget).

In 2016, the scope of local red knot research expanded when Johnson began an exciting collaboration with bird ecologist Jan van Gils of the Royal Netherlands Institute for Sea Research, or NIOZ, and the University of Groningen in the Netherlands. Van Gils specializes in the effects of climate change on shorebirds.

Van Gils is known for his previous work on the impact of climate change on the rapidly declining red knot subspecies, canutus, that breeds in Siberia and winters in West Africa.

Polish ornithologists have been catching juveniles of the canutus subspecies during their southward migration to Africa since 1983. Van Gils and his colleagues found that these knots had become about 20 percent smaller in size since the Polish captures began. On top of that, they were able to link the knots smaller body size and shorter bill and leg lengths to a warming climate on their Siberian breeding grounds.

Since the 1980s, spring snow melt in Siberia has shifted an average of one month earlier. As a result, peak availability of insects—which fuels chick growth—often occurs earlier in the season, while the timing of chick hatch has remained basically unchanged. When insects are needed to feed growing chicks, their peak availability is often past. This misalignment means that chicks may not have the food they need to grow and survive.

Crane flies were found to be the most important food for young Siberian knots, and they are most abundant about 28 days after snow melt. By analyzing the proportion of nitrogen and carbon isotopes in knot feather and blood samples, van Gils could determine what the young knots had been eating. He found the proportion of crane flies in the diet was 50 percent higher for large juvenile knots than for small juvenile knots.

When food is scarce on the Siberian breeding grounds, van Gils discovered, the young birds pay the price on their African wintering grounds. There, the knots with shorter bills can’t probe deep enough to reach their primary, energy-rich food source––bivalves (small mollusks), that are buried in intertidal mud. Forced to switch to a less-nutritious, vegetarian diet, the short-billed knots eat rhizomes (underground stems) of seagrass.

The researchers found that young knots with normal bill lengths have an 80 percent chance of surviving to adulthood, while only 20 percent of those with short bills survive.

In 2022, van Gils was preparing to return to the Siberian breeding grounds to continue his research when the war in Ukraine broke out, curtailing his work in Russia for the foreseeable future.

Wasting no time, van Gils contacted Johnson, who was enthusiastic about collaborating and supporting a continuation of van Gils’s work on the roselaari breeding grounds near Nome.

During the past three summers, van Gils and his team of graduate students from the Netherlands have continued the long-term study of chick growth and survival as it relates to insect abundance and environmental conditions.

The biologists locate nests, then repeatedly find, capture and take measurements of red knot chicks in order to document their growth until fledging. This is not as easy as it might sound. The nests and birds are well camouflaged. Finding them requires many hours and miles of walking over rugged terrain each day or night. The chicks become more mobile and elusive by the day.

Watching van Gils and his fit, determined crew in action, one sees that they are up to the task. They exude the passion, curiosity, innovation and hunger for knowledge that drive dedicated scientists in all fields.

New technologies have made it much easier for the researchers to find the few red knots and nests scattered, almost invisibly, across a vast area of rocky tundra.

In 2022, the team experimented with using an infrared camera on a drone and a pair of infrared binoculars. The heat-sensing binoculars were a major breakthrough, and in 2024 the team used three pairs. This often requires the scientists to work during cooler nighttime hours; the binoculars work best when there is a greater difference in temperature between the ground and the birds.

The team monitors environmental conditions with portable weather stations placed in three locations within the study area. They track insect abundance during the breeding season with small pitfall traps scattered throughout the nesting area. The traps provide a measure of insect availability and show the timing of peak insect abundance.

Since 2010, Johnson’s research has documented annual variations in red knot productivity that occur under differing environmental conditions. Van Gils’  team has been fortunate to experience contrasting conditions over the last three years for comparison.

In 2022, snow melt occurred very early. Not many knots nested that year, and only five nests were found. Insects hatched early, too, and were no longer abundant when the chicks hatched. Only 25 percent of the chicks survived to fledge. It was the lowest survival rate since Johnson’s study began in 2010.

In 2023 and 2024, snow melt was late—and chick survival was much better.

In 2023, 11 nests were found, and it was one of the best growth years for chicks since monitoring began in 2010. Insects were abundant and hatched relatively late, so they were available for late-hatching knot chicks. Chick survival was high.

In 2024, a record 16 nests were found, thanks largely to the three pairs of infrared binoculars. Chick survival was high for all but the latest broods, which faced heavy rains in July when the chicks were still very young.

In addition to continuing the long-term data collection begun by Johnson, van Gils has begun investigating what drives fluctuations in productivity.

In the last two years, van Gils designed and conducted experiments to study the relationship between the growth of red knot chicks and the abundance of insects in different environmental conditions.

In 2023, graduate student Anne Vorenkamp, from the University of Groningen, conducted experimental feeding trials. Her study was designed to examine the rate of chick growth in relation to food supply to determine the minimum food requirements for growth and survival.

Vorenkamp wondered: In order to grow, do younger, smaller chicks need a higher density of available food than do older, larger chicks, or vice versa? To find out, the team collected a clutch of eggs from a red knot nest in the study area. After the young knots hatched, Vorenkamp caught insects and ran experiments with the chicks as they grew while in captivity. 

The preliminary analysis by Vorenkamp shows that larger chicks can detect prey from further away, can walk faster to capture it, and can handle it more quickly than do smaller chicks. This enables them to increase their food intake with age. When data analysis is complete, the results should show the amount and density of food that chicks of different ages need to grow.

In 2024, graduate student Roos Winters collected fecal samples from chicks in the field. She is conducting DNA analysis in the lab to determine what the chicks were eating, and the proportion of different insects in their diet.

Van Gils’ team also experimented with a novel technique using accelerometers—small electronic devices attached to the leg or back of a chick in order to measure the chick’s activity. Lorenzo Micolucci, another graduate student of van Gils, is just beginning to analyze these results.

Eventually they hope to correlate activity with insect abundance to determine whether chicks move more (work harder) when insects are less available. Insect scarcity for chicks could be caused by poor weather, bad timing of hatch relative to insect abundance—or both.

It would be very interesting to know if our roselaari red knots are, like the red knots that breed in Siberia, getting smaller. However, data collection on the subspecies only began when Johnson began his study in 2010. There is no long-term data for comparison with the roselaari on their wintering grounds.

In the early years of Johnson’s research, very little was known about the red knots that breed in this region––not even where these birds wintered. Researchers in Nome and beyond have learned a lot in the last decade. 

In 2009, the roselaari population size was estimated at 21,000 knots. Attempts are being made to repeat that study to determine the roselaari population trend. Most red knot subspecies are declining, but the population trend for roselaari is unknown.

Recent genetic analysis found that the roselaari breeding in northwest Alaska are genetically distinct from those breeding on Wrangel Island in Russia. Tagging studies led by Johnson have revealed that most of both populations winter along the Pacific Coast from southern California to northwestern Mexico.

The fossil record shows that prior to extinction, species tend to become smaller. Thus, when studying the shrinking canutus red knots in Siberia and West Africa, it seemed to van Gils that he could be documenting a species edging toward extinction.

But van Gils is an optimist. He says that birds can be resilient and adaptable if given a chance.

Van Gils cited a subspecies of bar-tailed godwits that breeds in Russia and winters in Mauritania. They, too, were impacted by climate change, which caused a mismatch of chick hatch and peak insect abundance.

Over time, the godwits spent less time at their migratory stopover in Europe’s Wadden Sea, in years when food there was abundant. The Wadden Sea is a protected UNESCO World Heritage Site used by thousands of migratory birds.

In those years of abundant food, the godwits now arrive on their breeding grounds earlier and chick hatch coincides with peak insect abundance. By preserving critical habitats to allow migrants to continue to rest and refuel at their traditional productive stopover sites, we give knots and other migratory species a chance to adapt, too.

According to Johnson, long-term studies provide valuable insights about how resilient—or not—species are to the changing climate. Based on van Gils’ research on canutus, red knots are sensitive indicators of climate change.

Climate change impacts are difficult or impossible to control, and only time will tell how roselaari knots will fare in a warming climate. In the meantime, Johnson adds, it’s important to focus on factors that we can control, such as protecting critical habitats.

“We can learn from the birds as canaries in the coal mine, because they tell us a global story,” says van Gils. “They tell us that the world has troubles, and we should listen to them.”

The song of a red knot during a flight display on the Nome area breeding grounds can be found here: https://macaulaylibrary.org/asset/33229401

The chicks from the feeding trial are now adults and part of an educational shorebird exhibit at the Monterey Bay Aquarium in California. They can be seen by webcam in the aviary along with many other shorebird species at this link:

https://www.montereybayaquarium.org/animals/live-cams/aviary-cam