A few years ago, things didn’t look so good for the ptarmigan in Finnmark, northernmost Norway. But 2023 was a good year for this northern bird. Why do its numbers fluctuate? Professor Rolf Anker Ims at UiT The Arctic University of Norway explains what ptarmigan populations need in order to thrive.
By: Ellen Kathrine Bludd // UiT The Arctic University of Norway
The two species, rock ptarmigan, and willow ptarmigan, are in the middle of the food chain.
“Ptarmigan feed on vegetation, so they need a certain amount of food plants present, and an entire community of predators eat ptarmigan at different life stages. Both eggs, chicks, and adults are eaten,” says Ims.
Desirable game
He explains that crows, ravens, foxes, and stoats rob nests. Chicks are good food for anyone who eats meat, while the gyrfalcon specialises on adults. Golden eagles also love ptarmigan.
“It’s desirable game for many animals, including humans,” he says.
But all predators also eat lemmings.
“When there is an abundance of lemmings or other small rodents, the ptarmigan gets a year off from this predatory pressure,” says Ims.
This leads to good production of eggs and great survival.
Hopeless camouflage
Weather and climate also affect the bird.
“In spring, when the chicks hatch, they are vulnerable to cold and wet weather. At that point they are almost ‘cold-blooded’ and need to be warmed by their mother. But they must go out in the open to eat.”
Rolf Anker Ims, UiT The Arctic University of Norway
Chicks eat insects the first week, then switch to plants for food. Therefore, the weather during egg hatch is crucial. In spring 2023 there were a lot of small rodents, and the weather was good when the chicks hatched. But with climate change, the climate will be wetter and wilder, so there may be tougher times ahead for the bird. Ptarmigan are well adapted to winter conditions, but in the future, we may have shorter winters. Late snow means trouble for the ptarmigan.
“Ptarmigan turn white in autumn as camouflage. But being a white bird against a dark background doesn’t work well as protection from predators. They become hopelessly visible,” says Ims.
Moulting, the process where old feathers are replaced by new ones and a bird’s plumage changes colour, is controlled by light, not by snow. Day length signals change. A late winter means there will be fewer ptarmigan the following spring because more of them will have been eaten.
In autumn 2022, the snow came early, which was good news for the population in 2023.
Historic ptarmigan populations
Ptarmigan populations have always fluctuated, but historically the numbers were higher.
“2023 was Finnmark’s best year for ptarmigan in almost 20 years, but historically, it’s nothing to brag about,” says Ims.
Populations of ptarmigan in all of Norway have declined.
“The distribution range is shrinking northwards and in altitude, as climate change affects the ecosystems,” Ims says.
Lemmings also face bad times.
“Lemmings have been hit hard by climate change and good years are far and few between. Mild winters, when it sometimes freezes over again, make it hard for small rodents to get under the snow to eat.”
Rolf Anker Ims, UiT The Arctic University of Norway
In the past, there was a lemming year approximately every four years. Now this peak is sometimes aborted because of a bad winter. This disruption in the lemming cycle affects the ptarmigan. Ims and colleagues in the COAT project have been studying this cycle for years, providing knowledge that can be used in ptarmigan management.
Predicting ptarmigan numbers
“Once we know what the weather and the rodent population are like in spring, we use a statistical model to predict how large the willow ptarmigan population will be in the autumn,” says Ims.
The Finnmark Estate (FeFo) which manages 96% of Finnmark County, including the ptarmigan population, uses this information to prepare hunting quotas. Additionally, they do a manual bird count before the start of the hunting season. For the third year in a row, the predictions of the researchers’ model have been on target, and in 2023 FeFo was able to set a higher quota than in previous years.
Ims believes this is a good example of what the project COAT can be used for.
“We have good data on what affects the ptarmigan. Hence, we can contribute to what we call ‘ecosystem-based management’. Models like these provide forecasts which in turn provide sound management,” says Ims.
The hunt for one year is also included in the ptarmigan model for the following year.
“Hunting has a much smaller effect than small rodents and climate change,” says the professor.
He adds that the Norwegian biodiversity act stipulates that harvesting should be allowed only when there is a surplus and that it should not harm other species in the ecosystem. He emphasises that making good management choices early on is better than correcting them when disasters occur. “The ptarmigan management that FeFo is now carrying out is sustainable. In years with a small ptarmigan population, they set the quotas low. Then they can increase the quotas in good years,” says Ims.