Migratory birds that breed in the Arctic are starting to nest earlier in spring because the snow melt is occurring earlier in the season.
This is confirmed by a new collaborative study,”Phenological advancement in arctic bird species: relative importance of snow melt and ecological factors” published in the current online edition of the journal Polar Biology. The scientists, including Wildlife Conservation Society (WCS) biologists, looked at the nests of four shorebird species and one songbird in Alaska, recording when the first eggs were laid in the nests. The work was undertaken across four sites ranging from the oilfields of Prudhoe bay to the remote National Petroleum Reserve of western Arctic Alaska.
The scientists looked at nesting plots at different intervals in the early spring. Other variables, like the abundance of nest predators (which is thought to affect the timing of breeding) and satellite measurements of “greenup” (the seasonal flush of the new growth of vegetation) in the tundra were also assessed as potential drivers, but were found to be less important than snow melt.
Lead author Joe Liebezeit from the Audubon Society of Portland says “it seems clear that the timing of the snow melt in Arctic Alaska is the most important mechanism driving the earlier and earlier breeding dates we observed in the Arctic. The rates of advancement in earlier breeding are higher in Arctic birds than in other temperate bird species, and this accords with the fact that the Arctic climate is changing at twice the rate.”
Over nine years, the birds advanced their nesting by an average of 4-7 days. The researcher says this fits with the general observation of 0.5 days per year observed in other studies of nest initiation in the Arctic, of which, they say, there are not very many. The rates of change are much higher than those of observed in studies of temperate birds south of the Arctic.
Co-author Steve Zack from WCS says “Migratory birds are nesting earlier in the changing Arctic, presumably to track the earlier springs and abundance of insect prey. Many of these birds winter in the tropics and might be compromising their complicated calendar of movements to accommodate this change. We’re concerned that there will be a threshold where they will no longer be able to track the emergence of these earlier springs which may impact breeding success or even population viability”.
WCS Beringia Program Coordinator Martin Robards says “Everything is a moving target in the Arctic because of the changing climate. Studies like these are valuable in helping us understand how wildlife is responding to the dramatic changes in the Arctic ecosystem. The Arctic is so dramatically shaped by ice, and it is impressive how these long-distance migrants are breeding in response to the changes in the timing of melting ice.”
In connection with Migratory Bird Day some time ago, I talked to Ferdinand Spina, head of Science at Italy’s National Institute for Wildlife Protection and Research ISPRA, in Bologna, Italy. He is also in charge of the Italian bird ringing centre, and Chair of the Scientific Council of the UN Convention on Migratory Species, CMS. In the interview, he stressed that climate change is becoming one of the greatest threats to birds that breed in the Arctic.
“Birds are a very important component of wildlife in the Arctic. There are different species breeding in the Arctic. The Arctic is subject to huge risks due to global warming. It is crucially important that we conserve such a unique ecosystem in the world. Birds have adapted to living in the Arctic over millions of years of evolution, and it’s a unique physiological and feeding adaptation. And it is our duty to conserve the Arctic as one of the few if not the only ecosystems which is still relatively intact in the world. This is a major duty we have from all possible perspectives, including an ethical and moral duty, ” he says. We talked about the seasonal mismatch, when birds arrive too early or too late to find the insects they expect to encounter and need to feed their young.
This reminds me of a visit to Zackenberg station in eastern Greenland in 2009. At that time, Lars Holst Hansen, the deputy station leader, told me the long-tailed skuas were not breeding because they rely on lemmings as prey. The lemmings were scarce because of changes in the snow cover.
Jeroen Reneerkens is another regular visitor to Zackenberg, as he tracks the migration of sanderlings between Africa and Greenland. A great project and an informative website!
Morten Rasch from the Arctic Environment Dept of Aarhus University in Denmark is the coordinator of one of the most ambitious ecological monitoring programmes in the Arctic. The Greenland Environment Monitoring Programme includes 2 stations, Zackenberg, which is in the High Arctic region and Nuuk, Greenland’s capital, in the “Lower” Arctic. Hansen and other members of Rasch’s teams monitor 3,500 different parameters in a cross-disciplinary project, combining biology, geology, glaciology, all aspects of research into the fragile eco-systems of the Arctic. At that time, he told me during an interview, ten years of monitoring had already come up with worrying results:
“We have experienced that temperature is increasing, we have experienced an increasing amount of extreme flooding events in the river, we have experienced that phenology of different species at the start-up of their growing season or the appearance of different insects for instance now comes at least 14 days earlier than when we started. And for some species, even one month earlier. And that’s a lot. You have to realise the entire growing season in these areas is only 3 months. When we start up at Zackenberg in late May, or the beginning of June, the ecosystem is completely covered in snow and more or less frozen, and when we leave, in normal years – or BEFORE climate change took over – then we left around 1st September and the ecosystem actually started to freeze up. So the entire biological ecosystem only has 3 months to reproduce and so on. And in relation to that, a movement in the start of the system between 14 days and one month – that’s a lot.”
Listen to my radio feature: Changing Arctic, Changing World
I can’t write about birds and climate change in the Arctic without finishing off with a mention of George Divoky, an ornithologist whose bird-monitoring has actually turned into climate-change monitoring on Cooper Island, off the coast of Barrow, Alaska. George looks after a colony of Black Guillemots and spends his summer on the island. In recent years, he has taken to putting up bear-proof nest boxes for the birds, because polar bears increasingly come to visit, as the melting of the sea ice has reduced their hunting options. He has also observed the presence of new types of birds which die not previously come this far north.