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 SocietyE 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 oil fields 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.”
Morten Rasch from the Arctic Environment Dept of Aarhus University in Denmark is the coordinator of one of the most ambitious ecological monitoring programs in the Arctic. The Greenland Environment Monitoring Program includes two 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 ecosystems of the Arctic. At that time, he told me during an interview, 10 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 realize the entire growing season in these areas is only three 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 three 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.”
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 did not previously come this far north.
This story is posted on Alaska Dispatch as part of Eye on the Arctic, a collaborative partnership between public and private circumpolar media organizations.