Warmer Arctic temperatures are dramatically affecting the roughly 240 bird species found north of the latitudinal treeline, helping most but hurting others.
Birding tours are becoming more popular in areas considered too inhospitable only a few decades ago.
By Rex Graham
Complex, unpredictable ecological changes that are still playing out are benefiting many bird species as ice recedes north toward the pole. Sea lanes are more passable for birding cruise vessels. Birders can explore thousands of islands rarely if ever visited by humans.
While many Arctic shorebirds appear to be decreasing, Snow Geese populations are booming due to the earlier appearance of vegetation and insects and a longer growing season for goslings.
However huge numbers of high Arctic ponds, which have been breeding habitat for waterfowl and sources of drinking water for mammals for millennia, have dried up or become ephemeral. “The ecological ramifications of these changes are likely severe, and will cascade throughout the Arctic ecosystem,” Canadian researchers wrote in Proceedings of the National Academy of Sciences (U.S.).
The signature Arctic migratory bird, the Arctic Tern, changes its breeding locations in the Arctic rapidly in response to changing conditions. It breeds from the high Arctic to temperate regions, such as the British Isles. A warming climate is expected to send the terns farther north to breed.
A study by British researchers published in Diversity said the best predictive models indicate that the Arctic Tern, Black-legged Kittiwake and several auk species will “decrease considerably” as the British Isles warm.
There are many uncertainties and confounding variables that models will certainly miss. For example, the researchers said the Lesser Sand eel or Sand Lance, an important prey species of terns and other seabirds along all the coasts of the British Isles, is expected to decline. However, the sand eel’s decline “may result in increased abundance of others, such as the European Anchovy.”
European Pied Flycatcher
The eggs of European Pied Flycatchers that breed in the far north of Finland are significantly bigger than in the past. In general, bigger eggs mean healthier chicks.
“Global warming may have favourable effects on the reproduction of birds,” Finnish flycatcher researchers wrote in the journal Ecography. “This in turn may help them rapidly conquer new areas when these become available and compensate for rising mortality rates to be expected elsewhere where warming means desiccation.”
The 1°C rise in mean surface-air temperatures from 1963 to 2004 in the treeless western part of the Alaskan Peninsula has resulted in 10 fewer days below freezing and 14 fewer days when ice prevents birds from accessing food resources below the water’s surface.
The result? More Brent Geese are staying behind in the Alaskan Peninsula rather than migrating south in search of eel grass, a nutritious marine plant that grows in shallow saltwater lagoons and bays.
Aerial surveys of Brent Geese (also called Brant) in winter in the bays of the Alaskan Peninsula’s Izembek Lagoon rose from an average of 110 birds before 1976 to 1,331 after 1976. “The milder winter conditions and reductions in ice cover have improved the accessibility of eelgrass and reduced thermoregulatory demands for wintering Brant in Alaska,” U.S. and Canadian researchers wrote in a 2009 study the journal Arctic.
The Thick-billed Murre is the Adélie Penguin of the Arctic. Both Adélies and the murres require coastal oceans with ice and open water to provide access to fish found immediately under the ice. In the murre’s case, scattered patches of open water help it reach Arctic Cod, their preferred prey found under floating sea ice.
The favorable ice conditions on the high Arctic northern limits of the murre’s breeding colonies are helping them flourish there, while the seabirds are declining on the southern limit of its range near Hudson Bay where ice conditions are less favorable. “This type of population shift in relation to global warming has been widely predicted,” said researchers with the Canadian Wildlife Service in the Journal of Animal Ecology.
Because of warming conditions, the Arctic flock of Snow Geese is expected to double every 3–4 years across its breeding habitat in northernmost Alaska, Canada, Greenland and Russia’s Wrangle Island.
“Warming temperatures have created advantageous conditions for successful breeding and molting by geese on the Arctic Coastal Plain,” states a U.S. Geological Survey (USGS) report.
Snow Geese eggs hatch 4-7 days sooner than they did 30 years ago, which gives the goslings earlier access to food than later-hatching goose species. For example, although more Brent Geese are spending the winter farther north in places like the Alaskan Peninsula, they and White-fronted Geese nest later than Snow Geese and not prosper in places where they nest near Snow Geese.
Nitrogen, an indicator of nutritional value, peaks in plants eaten by geese during the earliest part of the nesting season. The easiest-to-digest plants are most available during this time, according to a 2015 study in Avian Conservation Ecology.
Farther south in the low Arctic where temperatures also are climbing, some small ground-nesting birds are increasing while others are not. For example, a lowland area of Canada’s Ellesmere Island, which is west of Greenland, is home to Snow Buntings, Lapland Longspurs, Baird’s Sandpiper and other birds.
The density of the buntings, longspurs and sandpipers rise and fall more or less in unison in 16-year cycles.
Between 1980 and 2008, a long-term monitoring study published in 2003 the journal Arctic found a 3-fold increase in Lapland Longspurs, but no change in the density of other birds that nest in the area. The longspur increase was attributed to more luxuriant growth of grasses and sedges on Ellesmere Island.
However, hundreds of miles south in Cape Churchill, Manitoba, Canada, where longspurs nest alongside Snow Geese, the grass tends to be more closely clipped and longspur numbers there have decreased since the 1930s, according to a 2005 report in The Canadian Field-Naturalist.
“Multi-decadal, standardized monitoring studies establish baseline breeding-bird densities and provide insight into how Arctic bird populations are responding to climate change, as well as to other factors,” said the authors of the 2003 study in Arctic.
Milder winters have led to another unforeseen effect: more freeze-thaw events result in ice crusts that cause “dramatic population crashes” of reindeer and musk ox. The herbivores starve when their forage is covered by the crusts.
Arctic sea ice has decreased 3 percent per decade since 1970, which is disastrous for Polar Bears, which hunt seals on the winter ice.
The Arctic Fox is the only endemic terrestrial predatory mammal of the Arctic. In years when there are few lemmings and voles, the foxes eat many more eggs and chicks of geese and shorebirds. The Arctic Fox is being pushed north by a steady northward invasion of the larger Red Fox. Eventually, high Arctic islands may be the last refuge for the fox with white winter fur, according to researchers with the Norwegian Polar Institute and the University of Tromsø in Norway.