Mapping the Extraordinary Journeys of Arctic Terns

Arctic Tern / Photo by Ólafur Larsen

I have posted before about some of the incredible migration flights undertaken by birds, such as the nonstop flights of Bar-tailed Godwits across the Pacific or the circumoceanic wanderings of Sooty Shearwaters. Red Knots travel each year from Patagonia to the Arctic and back, as do some other shorebird species. Another bird species that undertakes impressive migration flights is the Arctic Tern (Sterna paradisaea). Every year, Arctic Terns make a 43,000-mile round trip between their wintering grounds in Antarctica and their breeding grounds in the Arctic.

The terns' routes were finally mapped through a banding study that outfitted each of the banded terns with tiny geolocators to track the birds' geographical locations along the way.

The first surprise is that the terns do not make straight for the Antarctic when they leave the Arctic, but make a lengthy stop-over in the middle of the North Atlantic, about 1,000km (620 miles) north of the Azores.

Here, they feed on zooplankton and fish to fuel themselves for the long journey ahead.

Terns take one of two routes on the way south:

The birds then head south along the coast of western Europe and western Africa before making a choice, either to continue hugging Africa or sweep across the Atlantic from the Cape Verde Islands to continue the journey along the Brazilian coast.

About half the birds that were tracked decided to take the South American path. It is not clear why, but the researchers believe wind might make either route seem favourable to the terns.

After spending their northern winter months in Antarctic waters, the terns then fly back towards the Arctic.

But rather than retracing their southward flight paths, the birds follow a gigantic "S" pattern up the middle of the Atlantic Ocean.

Interpolated geolocation tracks of 11 Arctic terns tracked from breeding colonies in Greenland (n = 10 birds) and Iceland (n = 1 bird). Green = autumn (postbreeding) migration (August–November), red = winter range (December–March), and yellow = spring (return) migration (April–May). Dotted lines link locations during the equinoxes. Credit: Greenland Institute of Natural Resources.

The spring route carries the terns northward along the west coast of Africa and then along the east coast of North America. (See the maps included in the BBC article.) This may mean traveling a longer distance than a more direct route would be, but the article's authors explain the different migration routes in fall and spring based on prevailing winds. It may be more energy efficient for the birds to move clockwise in the North Atlantic a counter-clockwise in the South Atlantic since they can benefit from a tailwind both ways. It is worth noting that ocean currents follow a similar pattern and could potentially influence the ease of finding food along the way.

Whatever the reason for their routes, these terns give us an additional reason to marvel at the natural world and its avian inhabitants.

Update: I added the map of the terns' routes from the project website, which has additional images and information: http://www.arctictern.info/

International Year of Biodiversity

A critically-endangered bird species / USFWS Photo

The U.N. has declared 2010 an International Year of Biodiversity in the hope that greater awareness might stem the ongoing extinction crisis. Many conservationists consider the current crisis to be the earth's sixth mass extinction. The U.N.'s current effort follows in the wake of unsuccessful efforts to reduce biodiversity loss.

The UN Convention on Biological Diversity (CBD) was agreed at the Rio Earth Summit of 1992, alongside the climate change convention.

But it acquired its key global pledge during the Johannesburg summit of 2002, when governments agreed to achieve a "significant reduction" in the rate of biological diversity by 2010.

Conservation organisations acknowledge that despite some regional successes, the target is not going to be met; some analyses suggest that nature loss is accelerating rather than decelerating.

Stemming the tide of extinctions is important in its own right, but it takes on added significance since properly functioning ecosystems provide services that are expensive to replicate.

A large on-going UN-sponsored study into the economics of biodiversity suggests that deforestation alone costs the global economy $2-5 trillion each year.

In his speech at Monday's event, United Nations Environment Programme (UNEP) executive director Achim Steiner is due to highlight problems caused by invasive species, and the potential for ecosystems such as forests and wetlands to absorb and store carbon from the air.

The UN hopes some kind of legally-binding treaty to curb biodiversity loss can be agreed at the CBD summit, held in Japan in October.

One element is due to be a long-awaited protocol under which the genetic resources of financially-poor but biodiversity-rich nations can be exploited in a way that brings benefits to all.

However, given the lack of appetite for legally-binding environmental agreements that key countries displayed at last month's climate summit in Copenhagen, it is unclear just what kind of deal might materialise on biodiversity.

After the dispiriting turn of events at Copenhagen, I do not have high hopes for what the coming biodiversity summit will produce. However, any improvement over the current state of affairs would be welcome, particularly if negotiators can find a fair way to reduce tropical deforestation.

To see which species are in danger of extinction, see the IUCN Red List, which is the most comprehensive catalogue of threatened species. Among the world's birds, 192 are considered Critically Endangered, an IUCN category indicating that a species has undergone rapid loss in its population and has a high likelihood of becoming extinct without immediate action. TIME also has a list of highly endangered creatures, but that list is more skewed towards large, charismatic mammals. The Endangered Species Print Project has an artistic way of looking at biodiversity loss.

A Wilderness Trail in the Great Swamp

Yesterday I was in a portion of the Great Swamp that I had not walked through before. I have probably been to Lord Stirling Park more than any other part of the swamp. Judging from reports  on JerseyBirds, most birders seem to frequent the areas around Pleasant Plains Road and the Long Hill Road boardwalk trails. More than half of the National Wildlife Refuge lies east of Long Hill Road and is designated as a "wilderness area." I am not sure that a refuge in the center of New Jersey is a good example of "an area where the earth and its community of life are untrammeled by man," as described by the Wilderness Act; it certainly does not feel that way when the trailhead is surrounded by a housing development. Nonetheless, this area of the Great Swamp was the first refuge to be designated as a wilderness in 1968.

Wilderness as it may be, this trail was pretty quiet yesterday. The most activity I saw was from a single flock of sparrows. Most of these were Dark-eyed Juncos, with a healthy mix of White-throated Sparrows, Song Sparrows, and (best of all) a few American Tree Sparrows. Nearby was a small flock of Eastern Bluebirds. At a different point, there were a few Swamp Sparrows, and near the end of the walk a large flock of American Robins flew overhead. Other than that, there were few birds to be seen.

I suspect that this trail may be more productive during the breeding season, when some swamp specialties would be in the area. It may also be more productive when the water is not frozen. The trail passes through several areas that appear to be open or wooded swamp, which ought to host Wood Ducks and other waterfowl during the appropriate seasons. Despite the lack of birds, this less-traveled trail offered some solitude and beatiful scenery.

Gray Squirrels Not Causing Bird Declines

The Eastern Gray Squirrel (Sciurus carolinensis) is a relatively recent addition to the fauna of the British Isles. The species's rapid spread has led to fears that it will displace native fauna that are already under pressure. According to one recent study, recent declines in the U.K.'s woodland birds are not being caused by the introduced gray squirrels.

BTO ecologists Dr Stuart Newson, Dr David Leech and Dr Chris Hewson and NE's Dr Humphrey Crick and Mr Phil Grice examined 38 bird species associated with woodland, including common starlings, wood pigeons, wrens, woodpeckers, thrushes, warblers, tits and finches....

Of the 38 bird species, a statistically significant relationship between grey squirrel and bird population sizes was found for 12 species.

Of those, squirrels appeared to have a positive impact on seven bird species, a correlation probably caused by both mammal and bird species benefiting from similar changes to their habitat.

Grey squirrels had a negative impact on just five: the common blackbird, Eurasian collared dove, green woodpecker, long-tailed tit and Eurasian jay.

"Of these species, the most convincing evidence is for blackbird and collared dove," says Dr Newson.

For these two species, the researchers found a weak but significant relationship between the abundance of grey squirrels and a failure of the birds' nests.

However, while grey squirrels may be predating on these two species, the overall number of blackbirds and collared doves has gone up nationally, and even locally where grey squirrels are common.

Of course, the study does not rule out negative effects on species not included in the study, such as hawfinches. It also does not negate the very real problems that gray squirrels are causing for Britain's native red squirrels (Sciurus vulgaris).

Loose Feathers #220

Greater Sage-Grouse / Photo by Thomas Barnes (USFWS)

Bird and birding news

• The wind and fossil fuel energy industries expect more restrictions if the Greater Sage-Grouse is listed under the Endangered Species Act. A decision on the species is due by the end of February.
• In related news, BLM issued new guidelines for energy development within the Greater Sage-Grouse's range.
• Medium ground finches on the Galapagos Islands have developed defenses against two invasive parasites, a pox virus and a nest fly. The Galapagos is unusual in that none of its native birds has gone extinct since humans arrived.
  
• Audubon has a profile of Rosalie Edge, the found of the Hawk Mountain Sanctuary based on a forthcoming book. The author writes that Edge has languished in obscurity until now, but there was actually a profile of her in Weidensaul's Of a Feather.
• Speaking of Hawk Mountain, this fall its hawk watch recorded 15,559 raptors. The count broke records with 68 Peregrine Falcons and 212 Bald Eagles.
  
• The New York State Ornithological Association put past editions of The Kingbird, its quarterly journal, online in a searchable archive.
  
• Relocation of burrowing owls for a housing development in California is going ahead over the objections of local conservationists.
• Tri-State Bird Rescue and Research (in Newark, DE) is looking for donations to help treat a group of Brown Pelicans that were found suffering from frostbite in southern Maryland.
  
• The Post-Crescent has an account of watching Short-eared Owls at dusk.
• A Northern Wheatear showed up in Texas this month.
  
• Birders on Christmas Bird Counts made greater use of real-time communication technology this year.
• Northern Ireland suspended its waterfowl hunting season due to a severe bout of cold weather.
  

Birds in the blogosphere

• Earbirding: Pacific Wren's a Done Deal
• The Hawk Owl's Nest: Would You Count It? A CBC Conundrum
• Tails of Birding: Champions of the Christmas Bird Count
• Outside My Window: Anatomy: Wing Coverts
• Binoculars Blog: Birding Snobs
  
• Hawkwatch at the Franklin Institute: They're back!
  
• Bird Canada: Bird (?) Watching
  

Environment and biodiversity

• The EPA announced new smog rules that limit ground level ozone to 60-70 parts per billion. During the Bush administration, the standard was set at 75 parts per billion. According to an EPA estimate, the lower standard could save several thousand lives per year.
• Here is a review of Obama's environmental policy accomplishments and shortcomings in his first year in office.
• A recent study shows that beach grooming reduces the availability of natural vegetated habitat.
• Fossil tracks show that tetrapods invaded land 18 million years earlier than previously known.
• A new study attempts a comprehensive evaluation of the effects of mountaintop removal mining and finds that it is as bad as one would imagine. The report came in the same week that the EPA dropped its objections to a mine of this type in West Virginia.
  
• Secretary Salazar announced that the administration would abandon the "drill anywhere" policy followed by the previous administration. What the new policy will be is unclear.
  

Carnivals and newsletters

• I and the Bird #116
  
• Berry Go Round #23
• Carnival of the Blue #32
• Circus of the Spineless #46
• Festival of the Trees #43
• Carnival of Evolution #19