All posts by George Divoky

Married to the Arctic

Cooper Island, Alaska, July 12, 2009 — Many bird species are thought to be “Arctic birds” because they migrate to the Arctic every spring, utilize the region’s resources for breeding, and then depart for more southern wintering areas in late summer and early fall, spending the majority of the year well south of the Arctic Circle. These species have a “summer romance” with the Arctic, enjoying the benefits of constant daylight and the abundant food resources provided by the region’s insect and fish populations. A much smaller number of bird species are truly “married” to the Arctic, remaining after breeding is done to cope with months of darkness, cold and ubiquitous snow and ice, apparently aware that in any committed relationship all cannot be 24 hours of sunlight.

Cooper Island is home to two species that represent extremes of these relationships with the Arctic. The Arctic tern, which used to be the most abundant species on the island, spends the non-breeding season in the extreme Southern Hemisphere in waters adjacent to the Antarctic. Its annual migration to and from the Arctic takes them many thousands of miles from Cooper Island –— and the southern location of their wintering areas allows them to experience more daylight annually than any other species.

On the other hand, the black guillemot subspecies that breeds in the western Arctic, including Cooper Island, is one of the few truly Arctic seabirds, wintering in the Arctic Ocean and into the Bering Sea only as far south as the pack ice extends in mid winter. Some individuals breeding on Cooper Island may well winter as little as 25 miles from the island in the ice pack north and west of Point Barrow, where winds and currents keep some areas of water open throughout the winter and guillemots are regularly seen by hunters on the winter sea ice. While the migratory strategies of the two species could not be more different, for two to three months every summer they both breed on Cooper Island and are dependent on marine prey adjacent to the island during incubation and while feeding nestlings. That both Arctic terns and black guillemots have suffered major decreases in population size and breeding success in recent years is an indication of how prey availability and abundance are changing in the marine waters of arctic Alaska.

The Arctic tern population on Cooper Island used to be the largest on any of the barrier islands in northern Alaska, with 150 breeding birds in small sub-colonies spread over the two-mile long island. This year there are only 20 breeding birds, restricted to one small patch of driftwood. The black guillemot population numbered slightly over 400 breeding birds in the late 1980s, with an additional 200 non-breeders. This year there are only 270 breeding birds with less than 50 non-breeders.

Because all guillemot young and most guillemot adults are banded we know more about the causes of their decline. Immigration of birds that fledged from other colonies, probably primarily Russian islands, played a major role in maintaining the Cooper Island colony. In recent years there have been far fewer immigrants. This appears to indicate that those colonies are also experiencing low productivity. With no immigration at current levels of breeding success, neither the terns nor guillemots can persist on Cooper Island.

One species of seabird breeding on Cooper Island, the horned puffin, has experienced an increase in numbers with 6-8 breeding birds in recent years. This doesn’t seem like much until one considers that the species was rare in Arctic Alaska until the 1970s and first bred in the region in 1986 when a pair occupied a nest box on Cooper Island —kicking out the guillemots that previously owned it. That this sub-Arctic species, that has no dependence on sea ice, is now breeding this far north is another sign of how warming of both the ocean and atmosphere is affecting the Cooper Island avifauna.

All of these species are now incubating eggs and I am anticipating the start of hatching in about a week. It is then, when parent birds have to continuously find fish for chicks, that the guillemots and terns experience troubles if prey abundance is low.

Getting Ready for Life on the Edge

Seattle, Wash., June 10, 2009 — After over three decades of conducting summer fieldwork on seabirds in Arctic Alaska one would think that pre-field preparations would be a matter of habit and that that the level of anticipation and anxiety associated with heading off to a remote island would be minimal. But as I prepare to spend three months living at the edge of the continent and pack ice studying black guillemots on Cooper Island, I am reminded of the philosophical observation that no man can step in the same river twice. Anyone who has spent time in the Arctic during the last decade does not need to be a philosopher to see that “all is change”. The Arctic I first visited in the 1970s bears little resemblance to that of the early 21st century. My camp used to consist of one or two small tents, I could arrive in late June just after snowmelt, and in plenty of time to see the start of guillemot egg-laying, and while I always took a shotgun with me, it frequently remained untouched during my stay on the island.

This year the winter snow melted in Barrow in late May continues a long-term trend of earlier snowmelt caused by warming air temperatures in April and May. My two small tents have been replaced by an 8×12 cabin I brought out over the ice from Barrow in early 2003 after polar bears ripped up two of my tents and ran me out of my camp in 2002. Since 2002 bears have become an almost daily presence on the island in late July and August, and I now have to carry a loaded shotgun constantly whenever I am out of the cabin (and keep it close to me when I am in the cabin). This rapid increase in bear activity in recent years is due to their preferred habitat, the Arctic pack ice, undergoing unprecedented decreases in summer and forcing bears to the shores of the Arctic Ocean, where many now spend late summer and fall waiting for the ice to return.

My long-term study of black guillemots, a diving seabird closely associated with pack ice, has shown how a warming Arctic has had major effects on the breeding biology of an Arctic resident. Guillemots need the snow to melt before they have access to their ground-level nest boxes and also need to have their young leave the nest before snow begins to accumulate in late summer. Until the late 1960s the period the ground was snow-free in Arctic Alaska was frequently less than the 80 days of nest access the guillemots need to raise young successfully. Due to warming over the last four decades guillemots now regularly have over 100 days of cavity access. The earlier snowmelt and later accumulation allowed guillemots to prosper on Cooper in the late 20th century as the restrictions of snow cover were reduced. However the same warming that facilitated access to nest sites was increasing the melt of pack ice adjacent to Cooper Island (and throughout much of the Arctic Basin). Black guillemots in the Western Arctic are dependent to a great extent on prey associated with pack ice. They feed in the pack ice throughout the winter and most colonies are adjacent to the summer sea ice. The guillemots primary prey item is Arctic cod, a species that specializes on feeding under and near Arctic sea ice. During the 1970s and 1980s when ice was typically within 20 miles of Cooper Island in August parent birds had little trouble finding enough prey to feed their young. In the last decade early and rapid retreat of the ice from the near shore has meant that guillemot parents find far less cod and as a result try to raise their young on prey that is less abundant and of lesser quality. This has resulted in breeding failures in recent years with many chicks starving in the nest sites or leaving the nests at very low weights.

The changes caused by increasing temperatures in the Arctic have affected my pre-field activities since in April or May. I now need to determine if polar bears have broken into my cabin as they did in the winters of 2004 and 2005. Cleaning up and assessing the damage done by a large curious and/or hungry carnivore in an 8×12 foot box is not a minor chore and best done before the start of the field season. So in late April of this year I went over the ice from Barrow to Cooper Island with my friends Robert Suydam and Leslie Pierce to see if the wood on the cabin door was still in place and the cabin ready for another field season. We were relieved to find that all was well with the cabin and also that the depth of the snowdrifts around the cabin was sufficient to provide me with drinking water for the first part of the season.

I travel to Barrow and Cooper Island late this week and will be sending weekly updates about my observations and experiences during my stay on the island this summer. Since much of what happens on the island is dependent on the retreat of the sea ice I will also attempt to have updated satellite imagery showing ice conditions in the area of Point Barrow and Cooper Island. An early June ice image shows that while there is extensive shore fast ice north of Cooper Island, there is a rather larger area of open water north of that and that the pack ice is composed for relatively small ice floes for this time of year.

Looking forward to another summer in the Arctic and being able to share stories and images from the island.

Preparing for the 2009 Field Season

Seattle, Wash., June 1, 2009 — In 2008 fledging success of black guillemots was again low. Unlike past years, when chicks died as a result of prospecting horned puffins occupying nest sites and a lack of Arctic cod, in 2008 chicks had to deal with snow storms blocking nest entrances and stranded polar bears flipping over nests as they scavenged the beaches for food.

The 2009 field season promises to be another interesting one as the melt season begins with the Arctic Basin having a large percentage of of thin first-year ice, according to the National Snow and Ice Data Center. Should ice melt progress as it has in recent years the period when parents are feeding chicks (late July to early September) will see the pack ice retreat well away from the island. Black guillemots will then be unable to find Arctic cod, their preferred prey and most accessible under pack ice. Should the ice retreat rapidly and strand polar bears on the beach, the guillemots and puffins breeding on the island (and the researchers studying them) will have to deal with displaced bears wandering the island looking for food.

Although the small carbon-footprint of our field camp complicates communications from Cooper Island, we hope to be able to provide regular text and photo updates to this website during the June-September field season. Please check back to see what is happening with the birds, the ice, the bears and us as the summer progresses.