Category Archives: Black guillemot

Trying to stay optimistic in a seabird colony that is half full – when it is really half empty

The standard and far-too-simplistic “test” of whether someone is an optimist or a pessimist is to ask if they consider half a glass of water to be half full or half empty.  The major flaw in the test is that it implies a steady state situation.  If the glass is being filled with water, one has reason to be optimistic about half a glass. If it is being drained, there is reason for pessimism.  The increasing or decreasing trend of a resource needs to be considered in deciding whether to be optimistic or pessimistic about the currently observed conditions.

This summer the Black Guillemot colony on Cooper Island had 100 breeding pairs.  Guillemots do not breed in the thousands or tens of thousands, as do many seabirds, and a 100-pair colony is a rather large aggregation of these beautiful birds. Anyone familiar with breeding guillemots who happened to visit Cooper Island this summer would likely be impressed with the 200 individuals breeding here.

However, it would be hard for anyone familiar with the history of the Cooper colony to be optimistic about its future.  Starting in 1975, we modified wooden boxes, floorboards and other debris on the island to create 200 nest cavities by the early 1980s. Guillemots quickly occupied the nest sites and the breeding population increased from 18 pairs in 1975 to just over 200 pairs in 1989 (graph below) when all potential nest cavities in the Cooper colony were occupied by breeding pairs.  

pairs and sea ice

This year, 2016, there are still 200 nest cavities.  The guillemots now nest in polar bear-proof Nanuk plastic cases that replaced each of the more vulnerable wooden sites in 2011.  The birds took to the new cases immediately, parent birds and nestlings clearly feel more secure in them and loss of nestlings to polar bears is now near zero – but this year half of the available nest cases are empty and no guillemots are breeding there.

We are currently examining the specific reasons for the colony’s decline to half of what it was in 1989 in collaboration with avian demographers but it is appears to be due to the guillemot subspecies on Cooper Island being one the few ice-obligate seabirds in the Arctic.  In a rapidly warming world the Arctic is the region that is warming most rapidly with dramatic and clearly visible effect on the region’s snow and ice habitats.  The decline in the Cooper Island colony started in 1990, the same year that warming temperatures in the region allowed the island’s guillemots to begin laying eggs earlier (as discussed in a previous post [link to last post]) and the decreasing trend in annual summer sea ice extent began.  Decreased summer sea ice has reduced the availability of the guillemots’ preferred prey, arctic cod, resulting in lower breeding success on Cooper Island and likely other colonies and, in this century, has increased polar bear presence on the island – which until we provided nest cases greatly reduced breeding success.

Given the loss of Arctic sea ice, it is not surprising that the Black Guillemots have also declined.  When the Cooper Island colony was near 200 pairs in the late 1980s, the annual minimum extent of sea ice in September averaged over 7 million square kilometers. As the guillemot population was declining in the last decade to its current 100 pairs, September sea ice extent has dropped as low as 3.6 million square kilometers – nearly half what it was when the Cooper Island study began.  In short, both Arctic summer sea ice and the Cooper Island guillemot colony have been reduced by half in the last quarter century.  

The future trajectory of summer sea ice seems clear.  Continued carbon emissions will cause continued warming, which will cause continued ice loss. All climate models project continued decline and eventual disappearance of Arctic sea ice if carbon emissions are not greatly reduced (graph below).  The path of the Cooper Island guillemot population, however, is less certain.  Like all animal populations the birds currently breeding on Cooper Island may possess sufficient behavioral plasticity to adapt and evolve to accommodate new conditions, just as their ancestors may have possessed when they adapted to exploit ice-covered waters.  Some guillemots may be able to survive and even prosper in an Arctic without summer sea ice – which, unlike the animals that have come to depend on it (including not only the Cooper guillemots but arctic cod, walruses, seals, and polar bears), cannot adapt and somehow stay frozen at temperatures above freezing.  

Observations of Northern Hemisphere minimum September sea ice extent (yellow line), and time series of global climate model projections (5 year running mean) and uncertainty (shading) for scenarios RCP2.6 (blue) and RCP8.5 (red). Black (grey shading) is the modelled historical simulation using historical reconstructed forcings. The RCP8.5 emissions scenario depicts a future where current rates of emissions continue unabated throughout the century, and the RCP2.6 scenario depicts a future in which the aims of the Paris Agreement are fulfilled.

Figure was adapted from the IPCC Summary for Policy Makers, 2013, Figure SPM.7b (

My days on Cooper Island in August are consumed with weighing nestlings.  Regular contact with the young of any species is bound to make one feel optimistic – it is still a wonder to me how quickly chicks grow from little balls of fluffy black down into gawky “teenagers” preparing to fledge into the Arctic Ocean, unaccompanied by their parents.  But as I walk through the colony seeing only open ocean to the horizon – where in decades past I saw large expanses of sea ice – I have to wonder how many young will survive to breed, and what conditions they may encounter should they return to Cooper to nest at sites we have been monitoring during the recent decades of rapid warming and plan to monitor in the even warmer future.

Early August has brought the first pulse of polar bears to Cooper Island, stranded here as their sea ice habitat that provides them a platform to walk on and hunt seals from is rapidly disappearing to the north. The bears, some of whom sleep for days on the island after swimming an unknown distance from melting sea ice, remind me that an entire biological community is being impacted by this halving, and eventual disappearance, of summer sea ice.  However optimistic I may feel about Black Guillemots’ ability to adapt to ice loss, I am aware I am observing the loss of one of the world’s most unique ecosystems.

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The eggs at J-09

Earliest breeding season in 42 years

The record setting snowmelt in Barrow this spring has resulted in the earliest breeding season for the Black Guillemots on Cooper Island in the 42 years the colony has been studied.

Median date of egg laying (when 50 percent of the nests have eggs) was June 16th. Three days earlier than the previous record – set in 2015. Early breeding is important this summer as birds may be able to have their young fledge before the major loss of sea ice predicted for August.

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Guillemot Early Breeding Season and New Cooper Island Publications



George Divoky and North Slope Borough Search & Rescue pilot Brian Burke preparing the helicopter for the flight out to Cooper Island June 11.

Fieldwork at the Black Guillemot colony on Cooper Island began in early June, where I began the fifth decade of research on a remote island in a rapidly changing Arctic. Just how rapidly that change is occurring was obvious on the first day in the field, June 11, 2015, when I discovered that egg laying had already begun, with the first egg laid some two weeks earlier than the average date of the first egg over the last four decades. The early laying was a direct result of an extremely early snowmelt in Arctic Alaska that provided Black Guillemots access to nest cavities in late May. A future post will have more details on what the unprecedented timing of this breeding season means for the Cooper Island guillemot colony and in the context of the forty years of observations of breeding chronology that precede it.

I discovered that egg laying had already begun, with the first egg laid some two weeks earlier than the average date of the first egg over the last four decades.

While long-term changes in snowmelt are affecting the start of the guillemots’ breeding season, long-term changes in summer sea ice extent have been changing their breeding success at the end of breeding season.  Two papers examining how the decadal decreases in sea ice extent have affected the guillemots’ ability to feed their nestlings were included in a special issue of the journal Progress in Oceanography containing papers generated as part of the Synthesis of Arctic Research (SOAR).  SOAR is an initiative of the National Oceanic and Atmospheric Administration (NOAA) and the Bureau of Ocean Energy Management (BOEM) and seeks to have researchers collaborate on multidisciplinary analyses utilizing complementary data sets.

Two Recent Publications on Cooper Island Research are Now Available

Effects of recent decreases in arctic sea ice on an ice-associated marine bird

by G.J. Divoky, P.M. Lukacs, and M.L. Druckenmiller
Download the full PDF article

This paper examines how changes in sea ice extent and sea surface temperature have affected Black Guillemot prey availability during the nesting period – comparing a historic (1975-1984) period with a recent one (2003-2012).  The graphical abstract below shows how much summer ice has changed over the past four decades. That loss and the concurrent increases in sea surface temperature have reduced availability of Arctic Cod, the guillemots preferred prey, with subsequent decreases in nesting growth and survival. This paper is featured on the Nature Climate Change website.

Graphical abstract draft with chicks and fish labeled and arrows

Change in the Beaufort Sea ecosystem: diverging trends in body condition and/or production in five marine vertebrate species

by  L.A. Harwood, T.G Smith, J.C. George, S.J. Sandstrom, W. Walkusz, and G.J. Divoky
Download the full PDF article

This paper is a synthesis of trends in five species in the Beaufort Sea (bowhead whale, Arctic char, ringed seal, beluga and black guillemots).   While the first two species appear to be benefiting from recent decrease in sea ice, the others are seeing declines in condition, growth or reproduction. This article is available online for the the Progress in Oceanography Journal.

Cooper Island location

Study area and locations from the article. Cooper Island is 40 km southeast of Point Barrow.

This summer we hope to post weekly updates from the field on the guillemots’ breeding success, polar bear visits, and the challenges in conducting research on an isolated island. You may want to bookmark this site if you want to follow how the guillemots are doing as our study enters its fifth decade.

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