temperatures causing earlier spring snowmelt, allowing for a greater
number of days in which the ground was snow-free and providing
more opportunities for the birds to nest.
After 1990, however, guillemot numbers began to decline again;
the colony is now below one hundred pairs once more and continuing
to fall. Those birds that remain are lighter and thinner; mortality rates
are higher; and the number of immigrant birds from Wrangel Island,
which Divoky believes is the source colony, is dwindling. The cause
once again, Divoky believes, is climate change.
This time, however, the problem is that the same warm tempera-
tures that have melted snow on the ground are also melting sea ice,
which is as important for seabirds such as the black guillemot (which
use it as a place to rest during long flights, and which feed on the Arctic
cod which shelter beneath the floes) as for polar bears, seals, sea lions,
and walruses.
NICEWEATHER FORMOSQUITOES
East of Cooper Island, in the Canadian province of Nunavut, a differ-
ent species of guillemot is also showing the effects of climate change,
in a most unexpected way. Since 1990, Anthony Gaston of the
Canadian Wildlife Service and colleagues have been studying a breed-
ing colony of Brünnich’s guillemots on Nunavut’s Coats Island. The
guillemots have the particular misfortune to be located near an area of
high mosquito abundance, and from 1997 to 1999, note the
researchers, mosquito numbers were so high that more than fifty
mosquitoes at a time would swarm over each foot of the unfortunate
birds. Eventually, the harassment and discomfort became so great that
many of the birds were forced to abandon their breeding sites, where-
upon many of the abandoned eggs were eaten by gulls As a result,
Gaston and colleagues recorded in a 2002 paper in the journal Ibis, the
“proportion of eggs lost was about twice as high, on average, on days
when mosquito abundance was high.” Additionally, evidence from
necropsies conducted on a number of dead adult birds “was consistent
with mortality in response to a combination of temperature and mos-
quito attacks, consequent loss of blood and water (through panting to
102 Kieran Mulvaney