http://news.independent.co.uk/uk/environment/story.jsp?story=347187
Antarctica's hungry birds seek shelter off Britain
By Brian Unwin
30 October 2002
We knew they wandered, but not this far. In a series of phenomenal journeys, the
seabirds of the Southern Ocean, of Tristan da Cunha and the Falkland Islands and
Antarctica, are coming to Britain and the north-east Atlantic in increasing
numbers.
Their unprecedented trips to the opposite end of the globe may be linked, some
scientists think, to climate change and its effect on the productivity of
plankton and the organisms at the bottom of the food chain.
Great shearwaters, which should be back at their breeding colonies at Tristan da
Cunha and Gough Island in the middle of the South Atlantic, 6,000 miles away,
have this month been gathering off the Isles of Scilly; more than 300 have been
seen.
Sooty shearwaters, the nearest colonies of which are on the Falkland Islands
7,000 miles away, flocked to the North Sea in record numbers during September.
Watchers counted 1,000 to 2,600 birds on 22 September.
And tiny Wilson's petrels, which nest on rocky, ice-free coasts of Antarctica
and offshore islands 8,000 miles away, and were virtually unknown in British
waters 20 years ago, have been recorded on many days between late June and
September.
As well as sightings off the more expected south-westerly locations such as the
Isles of Scilly, Cornwall, Clare and Kerry, one was discovered 15 miles from
Blyth, Northumberland, the first recorded off eastern Britain.
Black-browed albatrosses, which never normally fly north of the Equator,
continue to be reported around Britain despite a declining world population. One
was seen off St Kilda, the remotest of the Western Isles, in June, and another
off Spurn at
the mouth of the Humber last month.
The red-billed tropicbird, which nest on islands off west and north-west Africa,
was recorded for the first time in British waters in 2001 off south-west
England. This year there were more sightings in the same area during March and
April. Fea's
petrels, which also nest on Atlantic islands off north-west Africa, are showing
up more often. During September they were seen off the Yorkshire, Durham and
Northumberland coasts, Scilly, Orkney and Cork.
One reason for the numbers may be better bird-watching at sea. But Professor
Dick Veit, an expert on climatic effects on seabird movements, believes there
could also have been southern ocean climatic factors. Professor Veit, of the
City
University of New York, told The Independent: "There is substantial evidence
from California waters and also from breeding grounds in New Zealand that sooty
shearwaters declined by up to 90 per cent during 1987-1995. This is closely
linked to the warming of the oceans. Such warming, and consequent reduction of
planktivorous foods, might well also lead to increased dispersal and thus
increased incidence in British waters."
The black-browed albatross, great shearwater and Wilson's petrel fed in
Antarctic and sub-Antarctic waters in the breeding season, he added. "Those
oceans have warmed in the past 30 years, and it is likely that plankton
populations have declined.
Whether such a shortage of food would prompt exaggerated northwards dispersal is
worth considering.
"For black-browed albatrosses, we have data, based on satellite-tracking, that
they respond to a shortage of food by dispersing greater distances. "
He said UK sightings of Fea's petrel and tropicbird were harder to explain
because less climate change data had been collected in the tropical Atlantic.
"But in the Pacific, tropical seabirds have been covering vast distances after
catastrophic
breeding failures associated with El Niño events."
Professor Bob Furness, a seabird expert at Glasgow University, said: "Dick's
speculations are reasonable enough, but they are largely speculation. It would
be worth studying whether plankton densities have decreased through the
Southern Ocean
and whether that is due to warming. I'm not aware of compelling evidence.
"But his point that birds disperse further if food supply is reduced is well
made, and certainly true. Lots of studies show that."
Birding-Aus is on the Web at
www.shc.melb.catholic.edu.au/home/birding/index.html
To unsubscribe from this mailing list, send the message
"unsubscribe birding-aus" (no quotes, no Subject line)
to
|
