Petrel
expert Nicholas Carlile of the Department of Environment and Climate
Change in New South Wales in Australia and Bermuda Conservation Officer
Jeremy Madeiros with a cahow on Nonsuch Island. (Photos by Chris Burville)
This year, a
likely reason for the survival success of the cahow has been discovered
by the work of the Conservation Officer and his team.
He
said: “The cahows have this extraordinary ability we have tracked them
travelling 4,500 miles to feed their chicks once; they have gone to
Nova Scotia, Newfoundland and the mid-Atlantic ridge. We are finding
that the cahow can go thousands of miles to find food.
“They
are foraging all the way up to the edge of the pack ice in the St.
Lawrence. That’s why we think the food for the chicks when they first
hatch is krill, from places with very cold water temperatures.
“It is a speciality for them, right after they hatch, and then they switch to squid and fish.”
He
explained the parent birds entirely act on instinct to seek out the
krill, and so follow the winds to these northern latitudes.
He
explained that while they were aware that cahows do fly hundreds of
miles to their feeding grounds and don’t spend much time in Bermuda,
until the last year there was very little knowledge about their
movements.
“We
knew they feed off the Carolinas, 600 miles away at the closest point,
and otherwise, 200 miles east of Cape Cod, and in Canadian waters.”
He
noted: “It is the Holy Grail the pinnacle for bird watchers in that
area to see a cahow, because it has been spotted on average just once
every three years.”
But
the conservation team have now discovered the cahows are going much
further than that. “These birds are using storms to sling-shot them on
their way that wind is raw, free energy.
“We
have been able to confirm that they will catch a free ride on a
south-westerly wind, ahead of the storm, which will shoot them
north-easterly out and up into the Atlantic,” said Mr. Maderios.
“In some cases, we have recorded them travelling 450 miles in a day at this rate they could cross to the US in a day and a half!
“The
secret is, they catch a ride on these storms’ free wind to their
feeding grounds, near the Azores or the Grand Banks, to forage while
the storm passes.
“Then,
behind the storm, there are north-easterly strong gale force winds, so
they hitch a ride on those winds straight back to Bermuda!”
The first indications that the cahows were travelling these great distances first were discovered two years ago.
It
was in January 2009 that petrel expert Nicholas Carlile of the
Department of Environment and Climate Change in New South Wales in
Australia came to Bermuda to help set up the data logger aspect of the
cahow project, affixing tiny location detection devices to the birds
and then downloading the information when the loggers were retrieved.
“The
Australians couldn’t believe the distances it’s the same kind of
distances the albatrosses are doing and these birds are a quarter of
the size.”
The distances were so great that the conservation officer felt it was important to double check the results.
“We
were suspicious when we got the first tags back, so we put the word out
to Canadian fishermen and others in the northern regions where the
cahows were being logged.”
They duly received reports that they were occasionally being seen in those areas.
“We
thought the bird might have been confused with other petrels. But when
we got a photograph, it was unmistakeably a cahow. So we know, every
year, they go up to Canadian waters.”
He said: “We’ve now been able to follow nine birds for a year or more one for two years.
“We
have found, from those nine birds, that the minimum distance in 12
months is 36,000 miles; that is, taking the fixed recorded points in a
straight line.
“The
champion went 81,000 miles the equivalent of four times around the
equator. It is an unbelievable distance. They can go anywhere they
want. We’ve had a couple go fairly close to the Canary Islands.
“Of the nine, two thirds of them spend the summer near the Azores. That was a surprise, that there was this Azorean connection.
“We
think they go to that part of the Atlantic because that’s where shrimp
spawn. In fact, sperm and beaked whales also go there to feed.
“But, a third of the birds stayed between Bermuda, Nova Scotia and North Carolina. They spent the whole year in that area.
“Some
birds may spend the summer in different areas. Some seem to prefer to
go further distances, while others like to stay closer to home. So it
seems to be a personal preference.
Summarising their findings, he said: “We’ve discovered an increase in their range by 20-fold, to a million or so square miles.
“We
now know they forage along the coast of Western Europe, across the
entire North Atlantic 4,000-5,000 miles. We are still catching our
breath over this.
“We
have recorded one bird that went almost as far as Ireland, and then to
Spain and Portugal and France we’ve now got birders who want to go out
and look for them from Ireland. They can exploit food resources across
the entire Atlantic.”
“We are now using smaller tags to see if the same birds go to the same places or not. We’ve raised a lot of new questions.
The cahow is a creature of the north Atlantic a true Bermudian, because he loves to travel to exotic places.
The
cahow’s ability to survive while at sea is greatly enhanced by the fact
that they are able to travel such enormous distances.
It
means that if a food source is not available in one region of the
Atlantic: “… they can move somewhere else,” said Mr. Maderios. “It
bodes well for their survival it is not like they’re stuck within a
couple of hundred miles.”
Although
the results gathered from the data loggers have been remarkable, these
birds are in fact constructed perfectly for this sort of extreme flight.
“The
design of the bird the wings compared to body size are the longest
wings of any sort of bird species, so the wing load is very light,
meaning they use a minimum of effort to stay in the air. They use only
nine to 13 percent of the energy of a gull, for example,” he said.
“Over
the open water, they glide at high speed, and very low then dive into
the trough of a wave where there is no wind, and then pull up and over
the crest of the wave.
“They
are hit in the face by the wind, so they gain height, but lose speed.
Then, they dive into the trough of the wave again, gain speed and lose
height they do this ballet for hundreds of miles.
“They
are like the albatross in the southern oceans; but while they are like
the fighter jets of the sea bird world, the albatross is the B52 bomber.
“Cahows definitely have the best design for going fast over long distances with the minimum expenditure of energy.”
Australian
petrel expert Nicholas Carlile, who brought his expertise to the cahow
relocation project in the aftermath of Hurricane Fabian in 2003, came
back in Bermuda two years ago, bringing with him the tools to help
answer the question of where the cahow goes during its many months at
sea.
Mr.
Carlile has been involved in seabird and island research for more than
20 years with the Department of Environment and Climate Change in New
South Wales in Australia.
During his three week visit here he and Conservation Officer Jeremy Madeiros fixed pea-sized data loggers to 12 cahows.
This tiny and sophisticated piece of equipment collects location information and stores it while the bird is at sea.
Upon
the bird’s return the logger is removed from the bird, and the
information stored on them is downloaded to tell scientists in general
terms where and on what routes the birds travel when they leave their
burrows.
Nonsuch
Island in Castle Harbour, which has been returned to its endemic
origins, has taken a further big step back to those roots.
The
cahow has officially established a colony there with a new chick,
called Bermudiana, having been successfully raised by its parents from
egg to fledgling.
Bermudiana
was named after one of the babies that were born here while the Sea
Venture passengers and crew were stranded on the Island’s shores and a
very few years before the very last cahow chick fledged from Nonsuch.
The
first chick, born to the same parents as Bermudiana, required some
assistance from Mr. Maderios in order to successfully fledge, had been
called Somers, after the flag ship Sea Venture’s Admiral Sir George
Somers. “So we have a Sea Venture theme,” he noted.
“We
had three pairs that did lay eggs but they did not hatch, which is very
common because these first-time parents are inexperienced. So truly,
100 percent, Bermudiana was the first.
The
year, the new breeding season has already started. “We are going from
strength to strength,” said Mr. Maderios. “We’ve got eight pairs
established in nest burrows and another five nests which are being
prospected by young male cahows, who then spend the next year or two
attracting a mate.
“So, we’ve got 13 burrows with cahows in them. Already, we have more than enough.
“Of
the chicks we have translocated to Nonsuch over the last decade or so,
102 chicks fledged out to sea, and we have had a 20 percent success
rate already with 12 of 21 returns, which is a 60 percent survival rate.
“We
are also preparing the ‘b’ nesting site on Nonsuch Island so the cahows
will have two foot-holds there. The two sites should eventually merge
and make one colony.
“I’ve
always believed you don’t put all your eggs in one basket. We had a
lightening strike in 2006, which killed a casurina tree. The shock
could have affected any chicks in the burrows. It’s better to have a
second site it’s insurance, basically,” he explained.
Another reminder of the wisdom of this philosophy was Bermuda’s recent brush with Hurricane Igor.
“That
hurricane didn’t cause any thing like the damage that Fabian caused.
However, one of the nesting islands has become two islands, and all the
islands lost big chunks.
“It reinstilled the need to relocate them from these vulnerable spots. It was another wake up call.
“Certainly,
climate change is affecting the integrity of the structures, and that’s
the real fear a couple of those islands may not be here any more after
another bad storm.
“At least now there is an alternate place that’s safe from this sort of erosion for thousands of years.”
“The programme is important to educate the Bermuda public about it is our natural heritage.
“It
is hugely important internationally we are held up internationally for
our environmental initiatives the turtles, the tropic birds and our
coral reef protection.
“We are held up as an example of what should be done.”
