 |
| Clipperton...home to Frigatebirds, Boobies and much more |
What is Clipperton?
Clipperton is an uninhabited atoll in the middle of the Pacific Ocean. It's full of amazing wildlife that is faced with a variety of threats.
What's it all got to do with birds?
One of the areas in which TCP is interested in is the effects of human disturbance on remote places in the World. On TCP's voyage to Clipperton, members looked at how things like plastic pollution, shipwrecks and introduced rats were affecting the native birdlife. See the article below...
How can I follow their progress?
TCP has an excellent facebook page which is regularly updated with news of upcoming events (such as workshops in Mexico City, an upcoming boat tour of Scotland, and future expeditions to Cozumel and South Georgia).
Also on the facebook page, you will also find the Birds of Clipperton Top Trumps series!!
The Birds of Clipperton (full version at
For a rocky, uninhabited atoll lying 1000km adrift of Mexico
in the middle of the Pacific Ocean, Clipperton has a remarkably dramatic
ornithological history. Birds on
Clipperton have faced many threats, yet despite the piles of plastic and
plagues of rats, life thrives. The
island continues to host some of the most important seabird colonies in the
world, and also acts as a stop off ‘staging ground’ for an incredibly wide
variety of migratory ducks, waders and passerines.
Seabird Spectacle
At last count,
Clipperton was home to 25,000 breeding pairs of Brown Boobies and 112,000 pairs
of Masked Boobies. Only Desecheo Island,
Puerto Rico, has held a larger Brown Booby colony, and nowhere comes close to
Clipperton for Masked Boobies. These
numbers are all the more remarkable given that half a century ago, an
introduced population of feral pigs had decimated the populations to under
1,000 pairs of each. Although the
shotgun of American ornithologist Ken Stager solved that particular problem,
Clipperton’s seabirds face a new threat from an invasive species – the
rat.
Following shipwrecks to shark fishing boats, rats (the
downfall of so many island endemics) were introduced to Clipperton at the end
of the twentieth century. Without any
mammalian predators to control the population, they now carpet the island,
feeding along the way on seabirds and land crabs. Some of Clipperton’s smaller seabirds are
particularly vulnerable. Sooty Terns have
already ceased to breed on Clipperton as a result of egg predation, whilst White
Terns and Black Noddies are likely to follow soon. Unfortunately, their growing taste for eggs
isn’t the only threat presented by Clipperton’s rats. Their predation of landcrabs means less crabs
to eat vegetation and the island now supports a variety of alien plant species. The result is less space for ground-nesting
birds, more rats, less crabs, more vegetation, and so on.
All at sea
Clipperton’s
boobies, terns and frigatebirds are at ease riding the waves of the Pacific
Ocean and coming ashore occasionally to try and raise their young. Remarkably, however, Clipperton has also been
a temporary home for over 80 species of North American migrant birds which, to
put it simply, should be nowhere near there.
Such lost souls have included a Purple Gallinule (a clumsy,
dumpy swamp dwelling bird which hardly looks as if it could fly across a garden
pond never mind an Ocean), the bizarrely-named Ovenbird (more at home in the
understory of a Canadian deciduous forest) and a Common Nighthawk (a mysterious
crepuscular insect-eater also known as ‘The Goatsucker’).
|
These individuals turn up in remote areas like Clipperton
usually as a result of their migration ‘going wrong’. They are usually young, inexperienced birds
whose internal navigation system isn’t quite up to scratch. Alternatively, tropical storms or other
adverse weather patterns can disorientate birds and displace them hundreds of
miles from where they should be. Although
most of these wanderers will never make it to where they want to go, stumbling
across an island like Clipperton does offer them the opportunity to rest and
feed up before continuing along their lonely path.
Findings of the
Clipperton Project
The Clipperton Project’s (TCP) recent visit found reasons
for both concern and optimism. Some
places were littered with the corpses of dead seabirds – the shards of plastic
in the decomposing bodies revealing the direct effects of this type of
pollution. Huge water cisterns in old
shipwrecked boats were acting as death traps for other birds. Once they’re inside, there isn’t the space to
get out again. The apparent increase in
abundance of rats on the island gave further cause for worry. At night, lights (if one dared to switch them
on) would reveal a pair of rats in every square metre. Such an incredible density of an introduced
exotic mammal cannot fail to affect the native fauna.
On the bright side, Clipperton’s larger seabirds appeared to
be coexisting peacefully with the rats. The
colonies of Brown, Masked and Red-footed Boobies remain healthy, and
Clipperton’s Frigatebird population has shown remarkable growth. TCP also found evidence of breeding
Red-tailed Tropicbirds, a potential first for the island. Without doubt, there is something to work
with.
The Future
The studies of TCP and others have confirmed that Clipperton
is an extremely special place for birds.
Its seabird colonies are of international importance, and the sheer
diversity of lost migrants that have made Clipperton a temporary home beggars
belief. For Clipperton to remain
special, however, it needs human input of a different kind to that seen in its
past. This means removing plastics and
other pollution instead of adding to it, and eradicating alien pests instead of
introducing more.
Of the 134 bird species that have gone extinct globally in
the last 500 years, predation by introduced rats has accounted for a third of
them. Yet the problem doesn’t have to be
fatal. Eradication programmes on islands
such as New Caledonia have had complete success and breeding bird numbers have
been shown to respond remarkably rapidly.
Birdlife International suggest that a rat eradication program might be
the only way now available to safeguard Clipperton’s incredible seabird
populations.
Clipperton’s birds have shown remarkable resilience to the
threats that they have been presented with.
It is surely time to give them a helping hand.
Further Reading
·
BirdLife International. ‘Rat eradication success
in New Caledonia’ http://www.birdlife.org/community/2011/09/rat-eradication-success-in-new-caledonia/
·
BirdLIfe International. ‘Eradicating introduced
mammals from Clipperton Island led to dramatic recovery from seabirds’ http://www.birdlife.org/datazone/sowb/casestudy/261
·
Howell, S.N.G. et al. ‘North American migrant
birds on Clipperton Atoll’. Western Birds.
·
Pitman, R.L. et al. ‘Clipperton Island: Pig sty,
Rat hole and Booby Prize. Marine Ornithology.
·
Stager, K.E. ‘The Birds of Clipperton Island,
Eastern Pacific’. The Condor.
No comments:
Post a Comment