Barau’s
Petrel, the easiest Pterodroma in the
world to see
The Ile de Réunion
The
Indian Ocean island of Réunion lies between the islands of Mauritius and
Madagascar with approximately 93 nautical miles (170 kilometres) of sea between
Reunion and Mauritius to the ENE and 360 nautical miles (675 kilometres) NW to
the closest coast of Madagascar. The island is centred at approximately 21°07’
South 55°32’ East.
It
is an overseas département of France,
and hence effectively part of the EU. For European-based Francophile birders
this makes it an attractive option for a short break, a tropical France in the Indian Ocean.
Réunion
is the youngest of an archipelago known as the Mascarene Islands,
which were formed over a part of the Earth’s crust known as the Réunion
hotspot. The oldest islands are now but coral shoals eroded over the last 35
million years while Mauritius
is some 8-10 million years old; Réunion though, has
been formed in the last 2 million years. The island contains three classic
shield volcanoes, formed when lava breaks through the thin oceanic crust. These
include the highest peak, the extinct Piton des Neiges, at 3069 metres, and the
far from extinct Piton de la Fournaise (2631 metres). The latter is one of the
world’s most active volcanoes and has erupted as recently as November 2008.
Figure 1. Lava
flow from 2008 at Pointe du Tremblet, Ile de Réunion.
In
many ways Réunion is very similar to the island
of Hawaii, USA,
(‘Big Island’),
although the latter is larger (Hawaii
is 10432 km² while Réunion is 2512
km²): both were formed in a geologically similar way,
and have very active volcanic areas in their south-eastern quarters. They are
both situated at similar distances from the equator and receive some of the
heaviest rainfall on earth when the moisture-laden trade winds from the east
meet the volcanic mountains. Cilaos, near the centre of Réunion,
has received 1,869.9 mm (73.6 in) of rainfall in 24 hours, this
is the greatest total ever recorded on Earth; other sites on the island have
received 18 metres of rainfall in one
year!
The Petrels of Reunion
This geography is not without importance, and is
mentioned here not just because of its self-evident interest! Geologically young,
volcanic, islands near the tropical boundaries offer terrific opportunities for
petrels, for a whole variety of reasons. Geographical isolation makes mammalian
predators a minimal threat, unless, of course, they find their way to the
island, either via their own agency or a host species; un-eroded vertiginous
topography adds to nesting security and proximity of the sea to these sites
gives them an attractiveness matched only by the sea-cliffs of the temperate
zones. The geographical location of these islands with favoured nesting sites
to sub-tropical feeding areas; down (or up depending on the hemisphere) to 40° makes them favorites for several species.
Réunion
fits the bill for two endemic petrels: the endangered Barau’s Petrel Pterodroma baraui and the critically
endangered Mascarene Black Petrel Pseudobulweria
aterrima. Barau’s is thought to have a world population of around 15,000
with between 3000 and 5000 pairs breeding, the latter is one of the rarest
birds in the world and may have a population reaching 100 pairs.
It is thought that most of these birds (of both species)
nest in the area known as Le Grand Bassin, at an altitude of between 2000 and
2800 metres. This is a spectacular gorge inland from the town of St Pierre and viewable
distantly from the town on a clear day. To see video Click here
Figure 2. Le Cirque de Cilaos, Ile de Réunion. One of the world’s wettest places, a
home
to Barau’s Petrel and all bar one of Réunion’s
endemic landbirds.
Barau’s Petrel is known to breed, and by implication
Black Petrel is thought to breed, in the austral summer with egg-laying probably
taking place in November and hatching up to 55 days later. The fledging period then
takes place between January and May.
For
a detailed discussion of the species’ pelagic distribution, see Stahl and
Bartle. Their surveys showed that Barau’s petrels were present in low numbers
in Réunion waters during the austral winter, but absent
from further south, with occupation of nesting sites beginning in September.
These surveys correlate with casual observations made by visiting birders, a
sample of which is listed below. During the fledging
season however the adults forage to the south of Réunion, up to
41° South to the Southern Subtropical Convergence
Zone. In April adult and juvenile Barau’s Petrels begin to
disperse eastwards into the tropical Indian Ocean
and the last leave in mid-May. At this time over the last two decades many
juveniles have been found grounded by attraction to urban lighting. This is a
significant threat to the species, between 1995 and 2003 between 207 and 791
juveniles have been collected annually by the Société d’Études Ornitholigiques
de la Réunion.
Some
Barau’s Petrel sightings from Réunion gleaned
from internet-based bird reports
|
Dates
|
Site
|
Numbers
|
Source
|
|
August
6/8th 2001
|
St
Etienne river
|
30
|
D.
Van den Schoor
|
|
October
31st 2001
|
St
Denis
|
present
|
R.
Hoff
|
|
August
2002
|
St
Etienne river
|
5
|
P.
Hottola
|
|
September
11th 2004
|
St
Etienne river
|
>
400
|
J.
Jansen
|
|
September
19th 2005
|
St
Etienne river
|
240
|
G.
Westdean
|
|
October
19th 2005
|
St
Etienne river
|
present
|
Birdwatching
breaks
|
Significantly,
there are few reports of counts of Barau’s during the breeding season, this may
largely be due to this also being the (even) wetter part of the year, when it
is additionally much hotter in Réunion, and, to
cap it all, it is the southern cyclone season from January until March. These
factors may deter visiting birders who may be giving greater priority the Island’s
endemic and quasi-endemic landbirds.
Birding Réunion
Readers
may have inferred that Réunion’s weather is diabolical. This is actually
far from the case; although the mountains can be very wet and are best visited
in the northern hemisphere summer which is the dry season in Réunion.
My wife and I visited Réunion for a relaxing week in March 2009, a time I
thought may be good for see Barau’s Petrels and she thought would be good for
reading around the pool. We stayed in St Pierre on the southwestern coast; this
is a town seemingly dedicated for the inhabitants of the capital, St Denis, to
go to at the weekend, and has a thriving bar and restaurant culture. In March
the daily maximum temperature was 30°C, with either a stiff south-easterly
trade wind or a light (and hot) northerly; it didn’t rain in St Pierre while we were there. St Pierre is about 7km
south of the St Etienne estuary, the ‘stake-out’ site for Barau’s Petrels.
Seeing Barau’s
Petrel
I
went seawatching every afternoon for six days, usually from around 4pm until
dark, at around 7pm; but kept a casual eye on the sea most of the time and
ventured out at dawn once when the jet-lag had worn off. I either watched from
the harbour sea-wall or walked for 20 minutes to Pointe au Parc, to the south
of town over the river. While a better sea-watching spot, this was a gathering
point for the local youth, most of whom were friendly enough, but whose
curiosity required engaging as they were somewhat mystified why I was staring
at the sea from their skate-board area.
Figure 3. The
Harbour wall at St Pierre,
Ile de Réunion. Barau’s
Petrels frequently come as close at the breakers and fly inland over the
harbour. Pointe au Parc is in the distance (1km away) over the top of the further
harbour wall which is about 250 metres away.
Barau’s
Petrels were present off-shore usually from 3pm, but in low numbers. On one day
there was a mixed-species feeding ‘kettle’ about 5 km off-shore, containing a
few dozen Barau’s, in the late morning. I saw no birds on the morning I got up
early at 7am.
From
4pm onwards the number of birds off-shore increased, with birds circling round
at sea, but some also coming right in-shore and flying along the surf line.
Many began to move north to (presumably) the St Etienne river mouth, with a
continual stream of birds doing this by 5.30pm. Not all birds moved north
though, from 5.30 pm onwards some would start flying with a rapid wingbeat and
begin to rise up to 300-500 metres above the sea and circle around over the
beach. From this time onward some of these birds would then fly directly inland
over the town toward Le Grand Bassin. We saw several directly overhead over our
hotel during the short dusk period, and even saw one flying inland at 10pm
directly over the harbour.
Numbers
varied from night to night, depending on the wind, but it would be not
unreasonable to estimate that between 250 and 1000 birds per night were present
off St Pierre,
with single scans frequently having 100 birds in them. Michael Brooke suggests
that Pterodroma chicks may be fed
every two or three days, so it is possible to surmise that over 5 days different
adults are being seen every night. In my time at St Pierre this means that I may have seen a
25% of the world breeding population, assuming 500 birds per evening and a
total of 5000 pairs!
It
can be seen from the video [Click here] that Barau’s Petrel is a large Pterodroma with a predominantly pale underwing. It has a similar
wingspan to its nearest genetic relatives Trinidade Petrel, P. arminonjoniana and Kermadec Petrel P. neglecta , but is smaller than both
Dark-rumped Petrels, Galapagos P.
phaeopygia and Hawaiian P. sandwichensis as well as Juan Fernandez
Petrel P. externa. The underwing is
more marked than Juan Fernandez and White-necked P. cervicalis Petrels, but less so than Galapagos and, probably,
Hawaiian. It is most similar to Hawaiian Petrel, and I would personally exercise
great trepidation in separating the pair in a blind photograph competition.
Barau’s probably shows more grey on the head and crown than Hawaiian.
On
Réunion there are no identification issues with
Barau’s Petrel, but observers should be aware of the possibility of seeing
Trinidade Petrels from Round Island, Mauritius, and Soft-plumaged Petrels P. mollis from the temperate Indian Ocean.
Seeing other
seabirds
The
two commonest seabirds, other than Barau’s Petrel, seen whilst seawatching at
St Pierre, were Wedge-tailed Shearwaters
Puffinus pacificus, with typically up
to 250 seen each evening and Common Noddies
Anous stolidus with numbers up to 100
each evening. More interestingly there were usually up to 8 individuals of a
small black-and-white Puffinus
shearwater. These birds were evidently members of the Tropical/Audubon’s
complex but had conspicuously broad dark edges to the underside of the wings as
they made rapid progress past the ‘Wedgies’, low over the sea. Rightly or
wrongly, I have assumed that they were P.
(lherminieri) bailloni, which can be considered a Réunion
endemic, and could be called Baillon’s
Shearwater. There are between 3000 and 5000 pairs. The taxonomy of
“Audubon’s” complex in the Indian Ocean would
best be described as ‘complex’ and not the topic of this piece! Otherwise two
other seabirds were seen, White-tailed
Tropicbird Phaethon lepturus, with
the charming French name of paille-en-queue (straw tail)which can be widely
seen around the coast, and one Lesser
Noddy Anous tenuirostris.
A note on Mascarene
Black Petrel.
There
are at least two records of this species mentioned in trip reports, one of
which is described as being at close range (400 m) at St Etienne River mouth in
August. I had hoped that, at least statistically, I might have a chance of
seeing one, or more, from St Pierre
in March, but to no avail. To use English vernacular, I didn’t get a sniff of
one in over 20 hours of seawatching. Ian Sinclair suggests chartering a
Marlin-fishing sport boat from St Gilles, to the north of St Pierre, this option would only be taken by
a committed group with plenty of money who might still not succeed in seeing
one.
It
must also be emphasized that there are a number of potential confusion species,
these include Great-winged Petrel P.
macroptera, dark morph Trinidade Petrel, Jouanin’s Petrel Bulweria fallax and lastly, but by no
means least, Flesh-footed Shearwater Puffinus
carneipes. Any claim of Mascarene Black Petrel must convincingly eliminate
all these species to maintain credibility.
Travelling to, and
in, Reunion
Réunion
can be reached daily from Paris
and other French cities with Air France or Air Austral. Air Austral also serve South Africa and Australia
and is the main ‘island-hopping’ airline in the western Indian
Ocean.
There
are ferries from Mauritius
in addition to regular flights, but these aren’t timed with the pelagic
enthusiast in mind, leaving at dusk and arriving at dawn.
Réunion
has an excellent bus network, which serves every village. There is an express
network (‘Le Car Jaune’) which runs around the periphery of Réunion
and has one cross island route. We travelled between St Denis, St
Louis, St Pierre and Pointe du
Tremblet by Car Jaune and up to Cilaos from St Louis by local bus. All the endemic
landbirds except Réunion Cuckoo-shrike were seen in the forest around
Cilaos. A taxi might be needed to visit La Roche Ecrite from St Denis for the
Cuckoo-shrike. Car hire is easy, and without problems for those experienced
with France,
however the tortuous mountain roads are, in my view, best experienced when
someone else is driving. If you hear a horn on a mountain bend, it means the
bus is coming round and not stopping! I saw one Réunion Harrier
from a bus under circumstances which would have made it impossible to stop a
car.
It
is a Francophone island, and any attempts to try and speak French are better
than none; visitors may struggle if they can’t read, understand, or speak a
word of French.
Bon
chance!
Peter Fraser
2 The Parade, Truro
Cornwall, TR1 1QE
Ornithological references
Brooke, M. Albatrosses
and Petrels across the World. OUP, 2004
Minatchy,
N. Stratégie de reduction de la mortalité
des petrels induite par les éclairges publics. University of Réunion,
2004.
Sinclair, Ian & Langrand, Olivier. Birds of the Indian Ocean Islands.
Struik, Cape Town,
1998.
Stahl, J.-C. & Bartle J. A. Distribution, abundance
and aspects of the pelagic ecology of Barau’s Petrel in the south-west Indian Ocean. Notornis,
39 211-224.
Also
Société d’Études Ornithologiques at www.seor.fr/index.htm
Text, photographs and video © P. FRASER
