Bulletin of The British Ornithologists' Club 2010 130(4):286-301
47499910

A new taxon of Collared Petrel Pterodroma brevipes from the Banks Islands, Vanuatu

Vincent Bretagnolle, Hadoram Shirihai
Vincent
Bretagnolle
&
Hadoram
Shirihai
295
Bull.
B.O.C.
2010
130(4)
the
Vanuatu
Petrel
colony
in
March,
apparently
did
not
detect
any
P.
brevipes,
possibly
indicating
that
they
had
not
yet
arrived
at
the
colony.
In
contrast,
most
other
populations
of
P.
brevipes
are
autumn
/
winter
breeders,
sometimes
from
February
/
March
or
even
later.
For
example,
six
chicks
were
collected
in
June
on
Kadavu,
Fiji,
and
one
in
July
on
Tanna,
southern
Vanuatu
(AMNH),
while
a
fledgling
was
collected
in
September
on
Rarotonga,
in
the
Cook
Islands
(National
Museum,
Wellington).
The
breeding
season
on
Aneityum
Island,
southern
Vanuatu,
is
apparently
somewhat
earlier:
those
collected
by
MacGillivray
in
February
were
apparently
already
well
advanced
in
their
breeding
(MacGillivray
1860,
Marchant
&
Higgins
1990,
Brooke
2004).
Watling
(1986)
mentioned
that
the
only
confirmed
breeding
in
Fiji
involves
nests
with
chicks
in
May-June,
with
no
evidence
that
the
species
breeds
year-round.
The
dispersal
range
and
possible
migration
of
P.
b.
magnificens
remain
to
be
elucidated,
but
we
expect
photographic
evidence
to
become
available
concerning
its
occurrence
away
from
the
Banks.
Marine
ecology
and
behaviour.
During
December
2009,
we
carefully
observed
the
foraging
behaviour
of
P.
b.
magnificens.
Unless
feeding,
during
daylight
at
sea
the
taxon
generally
occurs
singly.
However,
the
feeding
behaviour
of
these
small
Pterodroma
off
the
Banks
seems
unique
among
Cookilaria
(and
perhaps
all
gadfly
petrels),
as
they
form
sparse
aggregations,
almost
invariably
in
association
with
mixed
feeding
frenzies
of
Legends
to
plates
on
facing
page
Figures
4-7.
Plumage
variation
in
Collared
Petrel
Pterodroma
brevipes
off
Gau,
Fiji
(upper
four
images,
from
left
to
right):
'pure
white'
the
palest
and
cleanest
white
example,
note
the
well-developed
white
supercilium
but
narrowest
dark
underwing
bar;
'grey
peppering'
blotchy
underparts
due
to
(highly
variable)
dark
mottling
and
dappling,
but
belly
predominantly
white
(birds
of
the
last
two
categories
dominate
in
nominate
P.
brevipes
but
are
absent
in
P.
b.
magnificens);
'smoky'
dusky
grey
wash
with
ground
colour
still
paler
than
next
category
and
usually
appears
faintly
blotched
below,
but
dark
breast-band
distinctive
(frequent
in
all
P.
brevipes
but
lacking
in
P.
b.
magnificens
other
than
three
borderline
cases);
and
'dark
grey'
the
usual
darkest
example
found
in
Fiji
(even
darker
birds
are
extremely
rare)
(Hadoram
Shirihai,
©
Tubenoses
Project)
Figures
8-11.
Plumage
variation
in
P.
b.
magnificens
off
the
Banks,
northern
Vanuatu
(lower
four
images,
from
left
to
right).
'Dark
grey'
left-hand
two
birds
(Fig.
8-9),
such
dark
examples
are
virtually
identical
to
nominate,
with
rather
mid
/
dark
and
uniform
grey
underparts,
and
dark
breast-band
strongly
reduced,
but
most
P.
b.
magnificens
tend
to
have
less
white
in
underwing.
'Extreme
dark
grey'
right-hand
two
birds
(Fig.
10-11),
represents
the
darkest
category
(and
matches
the
holotype
of
P.
b.
magnificens),
but
in
these
waters
even
darker
birds
are
observed.
In
particular,
note
the
very
dark
underparts
with
virtually
no
darker
breast-band
and
very
dark
underwing
with
only
small
pure
white
areas
on
the
innerwing-coverts
and
larger
median
coverts,
while
the
dark
underwing
bar
almost
encompasses
half
the
wing's
width
(the
broadest
in
any
gadfly
petrel)
this
type
is
found
in
c.42%
of
P.
b.
magnificens
off
the
Banks,
but
birds
partially
approaching
it
number
c.2%
off
Gau,
Fiji.
Collectively,
'dark
grey'
and
'extreme
dark
grey'
birds
comprise
c.90%
of
P.
b.
magnificens
off
the
Banks,
the
other
10%
are
still
quite
dark,
whereas
in
all
other
populations
of
P.
brevipes
the
dark
morph
represents
at
most
17%
of
birds
(see
text
and
Table
2).
Note
that
the
bird
in
Fig.
8
was
the
palest
P.
b.
magnificens
observed
off
the
Banks,
considered
borderline
between
'smoky'
and
'dark
grey'
plumage
types.
Such
birds
and
the
'dark
grey'
type
compromised
c.58%
of
P.
b.
magnificens,
which
are
identical
in
plumage
to
the
darkest
examples
of
dark-morph
P.
brevipes
in
other
populations
(Hadoram
Shirihai,
©
Tubenoses
Project).
At
sea,
it
is
very
difficult
to
evaluate
the
precise
extent
of
grey
and
white
/grey
areas
in
the
underwing-
coverts,
or
the
width
of
the
diagonal
bar.
And,
in
photos
their
appearance
varies
with
the
angle
and
light,
and
several
images
will
be
needed
to
reliably
evaluate
these
features.
We
do
not
recommend
attempting
to
identify
P.
b.
magnificens
away
from
its
presumed
breeding
area.
Figure
12.
Magnificent
Petrel
Pterodroma
brevipes
magnificens,
in
typical
low
flight
note
that
when
sunlit
the
dark
blue-grey
underparts
appear
warmer
and
rustier
brown.
This
bird
belongs
to
the
'extreme
dark
grey'
type
(found
in
c.42%
of
P.
b.
magnificens
off
the
Banks).
Note
the
extremely
limited
pure
white
on
the
underwing,
with
small
white
innerwing-coverts,
while
the
dark
underwing
bar
is
very
broad
(Hadoram
Shirihai,
©
Tubenoses
Project)
Figure
13.
Vanua
Lava
(the
presumed
breeding
island
of
Magnificent
Petrel
Pterodroma
brevipes
mag?tificens)
from
the
north,
showing
its
two
volcanic
cones
(Hadoram
Shirihai,
©
Tubenoses
Project)