Bulletin of The British Ornithologists' Club 1995 115:75-87
40028842

A new species of Puffinus shearwater from the western Indian Ocean

H.
Shirihai
et
al.
78
Bull.
B.O.C.
1995
115(2)
whiter
shades
to
the
basal
outer
webs
of
the
outer
primaries;
axillaries
white.
Bare
parts.
Bill
proportionally
relatively
long
(i.e.
relatively
longer
than
assimilis)
and
typically
slender
with
poorly
developed
nasal
tubes
and
maxillary
unguis,
bluish-grey
with
blackish
shade
on
culmen
ridge.
Legs
(colours
recorded
when
alive):
inner
tarsus,
two
inner
toes
and
webs
bluish-grey
(top
half
of
outer
tarsus
on
specimen
appears
similarly
pale),
remainder
of
legs
and
feet
black.
Measurements
of
holotype
(mm).
Wing
204.5
(maximum
chord);
tail
78;
bill
28
(culmen
from
feathers),
34
(from
skull),
20.5
(from
anterior
nostril
to
bill
tip);
tarsus
40.
Measurements
of
other
individuals
(mm)
.
Juvenile
at
point
of
fledging,
male,
undated,
L'ile
de
la
Reunion,
BM
(NH)
reg.
no.
1866.
7.
21.
10,
purchased
from
Maison
Verreaux.
Wing
162
(visible
primaries
7—10
growing),
tail
74
(very
abraded),
bill
28.5
(culmen
from
feathers),
35
(from
skull),
tarsus
39.
Resembles
holotype
(including
similar
shape/pattern
of
dark
and
light
areas
of
bill/legs),
but
upperparts
differ
in
duller
blackish-brown
appearance.
The
advanced
stage
of
juvenile
plumage
suggests
collection
on
or
near
the
breeding
area.
English
name.
We
suggest
Mascarene
Shearwater,
after
the
oceanic
Mascarene
ridge
which
may
form
part
of
the
breeding
range.
Additional
characters
(from
similar,
live
birds).
Although
Audubon's
and
Little
Shearwaters
are
superficially
rather
similar
to
our
new
species
in
plumage,
there
are
also
important
differences
in
structure,
proportions
and
movement.
On
the
water
and
in
flight,
atrodorsalis
appears
intermediate
between
Manx
(but
obviously
distinctly
smaller)
and
Little
(races
assimilis,
baroli,
tunneyi,
but
obviously
larger
than
these).
In
size,
it
may
approach
the
Southern
Oceans
race
elegans
of
the
Little
Shearwater,
but
its
general
appearance
is
slimmer
(i.e.
proportionally
more
slender-billed,
longer-winged
and
longer-tailed),
and
it
has
the
more
black
and
white
appearance
of
the
Manx
Shearwater.
The
flight
action
is
also
intermediate:
in
calm
weather
it
flies
with
rapid,
almost
whirring
shallow
wing-beats
(although
not
as
fast
as
Little),
interspersed
with
frequent
glides
and
shears,
fairly
close
to
the
surface
(even
in
a
wind-force
of
2—4);
in
stronger
winds
it
arches
higher,
but
its
travelling
flight
is
rarely
as
powerful
or
sustained
as
Manx.
Individual
variation.
The
few
specimens
that
we
have
been
able
to
examine
in
the
hand
or
observe
closely
in
the
field
show
that
there
is
a
small
amount
of
individual
variation;
e.g.
the
pectoral
patches
(the
dark
feathers
running
down
the
neck
sides)
are
moderately
developed
and
rather
distinct
in
the
Eilat
bird
and
the
Reunion
specimen,
but
are
smaller
in
the
bird
captured
in
Durban
in
1981
and
poorly
developed
in
the
Durban
specimens
of
1987.
The
demarcation
of
the
hood
below
the
eye
also
varies;
it
is
clear
cut
in
the
1987
Durban
individual,
moderately
so
in
the
1981
individual
and
the
Reunion
specimen,
and
somewhat
ill-defined
in
the
Eilat
individual.
The
lack
of
sharpness
in
the
latter
was
discussed
in
Shirihai
&
Sinclair
(1994)
and
attributed
to
the
bird's
active
body
moult.