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Pyle et al.: Bryan’s Shearwater in Midway Atoll 5
Marine Ornithology 42: 5–8 (2014)
INTRODUCTION
A new species of Procellariiforme, Bryan’s Shearwater Puffinus
bryani, was described by Pyle et al. (2011) based on a specimen
collected by one of us (ABA) on 18 February 1963 on Midway
Atoll, Northwestern Hawaiian Islands. At the time it was described,
its breeding location was unknown, but subsequent documentation
of specimens from the Bonin (Ogasawara) Islands, Japan, indicates
that breeding likely occurs during winter in these islands (Kawakami
et al. 2012). Given the infrequency of records, it is undoubtedly a
rare bird (Pyle et al. 2011), and additional information on its
natural history and breeding requirements is needed to promote its
conservation (Kawakami et al. 2012).
Here we document a second Bryan’s Shearwater from Midway
Atoll, recorded during the winters of 1990/91 and 1991/92.
We describe the habitat in which the shearwater was found
and provide a detailed analysis of its vocalizations. We also
provide more detail on the circumstances, location and habitat
in which the first (type) specimen was collected in 1963, and
we review at-sea records of small shearwaters in the central and
eastern North Pacific Ocean, as these may pertain to the pelagic
distribution and foraging habitat of this species. The information
we provide is applicable to the taxonomy, future monitoring and
conservation of Bryan’s Shearwater.
RESULTS
The second Bryan’s Shearwater from Midway Atoll was initially
heard vocalizing from a crevice by US Fish and Wildlife Service
(USWFS) personnel (D. Williamson, in litt.) on unspecified dates in
December 1990 and January 1991. The location was at the extreme
east-northeast corner of Sand Island (Fig. 1). It was not heard again
until an unspecified date in early to mid-December 1991, when the
same vocalizations were heard from the same vicinity by USFWS
personnel. On 17 December 1991, two of us (RD and BDE)
audiotaped the vocalizations, captured the bird, and videotaped
and photographed it before returning it to the crevice. It was heard
again by USFWS personnel calling from the same crevice on 1
January 1992 (M. Naughton, E. Flint, in litt.), the last documented
observation. The shearwater was vocalizing from an accumulation
of artificial concrete and coral rubble installed to shore up a metal
retaining wall (Fig. 2A). The bird was captured and returned from
a crevice about 0.5–0.7 m below the surface and against the metal
wall. Video of the shearwater, burrow and surrounding habitat, can
be viewed at http://www.birdpop.net/index.php/en/brys.
The shearwater was small and showed plumage and soft-part
characters very similar to the type specimen and those from
the Bonin Islands (Pyle et al. 2011, Kawakami et al. 2012),
including dark slate upperparts, white in the face extending
SECOND RECORD OF BRYAN’S SHEARWATER PUFFINUS BRYANI
FROM MIDWAY ATOLL, WITH NOTES ON HABITAT SELECTION,
VOCALIZATIONS AND AT-SEA DISTRIBUTION
PETER PYLE1, REGINALD DAVID2, BRUCE D. EILERTS3, A. BINION AMERSON4,
ABRAHAM BORKER5 & MATTHEW MCKOWN5
1The Institute for Bird Populations, PO Box 1346, Point Reyes Station, CA 94956, USA (ppyle@birdpop.org)
2Rana Productions, 75-5815 Kini Loop, Kailua-Kona, HI 96740, USA
3The Sandberg Group, Inc., 14565 Valley View Ave., Santa Fe Springs, CA 90670, USA
413723 Littlecrest Drive, Dallas, TX 75234, USA
5Coastal Conservation Action Lab, University of California Santa Cruz, 100 Shaffer Road, Santa Cruz, CA 95060, USA
Submitted 27 September 2011, accepted 8 October 2013
SUMMARY
PYLE, P., DAVID, R., EILERTS, B.D., AMERSON, A.B., BORKER, A. & McKOWN, M. 2014. Second record of Bryan’s Shearwater
Puffinus bryani from Midway Atoll, with notes on habitat selection, vocalizations and at-sea distribution. Marine Ornithology 42: 5–8.
Little is known about the conservation requirements of Bryan’s Shearwater Puffinus bryani, first described in 2011 based on a specimen
collected in February 1963 near an area containing concrete rubble at Midway Atoll. Here we document a second Bryan’s Shearwater
observed on Midway during the winters of 1990/91 and 1991/92. It was vocalizing from a 0.5–0.7 m crevice within an accumulation of
artificial concrete and coral rubble. Recent winter specimens of Bryan’s Shearwaters from the Bonin (Ogasawara) Islands, Japan, were also
collected in areas with rocky crevices, possibly burrows they co-utilize with summer-breeding Bulwer’s Petrels Bulweria bulwerii. This
habitat is not found naturally on low-lying atolls in the Northwestern Hawaiian Islands; however, it does occur on Nihoa and Necker Islands,
where Bulwer’s Petrels breed abundantly. Digitized video and vocalization recordings from 1991 on Midway, detailed here and available
at http://www.birdpop.net/index.php/en/brys, are currently being used to locate breeding Bryan’s Shearwaters in the Bonin Islands. Similar
monitoring should be considered for Nihoa and Necker Islands. None of five at-sea records of small shearwaters in the central and eastern
North Pacific Ocean can be confirmed as Bryan’s Shearwater; thus, nothing is currently know of its life history or requirements at-sea.
Key words: breeding habitat, conservation, Puffinus bryani, taxonomy, vocalizations
5
6 Pyle et al.: Bryan’s Shearwater in Midway Atoll
Marine Ornithology 42: 5–8 (2014)
above the eye, largely white underparts and underwing, and dark
undertail coverts with white tips on some lateral feathers (Fig. 3.,
http://www.birdpop.net/index.php/en/brys). These characteristics
are unique to Bryan’s Shearwater and confirm the identification
(Pyle et al. 2011).
Fig. 1. Observation locations of Bryan’s Shearwaters on Sand
Island, Midway Atoll, in 1963 and 1990–1992.
Fig. 2. Crevice in which Bryan’s Shearwater was observed in
1990–1992 (A), and habitat in which Bryan’s Shearwater specimen
was collected in 1963 (B). Photos: Reginald David (A) and
A. Binion Amerson (B).
A
B
Fig. 3. Bryan’s Shearwater, Midway Atoll, 17 December 1991.
Photos: Reginald David.
Fig. 4. Spectrograms of Bryan’s Shearwater Puffinus bryani
(A, Midway Atoll, this paper), Boyd’s Shearwater P. boydi
(B, Cape Verde islands, M. Robb, pers. comm.), Barolo Shearwater
P. baroli (C, Azores islands, M. Robb, pers. comm.), Little Shearwater
P. assimilis haurakiensis (D, Burgess Island, C. Gaskin, pers.
comm.) and Newell’s Shearwater P. newelli (E, Kaua’i island,
A. Raine, pers. comm.). Digital audio representations of these
calls can be found at http://www.birdpop.net/index.php/en/brys
(spectrograms created with WildSpectra).
A
B
C
D
E
Pyle et al.: Bryan’s Shearwater in Midway Atoll 7
Marine Ornithology 42: 5–8 (2014)
The recorded vocalizations of the Bryan’s Shearwater consist of a
series of five to nine call phrases repeated over approximately 7 s.
The most typical call phrase contains six cadenced, high-pitched
call notes, repeated over a course of approximately 1 s (Fig. 4A,
Table 1). Phrases begin with a high-pitched, noisy note and fall
and rise consistently through the length of the phrase (Table 2).
The higher pitch and longer duration of some of the notes indicate
that the captured shearwater was most likely a male (Robb et al.
2008; M. Robb, pers. comm.). The vocalizations are generally
similar to those of other small shearwaters, with call structure,
tempo and rhythm resembling those of Newell’s Shearwater
P. newelli more than those of phenotypically similar small
shearwaters including P. boydi, P. baroli and P. assimilis (Fig. 4,
http://www.birdpop.net/index.php/en/brys). This may support
molecular taxonomic evidence placing Bryan’s Shearwater in a
clade that includes Newell’s but not these other shearwaters (Pyle
et al. 2011).
The type specimen of Bryan’s Shearwater collected in 1963 was
an individual found atop a sand dune, not in a burrow as reported
by Pyle et al. (2011). The area in which it was collected was near
the northernmost reach of Sand Island, along its central north coast
(Fig. 1). At the time of collection, the sand dunes provided a barrier
between the beach and an inland protected area that was vegetated
with Scaevola sericea bushes and contained wooden structures and
concrete debris (Fig. 2B). Based on the habitat in which the second
bird was found, the 1963 bird was likely prospecting the general
area when found atop the sand dune.
There have been five reports of Little Shearwater P. assimilis in the
North Pacific Ocean that may have been Bryan’s Shearwaters, as
the two species are similar in appearance, and identification criteria
for Bryan’s Shearwaters were unknown at the time. However,
a review of these records reveals none that can be confirmed as
Bryan’s Shearwater. A specimen of a Procellariiforme collected
in the Marshall Islands in 1964 was initially identified as a
Little Shearwater (Amerson 1969) but has been re-identified as
a Stejneger’s Petrel Pterodroma longirostris (Clapp 1984). Little
Shearwaters reported 12 October 1997 in the Gulf of Alaska (Day
2006) and 29 October 2003 off Monterey, California (CBRC 2007),
were of individuals with white undertail coverts, excluding Bryan’s
Shearwater for these records. Small shearwaters reported 26 August
1996 near Kodiak Island in the Gulf of Alaska (Day 2006) and 25
August 2010 near the Hawaiian Islands (M. Force, in litt.) were
not described in enough detail to identify them to species. Thus,
the only confirmed at-sea record of Bryan’s Shearwater to date is
of one photographed 15 September 2009 near the Bonin Islands
(Chikara 2009), possibly in transit. Therefore, nothing is currently
known of the at-sea range or ecological foraging requirements of
Bryan’s Shearwater.
DISCUSSION
The habitat in which the two Bryan’s Shearwaters were found on
Midway Atoll accord with that in which four of six specimens were
found in the Bonin Islands (Kawakami et al. 2012), consisting of
rocky areas covered in some places by dense vegetation. One of
the six Bonin specimens was found in a shallow crevice on a rocky
cliff where Bulwer’s Petrels Bulweria bulwerii breed in summer.
The Bryan’s Shearwater documented in 1991 on Midway was in a
crevice located 0.5–0.7 m deep in rocky habitat, suggesting that this
might be typical breeding habitat for the species. This habitat is not
natural on Midway, which, without human alteration, would consist
solely of sandy substrates and low vegetation, as is typical of atolls
in the Northwestern Hawaiian Islands (Amerson 1971, Woodward
1972). While it is possible that Bryan’s Shearwaters may also breed
in burrows or under dense Scaevola bushes, the lack of any other
records during extensive biological investigation on Midway and
other low-lying atolls in the Northwestern Hawaiian Islands during
the 1960s (Amerson 1971, Woodward 1972) indicates that they do
not breed regularly on these atolls (Pyle et al. 2011).
Copies of the vocalizations of the Bryan’s Shearwater from 1991 are
available at http://www.birdpop.net/index.php/en/brys. Recorded
and digitized vocalizations such as these are of great value for
automated acoustic surveys to monitor presence and abundance
of seabirds in remote locations (Buxton & Jones 2012), and for
the conservation of seabirds (Croxall et al. 2012). Passive acoustic
sensors are currently being deployed in the Bonin Islands and on
TABLE 2
Measurements of Bryan’s Shearwater note parameters (from call phrases containing six notes)
Parameter Note 1 Note 2 Note 3 Note 4 Note 5 Note 6
Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD
Note length (s) 0.28 (0.02) 0.14 (0.01) 0.12 (0.01) 0.13 (0.01) 0.11 (0.01) 0.35 (0.01)
Peak frequency (Hz) 3101 (457) 2256 (876) 2955 (819) 2078 (607) 2961 (698) 1943 (579)
Harmonic interval (Hz) 1598 (1284) 1898 (433) 1534 (641) 1882 (421) 1594 (658) 1781 (450)
n = 15 n = 16 n = 16 n = 16 n = 16 n = 16
TABLE 1
Characteristics of Bryan’s Shearwater calls
recorded on Midway Atoll
Parameter Mean SD n
Calls
Call length (s) 6.94 0.77 5
Notes per call 33.00 2.00 5
Notes/s (call) 4.55 0.25 5
Phrases
Phrases per call 6.80 0.84 5
Phrase length (s) 1.07 0.32 32
Notes per phrase 5.13 1.72 32
Notes/s (phrase) 4.79 0.74 32
8 Pyle et al.: Bryan’s Shearwater in Midway Atoll
Marine Ornithology 42: 5–8 (2014)
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CHIBA, H. & HIRAOKA, T. 2012. Bryan’s Shearwaters have
survived on the Bonin Islands, Northwestern Pacific. Condor
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PYLE, P., WELCH, A.J. & FLEISCHER, R.C. 2011. A new
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Midway Atoll to monitor Bryan’s Shearwaters and other breeding
seabird species. Rocky habitats in the Northwestern Hawaiian
Islands, such as those on Nihoa and Necker Islands (Clapp &
Kridler 1977, Clapp et al. 1977), may provide more suitable
breeding habitat for Bryan’s Shearwater. Bryan’s Shearwaters most
likely breed in winter (Pyle et al. 2011, Kawakami et al. 2012, this
paper), and they may co-utilize breeding sites of Bulwer’s Petrels
at Nihoa, Necker, or other Hawaiian islands on which Bulwer’s
Petrels breed abundantly in summer. Listening devices should be
considered on these islands to monitor for Bryan’s Shearwaters. We
also encourage researchers at sea in the Pacific to be aware of and
look for Bryan’s Shearwaters, so that more can be learned about
their foraging requirements.
ACKNOWLEDGEMENTS
We thank United States Fish and Wildlife Service personnel,
including Don Williamson, Beth Flint and Maura Naughton,
for first detecting the Bryan’s Shearwater in 1990 and for
information regarding its presence. We thank Abram Fleishman
and Christopher Tarango for help with call measurements; Chris
Gaskin, Magnus Robb, Nick Holmes, and Andre Raine for
assistance with and permission to exhibit shearwater recordings;
and Joanna Wu for help with Figure 1. This is publication 468 of
the Institute for Bird Populations.
REFERENCES
AMERSON, A.B. 1969. Ornithology of the Marshall and Gilbert
Islands. Atoll Research Bulletin 127: 1–348.
AMERSON, A.B. 1971. The natural history of French Frigate
Shoals, Northwestern Hawaiian Islands. Atoll Research Bulletin
150: 1–383.
BUXTON, R.T. & JONES, I.L. 2012.Measuring nocturnal seabird
activity andstatus using acoustic recording devices: applications
for island restoration.Journal of Field Ornithology 83: 47–60.
