Small,
stocky, long-tailed black and white shearwater. Tube-nose. Tail appears
longer than other small black and white shearwaters (Manx and Little)
occurring in the North Atlantic. Amount of white in under tail coverts
more variable than what is shown in most field guides. Legs dark
bluish-black. Bill tip to tail length 12 inches (30 cm). Wingspan ~69
cm. Because of their nocturnal behavior around breeding sites they are
unlikely to be detected by casual observation except by voice. Several
recordings are below.
As
adult. Juveniles moult flight feathers the following spring. Downey
chicks are small, grey, downy balls with dark eyes, bills and feet.
Eggs are white.
Systematics
One
of three small black and white shearwaters occurring in thee Atlantic.
The relationship between Audubon’s and the smaller, more temperate
Little Shearwater is not fully resolved. As a result of their rather
sedentary nature and high fidelity to nest sites, limited genetic
exchange exists between populations of Audubon’s Shearwaters. At least
12 subspecies, each with considerable variation in overall size, are
recognized. Nominate subspecies endemic to our region of the western
North Atlantic. P. l.
loyemilleri is smaller and in the breeding season
at least, is confined to western Caribbean. This subspecies is close to
extinction but no recent population assessments are available. Lee
(1988) provides comparative measurements of the black and while
shearwaters of the Atlantic basin.
Likely locations
At
and near breeding sites throughout the region, and in tropical and
sub-tropical seas along oceanic fronts, near areas of upwelling.
Regularly in the Gulf Stream off the Southeastern US in the warmer
months.
Distribution
Nesting
populations are widespread in tropical seas with a few populations
extending into the sub-tropics. In the Atlantic, they breed throughout
the West Indies region and in the Cape Verde Islands; in the Indian
Ocean Audubon’s Shearwaters nest on islands in the Arabian Sea,
Mascarene Is., Aldabra, Seychelles, Amirante, Maldives and Chagos
Islands. In the Pacific they breed on the Galapagos Islands, Bonin and
Volcano Islands, and also Banks and New Hebrides and throughout the
central Pacific.
Nesting
occurs in Bahamas, throughout the West Indies and on various islands in
the Western Caribbean. Disperses to adjacent tropical and subtropical
seas in non-breeding period. Follows Gulf Stream northward and is
commonly encountered off the Carolinas, and regularly north to New
Jersey and New York. Typically in deep waters over Outer Continental
Shelf, with storm driven birds and vagrants occasionally found in other
areas of the Atlantic basin.
There is very little information about the populations of the
subspecies P. l.
loyemilleri that once nested off the Caribbean coast of
Panama.
Biology
At
sea
Highly
pelagic, seldom seen from land. Post breeding birds disperse widely
from nesting areas moving mostly northward as the surface waters of
warm summer tropical seas become less productive. Foraging both diurnal
and nocturnal. Feeds along current edges and similar marine boundaries
and over upwellings. Major food items small fishes (in 94.1%
of
stomachs examined), squid (65.5%), and crustaceans (6.3%). Off North
Carolina, this
species is a Sargassum
specialist; most of the prey items recovered
from stomachs of birds collected at sea represent Sargassum associates.
Feeds on the wing or while swimming. Birds observed in the Gulf Stream
take
only shallow dives, but adults feeding chicks in the Bahamas were found
to dive to maximal depths of 29 m (median=7m; n=131; Mackin, 2004).
Often feed in
large mixed species flocks. Molting adult birds are common from July to
September off NC coast.
At
the nest
Audubon’s
Shearwaters breed in a variety of situations. The only common
denominator to all breeding sites is the absence, or near absence, of
introduced terrestrial predators. Typically nest in natural cavities or
under
rocks, but will also dig their own burrows. The length of the burrow
depends on the nature of the substrate. They also nest in the open
spaces beneath rocks and coral rubble, under Agavi
leaves, rock walls, and other forms of shelter. Nesting may be anywhere
from just above the high tide line to higher elevations in the interior
of islands (e.g. Saba, NWI). Where suitable nesting sites exists these
shearwaters tend to form small colonies. Wind gaps in vegetation can
result in dense sub colonies where conditions for entry to nest
cavities is enhanced.
Females
lay a single egg. Nests are simple depressions in the
substrate. Both birds incubate with each incubation shift lasting
several
days. Breeding activity varies with location. Typically adults appear
at nesting colonies in late winter. Eggs are laid in mid-spring (12
March - 23 May extreme egg dates for Bahamas). Most eggs hatch by
the beginning of June.
Most young and adults disperse from colonies by the beginning of
August. Incubation
lasts about 48 days, and fledging 62-100 days. This protracted breeding
cycle
increases the amount of time they are vulnerable to terrestrial
predators.
Shearwaters
will not fly over land during daylight or moonlit periods of the
night. The best time to search for birds is the two-week
period
around the new moon. Around the new moon, the colony will reach
sufficient darkness for
the greatest number of birds to visit.
Current Population
Audubon's
Shearwaters have been reported at 124 sites with 10 sites that have
more than 26 pairs and 11 sites that have been extirpated including
large islands such as Anegada, Eleuthera, Abaco, Bermuda, Mona, Monito,
and Anguilla. Limestone sinkholes on Mona island are filled with
shearwater subfossils, indicating a formerly huge population. Mona has
become infested with rats, cats, feral pigs, and goats, all of which
negatively affect shearwaters.
Location
Colonies
Low
Estimate
High
Estimate
Antigua
and Barbuda
2
0
10
Anguilla
2
0
10
Bahamas
43
1283
2383
Barbados
3
10
200
Bermuda
1
0
0
British
Virgin Islands
5
2
50
Colombia
1
0
0
Cuba
1
2
2
St.
Martin
1
0
1
Guadeloupe
3
2
30
Grenada
5
7
55
Haiti
1
0
10
Jamaica
1
5
14
Martinique
4
53
121
Navassa
1
1
10
St.
Maarten
1
1
10
Puerto
Rico
15
12
81
Saba
5
15
21
St.
Barts
1
0
10
St.
Eustatius
2
2
20
Tobago
2
200
500
Turks
and Caicos
6
6
60
US
Virgin Islands
5
27
75
Venezuela
13
13
130
Panama
1
1
100??
Total
125
1642
3903
Many
of the colonies of both subspecies have not been visited at night and
are in need of surveys during the breeding season. Sites in the
Cay Sal Bank and out islands of the Bahamas Archipelago (Walker's Cay,
Pelican Cays at Abaco, East and West Plana Cay, Ragged Islands, Long
Cay near East Caicos) and in the Los Roques Archipelago are the most
isolated from humans and the most likely to show larger populations of
this species.
P. l.
lherminieri (Most
of the region)
The
population estimates for this species show a persistent drop in
numbers. Van Halewyn and Norton (1984) estimated about 5,000 pair in
the region. A more detailed assessment fifteen years later indicated
that the
total population was between 3,000 and 5,000 pairs (Lee 2000). We
currently suspect the total population to be 1600-3,800 pairs. While
some of this ‘loss’ is a result of better information on colony sizes,
historical records indicate that this was a much more common and
widespread species in recent times.
P.
l. loyemilleri (Central
American Coast)
Western
Caribbean subspecies believed to be close to extinction (van Halewyn
and Norton 1984), although Olson (pers. comm.) reports:
"We
collected 3 young on one of the Tiger Rocks on 24 April 1990 after no
long search. The islands are covered with dense vegetation that
would inhibit much human exploitation of shearwaters so unless
predators have been introduced in the last 19 years there would be no
reason to consider that the population there is any more imperiled than
at any time in the post-Columbian past. "
Conservation Status
While
in some areas of the world this shearwater appears to be quite common,
the Atlantic population is small and the species has disappeared from a
number of former breeding sites. These include Bermuda, various islands
in the Bahamas, Puerto Rico, Culebra, Mona, Monito, the British Virgin
Islands, the Grenadines, and islands in the Western Caribbean.
Introduced predators, mostly rats and feral house cats are a major
problem and populations on many islands continue to decline. The West
Indies population regarded as near threatened by Schreiber and Lee
(2000).
Conservation Needs
In
the Antilles, the fat young are still prized for food and patrolling of
colonies and pro-active protection of the larger ones is warranted.
Closure of major nesting islands during the breeding season is highly
recommended. In addition to poaching by island residents, there are
additional problems associated with boat refugees from Cuba and Haiti.
Stranded refugees have been documented to devastate Audubon's
Shearwater colonies when they are stranded on remote cays for weeks on
end (Bahamas, Cay Sal Bank 1999; >200 adult shearwaters killed
by
Cuban refugees) and it can be assumed that similar events have gone
undocumented.
Predators,
especially rats and house cats,
are the major problem. Rats and house mice are particularly
troublesome. Not only do
they affect nesting success, but their presence also helps sustain
other predators such as house cats, and native ones like Barn Owls
(Mackin 2008).
David
Wingate (pers comm.) believes that lights disoriented the last
surviving Audubon’s Shearwaters in Bermuda. This seems likely as all
known extant colonies are on remote islands away from any permanent
light source.
It
would be a most worth while project to reintroduce Audubon's
Shearwaters to Bermuda. There are protected island sites that are free
from house cats and Rattus,
and the methodologies for translocating and
inprinting seabird chicks to new sites are well established. Not only
would such a program return an extirpated native species to Bermuda,
but the documentation the methodologies of a successful regional
transplant of this shearwater to a former nesting location would be
useful for creating guide lines for future conservation efforts for
this and other seabirds. Perhaps as importantly it would create a
tremendous opportunity to educate the people of the region about the
plight of seabirds and be a pioneering program for conservation
agencies of two regional governments in addressing issues regarding
formerly shared faunas.
A
systematic inventory of known and suspected nesting sites is needed.
The problem is that these birds are difficult to census and results
from different researchers might provide results that would not be
comparable. Their cavity nesting behavior is only part of the problem,
for most populations we do not have a clear understanding of their
local breeding synchronization. Of specific interest would be surveys
of the islands off the northern coast of Cuba. While there are no
reports from this area it would be surprising if these shearwaters were
not present. With the exception of the endemic West Indian petrels
(Pterodroma),
our knowledge is less complete for this species than any
other of the seabirds of the region. These baseline surveys are
important in that they would provide both a better understanding of the
current population as well as allowing us to measure population changes
in the future as they relate to local management and protection
efforts.
The
extent of regional laws, regulations and enforcement is unclear. Until
recently fat salted chicks were sold openly in local markets, and this
practice may still go on in some places. Local education programs are
needed and enforcement personnel need to be in tune with regional
conservation issues.
Specifically
the Bahamas needs to step up education, monitoring, and patrols of its
larger Audubon’s Shearwater colonies. Local wardens and others
concerned with conservation of marine resources need to be aware of
site locations, nesting seasons, and various aspects of the bird’s
biology in order to better protect the species. Other enforcement
agencies present in the area could also help with patrolling the
nesting islands and cays. A number of islands should be closed to all
unauthorized visitation from January through July.
Issues
at sea are limited and at least at the moment not of major
concern. There is no evidence that this shearwater is part of the
by-catch of pelagic commercial fisheries operations in the Atlantic.
Compared to other Procellariiforms, foraging Audubon’s Shearwaters had
slightly lower amounts of plastic ingestion, but it was still high. In a
study of gizzards in collected specimens, 83.3% of birds had floating
plastics and 16.7% had pieces of styrofoam (studies off North Carolina
over a 14 year period; total sample N= 119).
The potential for
mortality from oil spills is high. Up to 75% of the region's population
summers off Cape Hatteras where a discussion continues about offshore
oil exploration in the very area occupied by the shearwaters. In warmer
months, 68% of the birds foraging off North Carolina are adults.
It
has also been suggested that wing energy farms be placed off the North
Carolina coast. Periodically local and federal agencies are asked for
permission to harvest the pelagic Sargassum
from waters off the SE
coast of the United States. Harvesting could have a tremendous negative
impact on this shearwater as well as other species that are dependent
on these alga mats for foraging.
Harris,
M.P. 1969. Food as a factor controlling breeding of
Puffinus lherminieri.
Ibis 111:139-155,
Lee, D. S.
1988. The Little Shearwater (Puffinus
assimilis) in the Western North Atlantic. American Birds
42(2):213-220.
Lee,
D. S. 2000. Status and Conservation priorities for Audubon’s
Shearwaters in the West Indies. Pages 25-39 In E. A. Schreiber
and D. S.
Lee (eds) Status and Conservation of West Indian Seabirds. Society of
Caribbean Ornithology, Special Publication Number 1.225 pp.
Sprunt,
A. 1984. The status and conservation of seabirds of the Bahama Islands.
Pages 157-168 in
J. P. Croxall, P. G. Evans and R. W. Schreiber (eds).
Status and Conservation of the World’s Seabirds. ICBP Tech. Publ., No.
2. 778 p.
van
Halewyn, R. and R. Norton. 1984.The status and conservation of seabirds
in the Caribbean. Pages
169-222 in
J. P. Croxall, P. G. Evans and R. W.
Schreiber (eds). Status and Conservation of the World’s Seabirds. ICBP
Tech. Publ., No. 2. 778 p.
Trimm,
N.A. 2001. Ecology of Audubon’s Shearwaters (Puffinus lherminieri)
at
San Salvador, Bahamas. MS thesis, Loma Linda University.
Trimm,
N.A. 2004. Behavioral Ecology of Audubon’s Shearwaters at San
Salvador, Bahamas. Diss. Loma Linda University.
Trimm,
N. A., Jr., and W. K. Hayes. 2005. Distribution of nesting Audubon’s
shearwaters (Puffinus
lherminieri) on San Salvador Island, Bahamas. Pages
138-146 in S. D. Buckner and T. A. McGrath (Eds.),
Proceedings of the
10th Symposium on the Natural History of the Bahamas. Gerace Research
Center, San Salvadaor, Bahamas.
Acknowledgements
Storrs Olson, Haven
Wiley, Mary Kay Clark, Rick and Kathy Oliver, Chuck Knapp, David
Wingate, Eric Carey, Nathan Wheeler, Jon Micancin, Ted Uyeno, Tiffany
Kiernan, Burke Cathey, Jason Prichett, Kim and Chris Brand, Matthew
Mckown, Twyla Harrington, Claire Campbell, Zach Ewart, Jessica Goshen,
Predensa Moore, Minna Wiley, John Rothchild, Lou Roth, Renee Birk,
Rachel Gross, Shedd Aquarium, Ray and Evelyn Darville, Blew Bayou,
Larry Dougan, Judy and Tom Barbernitz, Exuma Park Volunteers, Stefan
Payton, Bill Hayes, Tony Trimm, Georgia Ornithological Society, Cooper
Ornithological Society,
UNC Biology Department, Animal Behavior Society, American Museum of
Natural History, and Conservation, Research, and Education
Opportunities.
West
Indian Breeding Seabird Atlas by Will
Mackin and David Lee is licensed
under a Creative
Commons Attribution-Noncommercial-No Derivative Works 3.0 United States
License.Based on
work at www.wicbirds.net.Permissions
beyond the scope of this license may be available at www.wicbirds.net.
Suggested
Citation: Lee, D. S., W. A. Mackin. 2009. Audubon's Shearwater. West Indian
Breeding Seabird Atlas
<http://www.wicbirds.net/aush.html>. Last Updated: _____.
Date accessed: ______.
