Largest
(32-36 inches, 81-92 cm, total length) of the tropical boobies. Can
live to 30
years or more. Female’s mass greater than male’s.
Adults
White with black
in
tail, primaries and scapulars. Adults superficially resemble Northern
Gannets,
but adult Gannets have yellow-hue on back of head and neck. Black tips
of long scapulars make the black wing stripe extend evenly from
primaries to base of the wing. Gannets lack the black tips on
scapulars, making the wingstripe lose width as it nears the body.
White-phased Red-footed Boobies are much smaller and have a distinctive
smudge of black feathers on the wrist in the underwing and lack the
black scapulars on the upper wing.
Juveniles
Immature
and
juvenile Masked boobies have white under-parts, and a white collar.
Juveniles are brown and resemble Brown Boobies, but the brown
is on the head and
neck and does not extend onto the breast as in Brown Booby. Underwing
pattern has a thin brown stripe from 'armpit' to 'hand' bordered in
white both anteriorly and poseriorly. Juvenile Brown Booby has brown
borders to the underwing with a short, thin stripe from the 'hand' that
fades out before it reaches the body.
Alternative names:
English:
White Booby, Blue-faced Booby
French: Fou Masque
Spanish: Piquero enmascarado.
Systematics
Nine
species in
genus Sula including 3 gannets and 6 boobies. Gannets are temperate
to boreal; the boobies are primarily tropical. Four to
seven subspecies of Masked Booby are recognized depending on the
authority.
Differences based on overall size and coloration of soft parts. Western
Atlantic subspecies is endemic to West Indies and Gulf of Mexico and is the
smallest of the named races. Has a straw colored bill and orange to
olive colored legs and feet.
Likely locations
At
and near breeding sites, because of rarity and wide marine dispersal
seldom encountered at sea.
Distribution
Rare,
pan-tropical species; various subspecies occur throughout the world.
While this is the least common species of booby, it is one most
encountered at sea as they disperse great distances from their breeding
grounds. Occurs northward in the Gulf Stream to the Carolinas, where it
is a deep water, pelagic species usually associated with Sargassum.
Biology
At
sea
Plunge
diver,
diving from heights of up to 30 m. Mostly diurnal but some feeding
occurs at night. Feed on flying fish, jacks and squid. Known to forage
65 km from breeding colonies, and dispersing further from nesting sites
than other boobies. Spends considerably portion of the day resting of
surface or perched on floating debris.
At
the nest
Nest on
remote
islands lacking mammalian predators, often in association with other
species of boobies. Colonies are typically on flat unforested islands.
Nest on the ground but do not construct actual nests. Eggs blue but
covered with white chalky layer. Like other boobies they often lay more
than one egg (typically two) but only one chick is raised. Incubation
38-49 days, fledge at 109-151 days but young return to nesting area to
be fed by parents until 139-180 days of age.
Current Population
A
total of 580-650
pairs in 26 known colonies in West Indies. At least five colonies in
the
region have been extirpated in the historic period, and, based in
pre-Columbian middens, several others were lost prior to European
contact.
The vast majority of the Masked Boobies in this population nest outside
the Caribbean, with 3863 pairs on islands of the Campeche Bank in the
Gulf of Mexico.
Location
Colonies
Low
Estimate
Bahamas
1
0
Florida Keys
1
5
Cayman
Islands
1
0
Jamaica
2
114
Puerto
Rico
3
105
US
Virgin Islands
2
80
Anguilla
2
62
Antigua
and Barbuda
1
0
St.
Vincent and the Grenadines
1
0
Grenada
1
1
Trinidad
and Tobago
1
4
Venezuela
7
213
Colombia
2
0
Honduras
1
0?
Mexico (Numbers from 1986)
4
3863
Total
31
4384
Conservation
Status
This
is the
least common booby and one of the rarest birds in the Atlantic. In
the West Indies proper, one-fifth of the breeding pairs use a single
island off Jamaica that they share with several hundred fishermen. The
southern Caribbean population is vulnerable to
a number of factors. Rarely recolonize once populations are extirpated.
Considered endangered in region (Schreiber and Lee 2000; Bradely and
Norton, 2009). Status of the huge Campeche Bank population has not been confirmed since the 1980's.
Conservation Needs
Can coexist
with
carefully regulated ecotourism but is not established on islands near
any tourist centers. Pacific populations have been
rapidly exterminated by feral pigs and have shown dramatic recoveries
when pigs are removed. Feeding behavior at sea suggest
this would be a prime candidate for pelagic fishery by-catch. Rarity of
the species and confusion with gannets probably results lack of
reporting of this booby as a by-catch species.
The
larger more important colonies need monitoring and protection, and
should be off limits to random visits by boaters, tourists and sea bird
biologists. Agencies granting permits for research on cays supporting
booby colonies need to check the credentials and experience of the
applicants.
A
region-wide survey of all historic nesting sites is needed during the
breeding season. These sites should also be monitored for introduced
mammals. Local education, informative posted signs, and enforcement
needed for all known colonies. Active colonies need to be
checked 3-4
times a year to determine breeding success at specific sites and to
identify problems. Because boobies are long lived the presence of a
number of adult birds in a colony does not necessarily indicate
successful breeding. Banding studies to document the amount of movement
and exchange of birds between colonies is needed. DNA analysis would be
useful to compare populations within the West Indies to those nesting
along the Central American and South American coasts.
Photos
Selected References:
Anderson,
D. A.
1993. Masked Booby (Sula
dactylatra). In
The Birds of North America.
No. 73 (A. Poole and F. Gill, Eds.). Philadelphia: The Academy of
Natural Sciences; Waashington, D.C.: The American Ornithologists’
Union.
Clapp,
R. B. and W. B. Robertson, Jr. 1986. Nesting of the Masked Booby (Sula
dactylatra, new record) on the Dry Tortugas, Florida: The
first record
for the contiguous USA. Colonial Waterbirds 9:113-116.
Schreiber,
E. A. 2000. Status of Red-footed, Brown and Masked Boobies in the West
Indies Pages 46-57 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.
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. Masked Booby. West Indian
Breeding Seabird Atlas
<http://www.wicbirds.net/mabo.html>. Last Updated: _____.
Date accessed: ______.
