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Geographic
range: Worldwide in tropical seas. In Mexico breeds on islands
off Baja California and in Gulf of California, from where its range
spreads south along Pacific Coast. This species is less frequent in
the Gulf of Mexico, breeding probably on islands off Campeche, Yucatan,
Quintana Roo and Belize.
Physical
characteristics: S. leucogaster
is a large seabird reaching 71-76cm (28-30 in) with a wingspan of
137-145 cm (54-57 in) . Adult has dark brown head, upper parts, and
breast, with sharply contrasting white belly and white underwing coverts.
Immature is gray-brown above and below; darker on head, wings, and
tail.
Maximum known age was 16 years.
Food
habits: Feeds by plunging head first into the water from the
air. Usually forages near shore, often within 80 km of breeding grounds.
Usually a solitary feeder. Primary prey item is flying fish. Feeding
generally occurs during daylight hours.
Reproduction:
Breeding season occurs between March and November. This species
breeds colonially. Nests are located on the ground and consist of
a shallow depression surrounded by twigs or other vegetation. An average
of two chalky white eggs are laid Lacks brood patch and instead incubates
with feet. Parents share incubation duties. Average incubation shift
is 12 hours. Incubation period averages 43 days. Siblicide exhibited
by chicks. The first egg hatches several days before the second. The
first chick to hatch ejects the second chick from the nest shortly
after it emerges from the egg. Chick feeding occurs on average once
every 17 hours. Fledging occurs 85-103 days after hatching. Post-fledging
care and feeding continues for one to two months.
Behavior:
Usually silent bird, but gives a variety of quacking, grunting,
and screeching calls on the breeding grounds.Of the boobies seen off
the beaches of the Gulf of Mexico, this species is by far the most
plentiful. Like the Northern Gannet, they dive for fish by plunging
into the sea, but they also skim the surface to catch flying fish
that leap clear of the surf. Frigatebirds often harass boobies, chasing
them and forcing them to disgorge their prey, which the agile frigatebird
then catches in midair. When on the wing, but not fishing, boobies
often flap and glide in lines close to the surface of the waves and
may resemble shearwaters. On land, these birds are dependent on a
strong wind for takeoff from a tree or other elevated perch. On calm
days they rest in vegetation or on the ground.
Habitat:
Tropical and subtropical seas; breeds on coastal islands. |
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