It is common in the skies over Galapagos waters
to see large, black birds, hovering lazily in place, looking for
all the world like kites. These are frigatebirds. Frigatebirds
belong to the family Fregatidae, which contains five species world-wide.
In the Galapagos there are two species: the great frigatebird
(Fregata minor) and the magnificent frigatebird (Fregata
magnificens). Of the two, the great frigatebird has the greater
world-wide distribution, being found primarily throughout the
tropical Pacific and Indian Oceans, while the magnificent frigatebird
is found in the Caribbean and on the Pacific and Atlantic coasts
of the Americas. The Galapagos population of magnificent frigatebirds
is considered to be an endemic subspecies. In the Galapagos, the
two species can be seen nesting side by side on N.
Seymour, but when frigatebirds are sighted in the air, they
typically are magnificent frigatebirds, because great frigatebirds
tend to forage much farther out at sea. As with the three similar
species of booby, essentially similar species avoid competition
by feeding in different locales.
As members of pelecaniformes, frigatebirds have
the key characteristics of all four toes being connected by the
web, a gular sac, and a furcula that is fused to the breastbone.
Although there is definitely a web on the frigatebird foot, the
webbing is reduced and part of each toe is free. Frigatebirds
produce very little oil and therefore do not land in the ocean.
In 10 years of observing frigatebirds, I have only seen two individuals
in the water and this was accidental: two juveniles crashed into
each other and fell in. With some difficulty they were able to
get out. The gular sac is used as part of a courtship display
and is, perhaps, the most striking frigatebird feature.
Male frigatebirds are black with a patch of red
skin at the throat that is the gular sac. During courtship display,
the male forces air into the sac, causing it to inflate over a
period of 20 minutes into a startling red balloon. As males tend
to display in groups, the effect is magnified. Then the males
sit quietly in the low shrubs watching for a female to fly overhead.
At this, the males waggle their heads from side to side, shake
their wings and call. If the display is attractive enough, then
the female will land and sit beside her amour.
The two species of frigatebird are very similar
to one another, the males being the most difficult to distinguish.
The call is one of two ways to distinguish the males of the two
species from each other. Great frigatebirds make a "gobbling"
sound, not unlike a turkey, while magnificent frigatebirds make
a rattling or drumming sound. A second, more subtle way to distinguish
the nearly identical males is to look at the scapular feathers,
long feathers that cover their shoulders. Although the feathers
are black, they are irridescent and produce different colors when
they refract sunlight. In magnificent frigatebirds the irridescence
is purple while in great frigatebirds it is green. It is easier
to distinguish the females and juveniles. A summary of differences
are:
Key
Features
Fregata
minor
Fregata
magnificens
Male
Call
gobble
rattle
Scapular
Feathers
green irridescence
purple irridescence
Female
Color of Eye Ring
red
blue
Throat
and Breast
white
black throat
& white breast
Juvenile
Face and
Throat
rust-tinged
white
Frigatebirds build nests in low-lying shrubs and
produce a single egg. Both parents take turns feeding for the
first three months but then only by the mother for another eight
months. It takes so long to rear a chick that frigatebirds cannot
breed every year. It is typical to see juveniles as big as their
parents waiting to be fed. When they sit waiting for endless hours
in the hot sun, they assume an energy-efficient posture in which
their head hangs down, and they sit so still that they seem dead.
But when the parent returns, they will wake up, bob their head,
and scream until the parent opens its mouth. The starving juvenile
plunges its head down the parent's throat and feeds at last.
The name "frigatebird" calls to mind
the sails of ships and, indeed, frigatebirds sail gracefully in
the air currents overhead. Their wingspan is some 7.5 feet and
their deeply forked scissor-like tails afford them ultimate maneuverability.
Their other common name, however, the "man-o'-war" bird,
reflects the way in which they use their consumate flying and
maneuvering skill. Frigatebirds are pirates who harass incoming
birds, especially boobies until the victim is so upset that it
disgorges its catch. The frigatebird then drops with amazing speed
and plucks the bolus out of the water, or even catches it before
it hits! Not only do frigatebirds harass other species, but other
frigatebirds as well. The disgorged bolus may pass through several
beaks before it is finally swallowed. In addition to stealing
food from boobies and from one another, they steal nesting materials
as well. It was this kind of piratical maneuvering that caused
the two juveniles to crash into each other and fall into the sea.
Their reputation for piracy, however, may be somewhat
exagerated. With their great maneuvering skill and their long,
strongly hooked beaks, frigatebirds can glide along the surface
of the water, swing their head down, and pluck out fish and squid.
In a similar manner they can pick up hatchling sea turtles, unprotected
chicks, and disgorged food right off the ground. It is also common
to see a frigatebird skimming over the surface of El Junco, a
rare fresh-water lake on San Cristobal, dipping its beak down
and sipping a drink.
It is common in the skies over Galapagos waters
to see large, black birds, hovering lazily in place, looking for
all the world like kites. These are frigatebirds. Frigatebirds
belong to the family Fregatidae, which contains five species world-wide.
In the Galapagos there are two species: the great frigatebird
(Fregata minor) and the magnificent frigatebird (Fregata
magnificens). Of the two, the great frigatebird has the greater
world-wide distribution, being found primarily throughout the
tropical Pacific and Indian Oceans, while the magnificent frigatebird
is found in the Caribbean and on the Pacific and Atlantic coasts
of the Americas. The Galapagos population of magnificent frigatebirds
is considered to be an endemic subspecies. In the Galapagos, the
two species can be seen nesting side by side on 
The name "frigatebird" calls to mind
the sails of ships and, indeed, frigatebirds sail gracefully in
the air currents overhead. Their wingspan is some 7.5 feet and
their deeply forked scissor-like tails afford them ultimate maneuverability.
Their other common name, however, the "man-o'-war" bird,
reflects the way in which they use their consumate flying and
maneuvering skill. Frigatebirds are pirates who harass incoming
birds, especially boobies until the victim is so upset that it
disgorges its catch. The frigatebird then drops with amazing speed
and plucks the bolus out of the water, or even catches it before
it hits! Not only do frigatebirds harass other species, but other
frigatebirds as well. The disgorged bolus may pass through several
beaks before it is finally swallowed. In addition to stealing
food from boobies and from one another, they steal nesting materials
as well. It was this kind of piratical maneuvering that caused
the two juveniles to crash into each other and fall into the sea.