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THE GREAT FRIGATEBIRD (IWA)
The great frigatebird can be seen soaring in the skies over all
the Hawaiian Islands. With its long pointed wings and forked tail,
as well as its light weight (about two and one-half pounds), the
great frigatebird is an extremely graceful flyer. This acrobat
of Hawaii's seabirds can make sharp spiral turns and dive at great
speeds through the air. The great frigatebird's body is about
43 inches long. It has a wingspan of over seven feet. The females
are larger than the males, and are black with white feathers on
the throat and upper breast. The male is entirely black, with
a bare red pouch of skin under the throat. The male blows up this
pouch like a balloon when he is in the colony and wants to get
a female's attention. The pouch is usually not seen when the male
is flying.
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FEEDING
Frigatebirds have oil glands to waterproof their feathers so they
can dive for fish as other seabirds do. They can drift slowly
above the water, using their long hooked bills to snatch up floating
food such as fish, squid, newly hatched sea turtles and flying
fish. Most of the frigatebirds' food is caught using this surface
feeding method. Great frigatebirds are also called man-of-war
birds or iwa (in Hawaiian). These names come from the bird's habit
of bothering other seabirds, chasing and diving at them until
they drop their food. Then with its great speed and agility, the
frigatebird dives to catch the food before it hits the water.
Because there is little webbing between the toes, it is very difficult
for the iwa to kick off from the surface of the ocean. They will
never land in water on purpose. Iwa have trouble standing or walking,
but can glide effortlessly for many hours.
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NESTING
Most of Hawaii's frigatebirds nest on the Northwestern Hawaiian
Islands, although some nest on Kaula Rock (near Niihau) and some
on Mokumanu Island near Oahu. The female great frigatebirds are
biennial breeders: they nest every other year. The males gather
in a colony and attract females, showing off their puffed-up throat
patches. After choosing their mates, the adult iwa collect the
nesting materials. They
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| often steal twigs and branches from other
nests. Flat nests are built in bushes; many eggs fall out of these
crude nests before hatching. The female lays one white egg in March
or April. |
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Both adult birds take turns to incubate,
or sit over the egg. The chick hatches after 55 days. The chick
has no feathers when it hatches and one parent must stay with it
at all times to protect it from the sun's heat. After a month the
chick will be covered with white down (fluffy baby feathers). The
young iwa are fed every 18 hours and stay in the nests for about
145 days After they fledge (grow adult feathers and can fly), they
still rely on their parents for about a year. |
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MIGRATION
Great frigatebirds are migratory seabirds. Each year they travel
from the nesting area to a better feed-ing place, then return
to the nesting grounds. Iwa are more numerous in the main Hawaiian
Islands in the summer months. It is thought that most of them
migrate to the Northwestern Hawaiian Islands in the winter.
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IWA ARE HELPFUL TO MAN
Great frigatebirds seem to warn of an approaching rain storm.
Since they don't want to get wet they will fly away from the storm.
When iwa are seen farther inland than usual, a storm from the
ocean can often be expected. Frigatebirds are important to fishermen.
Boobies, petrels and other seabirds will fly close to the ocean's
surface, feeding on a school of fish. The large black frigatebird,
hovering above and diving at the other birds, can help fishermen
locate schools of fish from afar.
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