Bowerbirds
· FAMILY: Ptilonorhynchidae
· ORDER: Passeriformes
There are between 20 and 30
species of bowerbird, with members of the family being found in New Guinea and
Australia.
Bowerbirds are famous for
their courtship ritual. This involves the male bird building a highly elaborate
structure – called a bower – to impress the female.
The female is highly
selective, and will only choose a male whose bower comes up to scratch. Once
mating is complete, the male plays no part in nest construction or the rearing
of the young. (The bower is not used as a nest.)
ABOUT
Extraordinary engineers. Some
birds have stunning plumage, some birds have complicated mating dances, but
bowerbirds are creative engineers! To attract females, the males build,
decorate, and maintain elaborate structures—the avian equivalent of bachelor
pads—called bowers. These take many forms, but all are constructed with
gathered twigs and objects like brightly colored stones, fresh flowers, or
iridescent insect skeletons that are specially placed for the most impressive
display.
Although the regent bowerbird
male is bright yellow and black, the female is a drab gray or dirty white in
color.
Bright as crayons. There are 20 different
bowerbird species, and their plumage patterns vary dramatically. They show
a wide variety of colors from green, orange, red, yellow, black, and white to
olive-brown or sooty gray. Some have a brilliant crest of elongated feathers or
even a ruff hanging over the back. Typically, bowerbird females are less
flamboyantly feathered than the males.
Bowerbirds are most
numerous on the island of New Guinea in the South Pacific, but they are
also found in specific areas of Australia. They occupy a range of different
habitats, including tropical forests, mangroves, eucalyptus stands, and savanna
woodlands.
Chatterboxes. Bowerbirds
have a wide range of vocalizations. Some utter loud, harsh notes or hiss,
cackle, and chatter. The calls include mimicry of other birds species’ calls,
sounds from their environment, and sometimes human-made noises. Both male and
female can mimic the sound of predatory birds. The male performs
these calls at the bower, whereas the female vocalizes at the nest if she is
threatened or disturbed.
LIFE SPAN
6 to 30 years, depending upon the species
YOUNG
Incubation: 17 to 27 days, depending upon the species
Eggs: 1 to 3 per clutch
SIZE
Largest: Archbold's bowerbird is 15 inches (37 centimeters) long
Heaviest: Satin bowerbird weighs 5.9 to 10.2 ounces (170 to 290
grams)
Smallest: Streaked bowerbird and yellow-fronted bowerbird at 9
inches (24 centimeters) long
Lightest: Golden bowerbird is 2.1 to 3.3 ounces (62 to 96 grams)
FUN FACTS
Female bowerbirds are attracted to bowers with lots of fruit,
but when the fruit shrivels, the male discards it nearby, in effect planting
more fruit-bearing plants, the first instance of a non-human species
propagating plants for use other than food.
The dullest-colored bowerbird males build the most elaborate
bowers. The drab Vogelkop gardener bowerbird builds one of the largest and most
elaborately decorated of all bowers: a hutlike structure, 5 feet high and over
6 feet in diameter.
Anting, which involves the use of live ants to anoint feathers,
is rarely observed with wild birds, but tooth-billed, golden, and satin
bowerbirds have been recorded doing this.
Nineteenth-century European naturalists thought bowers were
constructed by humans rather than bowerbirds.
Some male bowerbirds have been known to build 9-foot-tall (2.7
meters) teepeelike structures as their bower.
The Perth Mint of Australia has created a series of five silver
coins in its Birds of Australia series. The regent bowerbird is one of the
birds selected.
HABITAT AND DIET
A female satin bowerbird holds
a tasty grub in her beak.
All bowerbirds are frugivores, living mainly on the fruits
of trees and bushes; occasionally, they eat insects, spiders, and seeds. Since
tree fruits are abundant most of the year, and it is a high energy food
source, a fruit diet gives the male plenty of time to build his
bower.
At the San Diego Zoo, the
bowerbirds are fed an assortment of fruit and low-iron pellets. Living in a
mixed-species aviary means they also have access to a variety of choices
offered to their exhibit mates.
FAMILY LIFE
Bower power. Male bowerbirds
are famous for creating complicated bowers that are used for display during the
mating ritual. These bowers can take many forms, with each type of bower
particular to the species but also special to the individual male and his available
resources.
There are three main types of
bower architecture: a cleared area containing an “avenue” or domed tunnel of
sticks, just wide enough for a bowerbird to pass through and sometimes painted
with vegetable juices; a “display court” with large leaves laid upside down or
tiled with rocks; and a “maypole,” which uses a sapling as a central tower,
with an assortment of vegetation packed around the base, with or without a
roof, sometimes many feet tall.
A male may spend a week to two
months getting his bower in order, depending on whether he is refurbishing a
previously used structure or building a new one. Some bowers built by male
satin bowerbirds have been maintained for more than 30 years, and both males
and females of this species are known to live 20 to 30 years.
Avian artists. Once the
bower is complete, the male adds decorative touches using everything and
anything he can find and carry: seeds, pebbles, snail shells, berries, ferns,
lichens, dead beetles, fresh flowers, spider webbing, bones, leaves, even bits
of glass, cloth, plastic, aluminum foil, and other items discarded by
humans.
Different species favor different
colors. For example, the striped gardener bowerbird prefers yellow, red, and blue
objects. The fawn-breasted bowerbird favors green. Males of some species also
“paint” their walls with a mixture of charcoal dust and saliva or plant juices.
The bird uses his beak or a bit of chewed bark as a paintbrush.
The male continuously defends his
bower, rearranging baubles he has used to decorate the area, collecting
fresh replacements, dabbing a little touch-up paint on the walls, and hovering
over his masterpiece. When not inside his bower, the male may perch a few feet
above it and watch for an eligible female or an intruding male that may try to
destroy his bower. If a female is enticed by the architecture, she will visit
the male, be entertained by a song or dance on his stage or court, and decide
if he is worthy.
Bowers are not nests. After
the male dances, sings, and grovels along the ground, seemingly begging a
female to accept him, they mate, and the female usually leaves. If she lingers,
the male may drive her out so he can tidy up his bower and prepare for the next
song-and-dance routine used to attract yet another mate.
After mating, the female builds
a cup-shaped nest in a higher, more secluded location in a bush or a
tree hole. She builds the nest alone, also being solely responsible for laying
eggs, incubating, and feeding the young. Laying a clutch of 1 to 3 eggs,
depending on the species, she incubates them for 12 to 15 days. The eggs are
strikingly marked by scribbly lines of brown, gray, purple, and black, as if an
artist had dribbled ink on them. These patterns probably help to camouflage the
eggs.
From hatch to fledge takes about
three weeks, and most mother bowerbirds carry out all the nesting duties solo.
The mother has no difficulty feeding herself and her offspring, possibly caring
for them for two to three months before the young go off on their own. The
white-eared, black-eared, and green catbird species are different: the male
helps feed the chicks.
AT THE ZOO
The San Diego Zoo’s first
bowerbirds, a pair of satin bowerbirds, arrived from the Taronga Zoo in
Australia in 1927. Since then, we’ve also had regent, spotted, and great gray
bowerbirds in our collection. We currently have fawn-breasted bowerbirds in
our Owens Aviary and Parker Aviary. Each male strips off fern leaves
and uses the sticks to build his avenue-style bower.
Fawn-breasted bowerbirds are also
in the Zoo’s new Australian Outback exhibit, where you will find them
in the aviary closest to the Marsupial Wall. There are no ferns in
that aviary, so keepers collect the fern stalks from other areas of the Zoo and
place them in the aviary for the bower builder’s use.
CONSERVATION
There are challenges to
bowerbirds in the wild, though their numbers are mostly stable. Potential
reasons for their decline include predation by feral cats or red
foxes, fragmentation and degradation of habitat by agriculture or grazing, and
potential illegal shooting or poisoning, since occasionally they are seen as
pests. Legislation currently protects bowerbirds and their habitats, while
research, public awareness, and monitoring continue to ensure their stability.