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ZooNooz Article - June 2002
Cracking the whip
Helping captive Eastern Whipbirds to sing correctly could be the answer
to boosting their reproductive success.
Photographs Jo Nevin and Taronga Zoo Archives
The whip crack call of the Eastern
Whipbird is a familiar sound in the
dense, moist thickets of coastal
eastern Australia. The call signals
territory and identifies the caller's
position and is made up of two
distinct parts - the "whip", which is
made by the male, and the "crack"
which is the female's reply. It is
thought that the female will only
respond to her mate if his call has
specific characteristics, so the male's
ability to make a call which she will
understand becomes all important to
the success of the mating game.
"The presence of so many other
birds appears to help wild birds learn how to
call correctly, thus ensuring successful
mating and reproduction."
In the wild, this behaviour occurs
naturally. There, a pair of Eastern
Whipbirds is usually surrounded by
many others, some in pairs, others in
search of a mate, as well as juveniles
attempting to establish a territory.
Young chicks are also exposed to the
voices of their parents and siblings
along with birds of surrounding
territories. The presence of so many
other birds appears to help wild birds
learn how to call correctly, thus
ensuring successful mating and
reproduction.
Whipbird |
But in a captive environment the
birds are housed as single pairs with
few or no other neighbours of the same
species, and young are often removed
from their parents just after fledging.
This may make it more difficult for
them to develop their vocal repertoire
and may be the reason why some are
unable to interest the opposite sex in
mating. They often fail to reproduce
or attempt to do so unsuccessfully.
A study at Adelaide Zoo by
former Taronga keeper Tristen Bird
and research scientist Dr Greg
Johnson is attempting to understand
the call characteristics of whipbirds
and how calls are related to
reproductive behaviour. The study
is also looking at whether enriching
the captive birds' environment
by introducing appropriate stimulus
calls might improve their reproductive
success.
Adelaide Zoo has a large
population of captive whipbirds, many
of which produce significant breeding
results every season. However, some
are not successful breeders - many
incubate infertile eggs, while others
build nests but take no further
interest in mating.
The first part of the study plan
was to record, catalogue and analyse
as many voices and calls and as many
behaviours as possible from each bird
in the study group. Using Steinheiser
Cannon unidirectional microphones,
Sony DAT and cassette recorders, and
the Canary Avian Sound Analysis
Program developed by the Cornell
Bioacoustics Institute, it was found
that the call characteristics of
individual birds, and in particular
juveniles, varied in make-up,
complexity and frequency.
The next step in the study was to
observe the birds' responses when
they were played recorded calls of
other Eastern Whipbirds. The calls
were played between 6:30 and 7:30am,
when the birds are usually calling the
most, and included familiar calls of
other birds in the territory and of their
paired mate, as well as calls of
unfamiliar birds.
Whipbird |
When they heard the calls, the
males in the study group became quite
defensive, keeping watch for the
whipbird that had overstepped the
boundary of his established territory.
Spectrograms of the male's defence
call showed it was somewhat different
from the whip crack call used to
signal territory and call position. Both
calls begin with a low whistle, but the
whipcrack produced by the male
when advertising his presence rises in
pitch, while the whipcrack of the male
that is responding defensively to an
intruder falls in pitch.
The wide diversity of calls recorded also suggests that females may have a preference for a certain type of call.
The paired females exhibited
submissive behaviour, silently
retreating to the rear of the exhibit
while the male defended the territory.
The female birds would not respond
to any recorded male or even to the
live call of their own mates while the
males were in this defensive state.
The study results suggest that by
using playback calls to enrich the
whipbirds environment, it is possible
to encourage natural behaviours such
as display, communication and
reproduction.
The wide diversity of calls
recorded also suggests that females
may have a preference for a certain
type of call. It may also be that
juveniles must be a certain age before
they can learn this call. Further
research is under way to confirm
these theories, and to understand why
many juvenile birds do not learn to
successfully reproduce in a captive
environment. As this species has such
superb song-learning capabilities,
future research will also include
imprinting attempts with juvenile birds
to try and teach the perfect song.
Should these techniques prove to
be successful with the Eastern
Whipbird, it is possible they could
be applied to both the natural and
captive environments of the
endangered Western and Mallee
Whipbirds.
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