I would appreciate any critical comments on the field
notes below regarding the vocal behaviour of the Eastern
Whipbird. Although my interpretations presented below
are based on minimal information, I do believe there
something going on which contradicts traditional
wisdom.
Feel free to post all comments as public to the list
to encourage an open debate.
Date: August 12, 1998
Place: Lamington NP, Binna Burra
Species: Eastern Whipbird
Throughout the forest, whipbirds were heard emitting a
thin, piercing whistle followed by an explosive "crack of
the whip"; in most cases, singing birds were answered,
presumably by a female (see below), with two to three
descending whistles typically described as "chow chow".
In most instances, the whistle component of songs sung
by whipbirds at a particular locality varied in pitch across
birds, a fact which fits with reports that the "whistle"
provides information of the singer's identification.
However, the whistle of one bird I encountered is best
described as a fast warble, and the whistle component of
two whipbirds who were alternately singing within 6
metres of each other, sounded identical to my ears (I
have musical training). I interpreted the interaction of the
two whipbirds as a one-on-one vocal duel as far as I
could tell a third bird answered their respective calls with
a "chow chow." Were the two birds "intentionally"
matching the pitch of their whistles? In some songbirds,
males involved in territorial disputes will "match" their
opponent's song as a way to direct their aggression at a
specific target; in other species, the reverse strategy is used
by switching to a new song.
Whipbirds can vary the pitch of their whistles. Do they
match their whistles during confrontation? In an attempt
to find out, I recorded the calls of several whipbirds at
different locations. I then played these recordings to 6
singing birds. During this simple test, I slowed the speed
of the tape to lower the pitch of the call. Two of the birds
lowered the pitch of their whistles when answering my
playback, suggesting that birds will attempt to match
the call of nearby competition.
Additional Observations at Mt. Coot-tha Park, Brisbane,
on September 8:
At 7:00am, I came across a pair of whipbirds in clear view:
one individual was scruffy looking with tattered feathers
(bird 1) while the second bird looked freshly moulted with
a brilliant white cheek patch (bird 2). I followed the birds
for over 45 minutes while testing their reaction to my
whistled rendition of the long, pure tone component of their call
-- I can not duplicate the "whip-crack". What I observed is quite
revealing.
First, bird 1 exclusively produced the song typical of the
species consisting of a long whistle followed by a whip-crack,
but often it sang only the whistle. Second, bird 2
followed bird 1, and frequently answered bird 1's calls
with a "chow chow". Third, both birds answered my
whistle when and only when, I included a series of short
notes before the long note. And lastly, when I raised the
pitch of my whistle, bird 1 answered but did not match the
"new" pitch. However, when I lowered the pitch of my
whistle, bird 1 instantly lowered its whistle to precisely to
match the pitch of mine, and thereafter sang the low
whistle without prompting.
The level of interaction between the birds suggests that
both were adults, and bird 2, presumably the male, was in
pursuit of bird 1. If so, this would indicate that the female
of the species whistles and "cracks the whip."
Furthermore, the whistle component of the call is what
identifies the singer and is sufficient to evoke a response
from its partner. I propose that the "whip crack" is
directed to outside listeners of the same sex (in this case
presumably female). And lastly, the pitch of the whistle
component can be lowered to match the song of an
intruder; a lowered pitch could be more difficult to
produce and, as a consequence, be preceived as more
threatening than high pitch whistles.
Cheers to all, Jim
Dr. Wm. James Davis, Editor
Interpretive Birding Bulletin
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