Syd Curtis made a posting 28 Feb discussing Lyrebird mimicry. I would like
to add further comment to some of Syd's comments ? beware, long message!.
In replying to a query by Tony Russell concerning where the bulk of lyrebird
mimicry takes place, Syd replied "...it is possible some vocalisation was
made away from the display mounds [in Robinson's study], but it would have
been a very minor amount. Lyrebirds,both species, occasionally display on a
rock or log, and that song too would be mainly mimicry, but it doesn't
happen often". In my observations of Superb Lyrebirds I have observed on
several occasions that they give mimicry from sites other than the display
mound, and whilst not engaged in visual display. These observations have
been made both within and outside of the breeding season, and suggest to me
that mimicry away from the display mound constitutes more than a minor
amount of the total mimicry given. For example last July I was at Royal
National Park and observed a male singing on his display mound with mimicry
and species-specific vocalisations associated with display, but also watched
him singing with mimicry and territorial song as he perched in a tree
(including between bouts of preening - the mimicry included the
vocalisations of at least 11 model species), this male also sang with
mimicry as it was moving along the ground. It is interesting to note that it
repeatedly went to sing from the same perch. In fact the bulk of mimicry
that I heard from this male was given whilst away from the display mound
(however, it is only one observation!). Other sightings include observing
male Superbs mimicking while foraging (e.g. April 2000) and while perched ~5
metres above the ground (afternoon, June 1998). The majority of times I have
heard mimicry I haven't seen the bird of course!! Obviously, this may be
very different to what is observed with Albert's Lyrebird, with which I
believe Syd has the most experience with.
My second point relates to the origin of mimicked sounds. Syd states that
"Lyrebirds (both species) learn their mimicry by copying older lyrebirds,
not by copying the other species directly, though occasionally new sounds
may be added to the local repertoire". This idea has been reiterated by many
people and it seems that only with Albert's Lyrebird is there conclusive
evidence that individuals copy one another's mimicry (it is known that this
occurs in Superb Lyrebirds through circumstantial evidence, e.g. mimicry of
species no longer found in the area, lack of mimicry of newly-arrived
species, but the extent to which it occurs remains unknown). Therefore,
before the above statement can be applied to Superb Lyrebirds the relative
importance of conspecific vs heterospecific mimicry needs to be examined as
Syd suggests (with Albert's Lyrebird, sharing of mimicked sounds has been
clearly demonstrated, and it appears that conspecific mimicry is of greater
importance, so Syd's statement may aptly describe mimicry in this species -
see comments below about caution using analogies from other species).
Robinson and Curtis (1996; Emu 96: 258-275) state that the Satin Bowerbird
'territorial' song is a prominent feature of the sequential song of Albert's
Lyrebirds and to quote the authors "....at Lamington and Tambourine the
local bowerbird dialect was accurately reproduced. Comparison elsewhere was
not made but accurate local copying would be expected". I would be grateful
if Syd could answer: why would local copying be expected if males are just
copying from one another's sequential song? (i.e. what was the basis of this
statement?).
If I may speculate a little (or propose an hypothesis for testing) it may be
that individual males favour mimicking one another (i.e. have a preference
for conspecific vs heterospecific mimicry), but also mimic other model
species but may only occasionally continue to produce the mimicked sound
(and incorporate it into their repertoire, whereas they regularly 'store'
mimicry of other male lyrebirds and repeat it - at least with Albert's
Lyrebird!), thus changing their repertoire slightly by adding a new sound,
which may subsequently be copied into the repertoire of other males, and in
this way the song of the species can change over time incorporating new
sounds from the present but also retaining sounds from the past (thus
explaining how the sounds produced by other species are a major component of
lyrebird song). To illustrate: Superbs introduced to Tasmania (1930-40's)
continued to include mimicry of Eastern Whipbirds and Pilotbirds in their
song (up to at least the 1980's after which it apparently was barely
detectable, 1940-1980 is a period greater than the lifespan of a singing
adult male i.e. this provides evidence for ?cultural transmission? of
mimicry) but have since been noted to mimic several Tasmanian endemics
(however, I do not know if this mimicry has been detected during the
breeding season or outside of it) illustrating that birds do indeed
incorporate mimicked sounds from their environment into their repertoire as
well as copying directly from other males.
Lastly, Syd states:
"With Superbs, the mimicry appears to be in random order, but I'm confident
that if anyone took the trouble to tape-record and analyse the mimicry from
all the individuals in one area, it would be found that they all use the
same suite of mimicked sounds".
Presumably this statement stems from the knowledge of song sharing
(including mimicry) in Albert's Lyrebird (which have far less diversity
within an individual in their mimicked sounds than do Superbs). However, I
caution using what is known of Albert's Lyrebirds to draw analogies with
Superbs. The reason being that congeneric species may have rather different
singing strategies, and making assumptions for one species based on what is
known for another may lead to a false understanding. To illustrate the point
take the lyrebird's sister family the scrub-birds: one species has a singing
strategy where the variety in the repertoire of advertisement song is
apparent with a relatively small number of songs given within a bout of
singing (termed immediate variety), while the other has a singing strategy
of eventual variety where songs within a bout are of the same type and one
has to listen to several bouts (and consequently many songs) to realise the
variety in the repertoire. Secondly, the complexity in the songs of one
species is far in excess of that of the other, and the former species also
mimics extremely rarely (if at all!) while the second apparently mimics
frequently. So it can be seen that with these two closely-related species
the singing strategies are very different, which may also occur with the two
lyrebird species. In fact we are already aware of appreciable differences in
the singing behaviour of the two lyrebirds such as mimicry being in the form
of a strict stereotyped song in the Albert's and being less varied, and
mimicry being much more random (supposedly) and diverse in the Superb.
I would welcome any comments that people have about what they have observed
with Superbs in terms of mimicry.
Cheers, Dean
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