An addition to Vicki Powys' posting on this topic.
Vicki wrote:
>
> In reply to earlier postings, Dean Portelli wrote at length on bird dialects
> - an interesting topic. As Dean points out, there is much we don't know
> about dialects - e.g. do birds 'change their tune' at will, are they
> influenced by their new neighbours, etc.
>
> Some years ago I studied the territorial song dialects of Superb Lyrebirds
> in my local area. Lyrebirds are weak fliers and do not travel long
> distances, so were an ideal species for a study on vocalizations. In
> certain rugged terrain the lyrebirds do tend to aggregate into distinct
> populations and the males will all share the same dialect of territorial
> song. Each population also seems to share the same suite of mimicked
> sounds.
>
> I was able to show that geographically and acoustically isolated populations
> of Superb Lyrebirds had very distinctive dialects, and that those dialects
> did not change over a period of many years, and that all the males in any
> one group used the same dialect.
>
> What I was unable to establish was whether or not any lyrebirds moved away
> from their original birth-territory, to new areas. And if they did move on,
> did they then adopt the territorial songs of the population they had moved
> into?
>
> My guess is that, perhaps driven by fire, land-clearing, or the biological
> imperitive to widen the gene pool, some birds would indeed move away from
> their original home territory and take up the songs of another area.
>
(Snip)
In a paper titled "The Vocal Displays of the Lyrebirds" (Emu 96, 258-275)
Norman Robinson quoted Vicki's paper which described the lyrebird dialects
she has referred to, and he wrote concerning Superb Lyrebirds' use of
territorial songs:
"Microgeographic variation occurred in dry sclerophyll forest where
suitable habitat was in acoustically isolated river or creek gorges on the
western side of the dividing range. In Sundown national Park, the Blue
Gorge and the Red Rock Gorge are only 5km apart, but the songs were
distinct. In nearby Black Jack Creek, two males used the Blue Gorge song
but added the the Red Rock Song to it when confronting one another. (D.
Behrens pers. comm.)"
That tends to confirm Vicki's view that an emigrating lyrebird would take up
the songs of the population he joined.
That's my guess too. If a male lyrebird (either species) did move from his
home area and reached another population of lyrebirds it seems likely that
communicating with them would be more effective if he adopted the local
dialect of territorial song than if he stuck to his own. And there surely
can be no doubt that he could accurately copy the local song if he wished.
Their use of mimicry may be a different matter however. With Albert's there
can be no doubt that all the males in any one locality use the same mimicry.
And Vicki has said this applies to Superbs. But maybe some new mimicry
might be just the thing to impress the girls. If so, the newcomer might
retain his own mimicry and add to it any mimicry of the locals that is new
to him.
But lyrebirds are very intelligent. If that happened it is likely that the
locals would soon respond by adding his mimicry to theirs. This is one
possible way in which down the generations, lyrebirds have evolved such
elaborate vocal behaviour.
Syd Curtis
Birding-Aus is on the Web at
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