Ian,
Do Rufous Scrubbirds have a suite of mimicked species in the same way
that lyrebirds do? Or is their mimicry more random?
Vicki
On 12/11/2011, at 12:25 AM, Ian Martin wrote:
> Hi Vicki
>
> Yes the recordings are stereo (a twin omnidirectional mic "Soundmeter"
> see http://www.wildlifeacoustics.com/), and so even though we have not
> yet done it, phase differences should tell us the direction of the
> calls
> (well down to two possible directions with just two mics I think). The
> software by the same manufacturer called "Song Scope" IIRC allows
> such a
> phase difference determination.
>
> The software also allows sonogram "recognisers" to be set up to
> identify
> particular calls. Its main use is scan many hours or days of
> recordings
> for those "recognised" calls and to log them in an excel type
> database.
> Compared with a human ear and brain combination however, it only has
> about 80% to 90% success rate. This rate is determine for each
> recording
> by listening to say 15 mins of "typical" sample and running the
> software
> over the same part. From that sample the relative detection success
> rate
> for the software vs human ear can be determined for that recording and
> then the software result from scanning the days of recordings is
> scaled
> up by that factor - beats listening to days and days of recordings in
> real time and you always have to log to help you to zero in on likely
> interesting bits and listen to them anyway.
>
> But for possible mimicked calls it isn't able to distinguish the real
> call from the mimicked ones - understandable when we have trouble with
> it too. And of course the recordings are not that good either despite
> high sampling rates and deep bit depth ... mainly because the mics
> have
> to be omnidirectional to pick up bird cals from any direction. This
> means of course that they also pick up sounds from insects (especially
> crickets and cicadas !!!), leaves rustling in the wind, rain drops
> falling through the leaves (it's a rainforest and so plenty of rain),
> overhead aircraft, passing bushwalkers talking, distant motor
> vehicles,
> etc, etc. And so as recordings of bird calls they leave a lot to be
> desired. But it's still a really good way to be able to get lots of
> data
> without having to actually stay there for days or weeks and the birds
> are undisturbed and call more freely as well.
>
>
>>
>> Stereo recordings could be useful for unmanned surveys of Rufous
>> Scrubbirds, i.e. so that you could tell the direction of the calls.
>>
>>
>> Vicki Powys
>> NSW
>>
>>
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