More birds out there than previously thought

To: <>, <>
Subject: More birds out there than previously thought
From: "Ricki Coughlan" <>
Date: Fri, 24 Jun 2005 20:14:47 +1000
Hi again
Sorry for appearing to make a sweeping generalisation. Variances from 1- 5khz may occur in some species whilst among Barn Owls it can be up to 20khz - which is way out of the range for humans. Humans may hear very quiet sounds in ranges that some assemblages of birds may not as in the case of Oscine Passerines, which hear higher frequencies better than us but not lower frequencies. Generally, frequency discrimination is only around half as good among birds as humans in some frequencies but this varies considerably from species to species. The upshot of all this is that there are instances where we cannot percieve all of a bird's song.
>I'd be very surprised if variation in syringeal morphology produced song differences perceptible to birds and not humans, and would like to see the data.  Syringeal morphology determines the gross >characters of the song such as fundamental frequency.  Fine temporal structure presumably stems from neural control.
I don't believe that there is any data to support your claim that variances in syringeal morphology don't produce changes to bird song which is impossible for humans to detect. Surely this is highly likely, especially given that there are birds out there producing vocalisations which we cannot completely hear. If these variations arise from fine temporal structure, then this is yet another factor which would be supportive of Watson's thesis. Your point that subtleties in song may be more about conspecific species recognition rather than species recognition is well made and the subject of recent studies. However, conspecific species recognition may very well not be the only reason that we have subtleties - and sometimes imperceptible ones - in avian vocalisation.
>I agree but vocalizations are a diagnosable character and heavily used by birdwatchers so you are not supporting Watson's thesis.
We return to the fact that although often vocalisations may be used as a diagnositic tool at least some parts of a bird's song may not be audible to humans. Thus these vocalisations cannot be tools which are used by bird watchers all the time and this is supportive of Watson's thesis.
>> The numbers of specialists in various areas who will relish the difficulties in diagnosing various hard to split groups of species accounts for a very small number of birdwatchers.
>Perhaps, but these are very people Watson says are hampering bird taxonomy, the "senior ornithologists with extensive experience" on checklist committees
I don't accept that these specialists are necessarily the people who sit on checklist committees. They're often the people who'll scan flocks of gulls for many hours at a time in search of a vagrant. They love to work through flocks of thousands of Red-necked Stints in search of the one Broad-billed Sandpiper among them today (I'm over it after 100). They probably weigh down boats on pelagic expeditions where ID skills are often tested to the max. But sitting on checklist committees: I'm not convinced.
The point that David was making is that avian species diagnosis is made on a very restricted basis, compared to other classes and this is biased toward field diagnosability. This has led to fewer species being recognised than would otherwise be, were we to adopt similar measures employed by those who study other classes of organisms. The conclusion is that there may well be important consequences for ornithology as well as other disciplines which may also use birds to measure patterns of bio-diversity. My personal conclusion (and fear) is also that there may be many species slipping through our fingers into oblivion because we are not applying the appropriate measures when making species diagnosis.
I find the data presented by David to be totally convincing and that there is too much delving into the minutiae in the responses to his article, thus the point is being lost. I also believe that the "senior ornithologists with extensive experience" should look very carefully at David's assertions and, it appears, that I'm in good company, with the likes of Les Christidis and Walter Boles concuring or at least providing thoughts or information which is not antagonistic to David's thesis.
Broome WA

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