More birds out there than previously thought

[Michael Todd <>]

Hello all,

I also found David's paper interesting. However, many of Andrew's points 
are well made.
External appearance is certainly a major means of diagnosis of species 
in birds- obviously because birds are often so colourfully and 
distinctly plumaged. Mammals, particularly small ones, are usually 
variations of brown and grey with often great amounts of variation 
between individuals. In mammals, external appearance is often a poor 
means of separating species with a fair amount of overlap as opposed to 
the often clear differences in birds, ie an eyebrow being black or 
white! (as opposed to usually greyish-brown in contrast to usually 
brownish-grey!). I suspect that if external appearance could be used 
more often with other classes of animal it would be.
Nevertheless, I think that David's opinion that possibly good species 
are getting overlooked is worth considering. The level of variation 
between populations of birds is rarely adequately measured. Those who 
record bird calls (such as the Wildlife Audio Sound Recording Group) are 
acutely aware of how much variation occurs within separated populations 
of common species. This is putting aside the issue of whether or not the 
calls are audible to us or not.  Could any of these different calling 
populations be hidden separate species? Well possibly...
Works such as the monumental Directory of Australian Birds (Vol 1) have 
attempted to describe the variation at a finer level using ultrataxa. 
This was mostly based on external appearance (skins) and internal 
morphology (bones) but used other info if it was available. Many 
Australian birds haven't had their genetic variation determined between 
what we now call species let alone between different populations. 
Analysis of behavioural differences between populations hasn't been done.
I guess what I'm trying to say is that we know very little about most of 
our birds and I don't know that it is so much a bias away from methods 
other than external appearance. It's more that we don't have much of the 
other info- you use what you have don't you?
Cheers

Mick

Michael Todd 
Wildlifing 
Images & Sounds of Nature
Latest Additions: The Awaba Forest
www.wildlifing.com
Toronto, NSW, Australia 
04101 23715


Andrew Taylor wrote:

> On Fri, Jun 24, 2005 at 08:14:47PM +1000, Ricki Coughlan wrote:
>  
>
> >   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.
> >    
> I don't want to be tiresome but this is a topic I know well and this
> isn't true.  Barn Owls have the best high frequency hearing of any bird
> tested but their high frequency limit is 12khz.  See Dooling's chapter
> on auditory perception in Volume 1 of Acoustic Communication in Birds
> or look at the audiograms in the appendix of
> http://www.nrel.gov/docs/fy02osti/30844.pdf
>
> Presbycusis is taking its toll but judging by the audio generator on my
> workbench my ears still get close to the  20khz limit usually nomimated
> for humans.  We can hear high frequency sounds better than any known bird.
>
>  
>
> >  in the case of Oscine Passerines, which hear higher frequencies better
> >   than us but not lower frequencies.
> >    
> Again this isn't true. Look at the audiograms in the above ref.
> The oscine passerines' hearing sensitivity peaks are at 1.5-4khz.
> Around these peaks their sensitivity approaches and in some cases exceeds
> human sensitivity but at higher frequencies their sensitivity is much
> poorer than humans.  
>
>  
>
> >   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.
> >    
> True - its just speculation based on naive physics.  But Watson's argument
> that syringeal morphology would be useful in separating crypto-species
> is also purely speculation.
>
>  
>
> >   especially given that there are birds out there producing
> >   vocalisations which we cannot completely hear.
> >    
> Its possible their are crypto-species with calls with diagnostic temporal
> features that can not be distinguished by humans but without examples
> this is pure speculation.
>
>  
>
> >   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 isn't true.  Look at Figure 1 of Watson's paper.  Reptile
> descriptions have a more restricted basis than birds, frogs and birds
> are similar, only mammals have species definitions which are clearly
> more broadly based than birds, at least using these categories.
>
> Bird descriptions may rely more heavily on characters observable in the
> field but the causes and consequences are the issue.
>
> Andrew
>
>
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