Re: Great in the air, not so good underwater

[evelyn sobielski <koreke77@yahoo.de>]

--- Michael Habib <mhabib5@jhmi.edu> schrieb:

> > Size in terms of body mass, or size in terms of
> wing area?  My hunch 
> > (without having access to more information) is
> that the authors were 
> > referring to mass.  If so, that would imply that
> the Guillmots and 
> > razorbills have larger wings than penguins of
> similar mass.  If so, it 
> > is to be expected that when swimming, they would
> stroke at a lower 
> > frequency than penguins, due to the additional
> loading on their 
> > relatively larger wings.
> 
> I also suspect that is what they mean, though I'll
> have to go grab the 
> actual paper to confirm.  One thing I do find odd in
> that summary is 
> that the mass overlap between penguins and alcids is
> rather minimal; 
> the guillemots in my dataset range from 906 grams to
> 1177 grams.  
> They're among the largest alcids; razorbills are
> only slightly larger.  
> The smallest penguins, on the other hand, fall at
> about 1.3 kg.

The largest living and flying alcids; the maximum
possible wing loading with which Neornithes can still
achieve active flight is fairly exactly 23 kg/sq m,
IIRC. Flightless wing-propelled alcids ranged from
roughly 1.5kg (Mancalla milleri) to ~5kg (Great Auk).

FWIW, Flying Steamerducks (2.5-3kg) are not
exclusively marine and not exclusively diving (and in
that, probably far more foot- than wing-propelled
divers... as was Chendytes), but they probably closer
to flightlessnessness without actually reaching it
than other living aquatic birds.

Did the study include diving-petrels?

> Interestingly, penguins rank as the most efficient 
> fully homeothermic swimmers.  I cannot remember the
> proper reference for that bit of information right 
> off the top of my head, but I have a copy of the 
> paper stored away here and I'll send the citation
> along to this thread when I dig it out.  I believe 
> efficiency was measured as mass-specific fuel 
> consumption per unit distance.

I remember that too - wasn't some East German guy
working on this back from the late 80s onwards? Lowest
drag coefficient; some military researchers for a time
(mid-90s) pondered whether it would be feasible to put
"bills" on their submarines to reduce noise (and in
diesel subs, fuel consumption)

Regards,

Eike




        
                
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