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RE: How Pelicans learn to fish



  Or we can take a cue from another direction and say that because the skull is 
deep and triangular, and looks like a stork, it was feeding on larger, more 
selective prey than opportunistic fishing in this manner. Small amounts of fish 
may mean not as much fish feeding, after all (although I am sure we've only 
been able to derive limited information from limited specimens in which limited 
amounts of gut contents are known -- correct me if the sampling is much higher 
in resolution than this). Perhaps *Pteranodon longiceps* was a terrestrial 
carnivore, as Witton and Naish suggested for another very-large-headed 
pterosaur group. Moreover, due to the massively outsized skull of 
pteranodontids, one may assume that head-based strategies for prey acquisition 
were the norm, and that in this realm of comparison that they were incomparable 
to a large number of living taxa (including birds) making comparisons 
problematic (just as the relatively inflexible neck of azhdarchids impairs 
comparison to storks).

  One thing I do not recall (precisely, but may have seen in print somewhere) 
is that the slight upturn to the beak and the outsized length of the upper beak 
to the mandible indicates a functional distinction to some typical pterosaurs, 
which have relatively even lengths in these two cranial segments. Moreover, the 
upturn can indicate "prying" behavior (impairing fossil evidence of meals) -- 
much as has been suggested for *Dsungaripterus weii* -- while the outsized 
upper to lower could actually make the skull effectively a giant signaling 
device, and have very little, if anything, to do with feeding.

Cheers,

Jaime A. Headden
The Bite Stuff (site v2)
http://qilong.wordpress.com/

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


"Ever since man first left his cave and met a stranger with a
different language and a new way of looking at things, the human race
has had a dream: to kill him, so we don't have to learn his language or
his new way of looking at things." --- Zapp Brannigan (Beast With a Billion 
Backs)





----------------------------------------
> Date: Wed, 3 Nov 2010 10:07:12 +0000
> From: Mark.Witton@port.ac.uk
> To: dinosaur@usc.edu
> Subject: Re: How Pelicans learn to fish
>
> "Much has been written and speculated regarding pterosaur flying, but
> what about smacking the water?"
>
> Lots of folks have suggested Pteranodon may have plunged dive, with
> Chris Bennett most recently noting that the skeleton of Pteranodon is no
> more fragile than that of Pelecanus and that diving from heights of 10 m
> or so was possible. However, the regurgitated gut content of Pteranodon
> suggests that pretty dinky fish were being eaten, and Pteranodon has a
> particularly long, narrow skull that may be ill suited to grabbing
> mouthfuls of small fish in a pelican-like manner (indeed, you can ignore
> the many claims that pterosaur and pelican bills are anything alike: the
> little helical jaw joint of pterosaurs does allow for slight expansion,
> but it's a million miles away from the multi-hinged, distensible
> mandibles of pelicans). I wonder if Pteranodon was feeding in a slightly
> more careful manner, perhaps alighting on the water surface or something
> like that.
>
> Mark
>
> Mike Habib 03/11/10 12:41 AM >>>
> No specific ones that I know of, but I haven't looked carefully. In
> both cases the skull is large and largely thinned-walled, but that
> probably isn't a diving correlate, per se. Maybe someone else here has
> looked at that in more detail.
>
> --Mike H.
>
>
> On Nov 2, 2010, at 7:47 PM, Dan Chure wrote:
>
> > Any structural convergences in the skull?
> >
> > Dan
> >
> > On 11/2/2010 5:21 PM, Mike Habib wrote:
> >> The only diving birds that fold back the wings in a "knife" position
> are gannets and boobies (i.e. sulidae). Pelicans actually don't tuck
> their wings all that far back on dives; I doubt it's beyond the normal
> joint excursion for a modern bird.
> >>
> >> One bit of interest, though, is that the ratio of bone wall thickness
> to total bone diameter in pelicans is very similar to that in derived
> pterodactyloids. It's about the same as Pteranodon, for example.
> >>
> >> Cheers,
> >>
> >> --Mike Habib
> >>
> >>
> >> On Nov 2, 2010, at 7:13 PM, Dan Chure wrote:
> >>
> --
>
> Dr. Mark Witton
>
> Palaeobiology Research Group
> School of Earth and Environmental Sciences
> University of Portsmouth
> Burnaby Building
> Burnaby Road
> Portsmouth
> PO1 3QL
>
> Tel: (44)2392 842418
> E-mail: Mark.Witton@port.ac.uk
>
> If pterosaurs are your thing, be sure to check out:
>
> - Pterosaur.Net: www.pterosaur.net
> - The Pterosaur.Net blog: http://pterosaur-net.blogspot.com/
> - My pterosaur artwork: www.flickr.com/photos/markwitton
> >>> Are there any osteological correlates to pelican diving behavior?
> One would be joints that allow the wings to be rotated backwards, but do
> all diving birds do that or does diving occur in other ways in other
> birds?
> >>>
> >>> Dan
> >>>
> >>>
> >>> On 11/2/2010 2:05 PM, Richard W. Travsky wrote:
> >>>> Of course the first thing I thought of was pterosaurs...
> >>>>
> >>>> http://www.nytimes.com/2010/10/26/science/26qna.html
> >>>>
> >>>> Q. How do pelicans learn to dive for fish?
> >>>>
> >>>> A. Young pelicans learn to feed themselves through a combination of
> trial and error, imitation of adult birds and instinct, bird experts
> suggest.
> >>>>
> >>>> In the United States, the Eastern brown pelican (Pelecanus
> occidentalis carolinensis) and the California brown pelican (Pelecanus
> occidentalis californicus) make dives onto schooling fish from
> impressive heights or float on the surface to scavenge fish. A dive from
> 30 to 60 feet up, or even higher, hits the water with considerable
> force. Fish a few feet below the surface are scooped up, and water
> drains from the sides of the pouch. They tilt their heads back and
> swallow on the spot.
> >>>>
> >>>> For young pelicans, some early experience in diving for fish comes
> during their time in the nest, when they graduate from feeding on
> half-digested fish bits regurgitated by their generous parents to
> retrieving fish from the famously capacious pouched parental bills and
> even their gullets. The nestlings may dive in shoulder deep to make the
> parents disgorge fish. Pelicans are well fed in the nest for 9 to 11
> weeks, by which time they are fully feathered and ready to go out on
> their own.
> >>>>
> >>>> Their diving success rate is highly variable and depends on
> experience. Adult California brown pelicans bring up fish from around
> two-thirds of their dives, while novices appear to have a lot of
> trouble; fewer than half survive their first year out of the nest.
> >>>>
> >>>>
> >>>>
> >>>> Didn't know the mortality rate was that high.
> >>>>
> >>>> Much has been written and speculated regarding pterosaur flying,
> but
> >>>> what about smacking the water?
> >>>>
> >>>>
> >>>
> >> Michael Habib, M.S.
> >> PhD. Candidate
> >> Center for Functional Anatomy and Evolution
> >> Johns Hopkins School of Medicine
> >> 1830 E. Monument Street
> >> Baltimore, MD 21205
> >> (443) 280-0181
> >> habib@jhmi.edu
> >>
> >>
> >>
> >>
> >>
> >
> >
>
> Michael Habib, M.S.
> PhD. Candidate
> Center for Functional Anatomy and Evolution
> Johns Hopkins School of Medicine
> 1830 E. Monument Street
> Baltimore, MD 21205
> (443) 280-0181
> habib@jhmi.edu
>
>
>
>