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Orenstein's pedestrian arguments.




To my point that the almost total absence of flightless birds in the
small-animal niche reflects the non-competitiveness of this body plan,
Orenstein replies:

> Mr Bois, I am tired of repeating the same things over and over.  You are
> NOT right about that.  Flightlessness doesn't enter into it when the birds
> do not, as part of their daily activity, fly much or at all...

Surely this needs justification!  Is he really suggesting that flight is
not important for flying birds?  Again, flight is an expensive facility.
Rails living on oceanic islands (the family owes much of its diversity to
haphazard, but winged, dispersal patterns) lose the ability to fly very
quickly (in evolutionary terms).  The most widely accepted reason for this
is that fueling and maintaining big wings and muscles is affordable only
if flight is essential.  On predatorless oceanic islands they are not
essential and so at times of food shortage a flightless bird would need
less food.  It would therefore be less likely to starve.  The other idea
of flighted birds being blown off islands seems fanciful to me.

        In any case, since rails quickly evolve to a flightless state when
flight is non-essential, it seems reasonable to suggest it has some value
when they have not.  Of what possible value could flight be to a rail?

1. Accounts I have read of rails say that they fly when flushed from
cover.  They only seem to do this as a last resort.  But, as a last
resort, it is probably adaptive.  Many creatures have facilities they
don't use as part of their "daily activity".  I think Orenstein is taking
a simplistic view of rail behavior here.  The ability to cope in
rare emergencies is as critical an adaptation as routine behavior.
Clearly, rail species that live where there are mammals and snakes _need_
to be able to fly.

2. A flighted rail has a greater selection of nesting sites than a
flightless bird.  Many birds are happy to spend their day to day existence
in places they would not nest.  Thomas Martin has done a study which shows
that birds that were thought to lay eggs in consideration of foraging (I
think Lack suggested this) were actually siting nests to avoid predation.
This would be an especially important consideration for a bird which lives
among the mammals and snakes!  Again, I am arguing that the dino-morph
doesn't work well in the small animal niche.  But the dino-morph, the
non-*&%#@-avian dinomorph, DOESN'T HAVE WINGS.  I am happy to agree that
the rail is a furtive and agile forest liver.  But part of its bag of
survival tricks is flight.  Perhaps, rather than huffing and puffing so
much, Orenstein could enlighten us to why _he_ thinks the rail maintains
its ability to fly in these places. 

>...and there are
> PLENTY of birds that compete perfectly well, thank you, on continents and
> continental islands, as thicket skulkers or terrestrial stalkers in
> forests.  Rails, pittas, antpittas, mesites, tapaculos, rail-babblers,
> buttonquail, some partridges and true quail, trumpeters, etc etc etc!!!

Take out the birds that can fly, and take out birds that operate in
habitats with an open forest floor (such as trumpeters), grasses and
marshes...and then we'll talk.

> Mr Bois, I really hate to say this, and I don't want to get personal, but
> it truly seems to me that you have little knowledge of the natural history
> of living animals in general, or that if you do you utterly refuse to
> recognize it when it contradicts with your preconceived notions.

Here is my preconceived notion: dinosaurs of the late cretaceous got
bigger.  There was none smaller than a chicken.  There must have been a
reason for this.  I think this quote from John McLoughlin's _Synapsida_
can enlighten: "Represented by the rodent-like multituberculates,
marsupials, forest-bottom insectivores, and tree-dwelling primates, these
furry creatures shared with a growing number of birds the art of being
small and living in micro-habitats in which larger animals could have no
interest." 

        The "larger animals" here are of course dinosaurs.  But surely
McLoughlin is being colloquial.  Rather than having no interest,
dinosaurs lacked the _abilty_ to reenter this niche.  This was because
other animals did it better.  To suggest that dinosaurs could not radiate
into these niches out of choice denies such well established theories as
character displacement, niche partitioning.  SMALL, NON_FLYING,
EGG-LAYING, BIPEDAL animals were indeed excluded from those micro-niches
of the late cretaceous.  THEY ARE ALSO EXCLUDED TODAY.  But really,
Orenstein, these are not preconceived notions, they are facts.

> There are MANY forest and thicket rails in the tropics of South America,
> Africa and Indonesia.  You are undoubtedly reading about North American
> species.  Read about the African flufftails of the genus Sarothrura,
> Rallina forest rails of southeast Asia, and many others.

I am happy to learn this.  Is it possible in your world to impart
knowledge without pomposity?  Is it possible for you to accept
that others may not know as much as you about certain things without
hurling abuse at them?  Knowledge should be a gift.  You use it as a
knife.

> I can't really imagine why such a creature WOULD WANT TO "outrun" a rat,
> and in fact in such dense environments both quadrupeds and bipeds are far
> more likely to rely on staying still and avoiding being noticed than on
> speed when it comes to avoiding predators.

This is, of course true.  But mammals (dogs, for example) can catch lots
of certain rails.  Presumably escaping through the air, clumsy though it
may be, makes a marginal, but critical difference. But there _are_ animals
with a different body plan and no flight that can evade extinction causing
levels of predation.  Relative to a biped of equal mass, a quadruped
can dig better burrows (is it only the kiwi which digs burrows), can slip
under lower horizontal stems, climb into smaller holes (by the way, Darren
Naish commented that the expression "thin as a rail" comes from the
ability to slip through close cover.  What he didn't mention--I'm not
saying he was holding it back--is that the species to which this refers is
laterally compressed and is suitable for grass: it is a marsh species),
and can be closer to the ground for a given rate of speed. Relative to a
biped of equal mass, a snake can pass through much narrower holes, can
take advantage of holes in the ground, can lay its eggs in inaccessible
places...

>  Manoeuverability counts too.
> Again you are ignoring the nature of these environments and the creatures
> that live there.  

I think this is the area we need to look.  Quoting from Betty Cunningham's
post: "fern and briar and brush and gorse and other plant-like nouns that
sound short make a far denser ground cover than mere grass can."  We can
argue all day and night about rails' abilities.  Why could no dino-morph's
make it here, in these micro-niches?  I'm not sure rails are a valuable
analogue at all, in this instance.

I said:  If bipedalism was no impediment to dinosaurs in close-cover,
why do you think they were excluded? 

I meant: If bipedalism was no impediment to dinosaurs below the
chicken-threshhold, why do you think they were excluded from these
micro-niches?

This is the prime question you need to address.  I have addressed it.  You
don't like my ideas.  WHAT ARE YOURS?

> Rails are highly-adapted, successful birds found on every
> continent but the Antarctic, with 143 extant species in 34 genera.  They
> are superbly adapted for getting about in dense undergrowth - otherwise why
> do you think they have survived at all?

I don't have any argument with this.  I repeat, no argument.  But, where
they coexist with mammals and snakes (are Guam rails flightless?)
they must also be able to fly (in nearly all cases).

> I realize that my suggesting that
> you lack the facts to back up your claims may seem impolite, but it is
> highly frustrating to see you continuously make claims about the natural
> history of living animals that have not the slightest basis in fact.
> Whether you think rails are clumsy or not is irrelevant - anyone who has
> spent any time with them (and there are some on this list besides me who
> have) will tell you this is utter nonsense.

This is utter nonsense.  Cruel, utter nonsense.  I have never said rails
were clumsy.  I have said their body plan has limitations--all body plans
do.

> "Rails often walk with strong, precise strides.  Being accustomed to cover,
> they often move continuously without long pauses for visual orientation,
> pausing mainly to feed.  When moving through low vegetation, they slip
> beneath low horizontal stems or arched projecting roots, or raise the feet
> high to step over such obstacles... In dense cover rails are adept at
> walking, or even running, without causing any noise or movement of the
> vegetation.  When reacting to alarm, they melt quietly and rapidly into
> cover, often lowering the head and stretching out the neck, as they
> compress the body to allow easy passage through the stems....

For our purposes this generic description of rails is imprecise.  For
example, we need to know how low are the branches relative to those an
insectivore can hide under, what sort of habitat are we talking about
exactly.  Are they talking about a marsh environment (probably) or what?

 
> "The wide distribution of the family is a reflection of the ability of
> rails to adapt to a very diverse range of habitat types.....  The ability
> to capitalize on this great diversity of habitats throughout the world
> indicates that the family shows great adaptive plasticity.... "
> 
> Not a word about awkwardness, falling over their own feet, etc. Okay?

Nor none from me either.  But they are _not_ as well adapted to this
micro-niche as are mammals, lizards, and snakes.  This is true because
they must keep their wings in order to escape it!  I imply no inferiority
by this.  Indeed, for all we know, rail-morphs may well have squeezed the
non-avian dinos out of this sort of habitat.  This would be a true measure
of its inapplicability as a dino analogue!