Re: Island-dwelling dinosaurs (was Re: Gargantuavis neck vertebra)

[Dr Ronald Orenstein <ron.orenstein@rogers.com>]

The native hen is still significantly larger than its nearest cousin, the 
Black-tailed Native Hen of the mainland (which can fly). However, there are 
certainly examples of very small flightless rails (including the extant 
Inaccessible Rail) and flightless passerines (the extinct Stephens Island 
Wren). Neither of these face (or faced) native terrestrial predators (unless 
the wren was hunted by the possibly carnivorous adzebills (Aptornis)).

Ronald Orenstein 
1825 Shady Creek Court
Mississauga, ON
Canada L5L 3W2

On 2012-06-18, at 8:38 PM, Tim Williams <tijawi@gmail.com> wrote:

> Mike Keesey <keesey@gmail.com> wrote:
> 
>>> Well, they're all not flightless, and at least secretarybirds and seriemas
>>> still roost in trees a lot, IIRC even nest there. No time to look up the
>>> hornbills.
>> 
>> I meant as the still-flying-but-can-deal-with-other-critters-on-the-ground
>> phase.
> 
> 
> Yes, that's what I meant too.  If a bird is predominantly terrestrial,
> and can deal with terrestrial predators (including protecting its
> eggs), then it might actually be advantageous to lose flight.  Flight
> is not only energetically expensive, but it also constrains body mass.
> 
> 
> Nevertheless, as the Tasmanian nativehen demonstrates, you don't
> always need to get big.  For the nativehen, if you're small and intend
> to stay on the ground, it helps to be fast.
> 
> 
> Brian Lauret <zthemanvirus@hotmail.com> wrote:
> 
>> What we consider to be normal weaknesses and behaviour for flightless bird
>> on islands may not be particularly applicable to flightless birds that evolve
>> on continents, rarer though they may be.
> 
> 
> Yes, nicely put.
> 
> 
> Large, flightless, continental birds are rare now; but as your post
> makes clear, they were all the rage in the Paleogene.  Some, like the
> dromornithids and phorusrhacids, survived until quite late in the
> Neogene.  Ratites are still with us in Africa (but not Madagascar),
> South America and Australasia.
> 
> 
>> Clearly, these are birds that like *Patagopteryx* appear to prove both the
>>  'small flightless birds only evolve on islands'-rule and 'continental
>>  flightless birds need to be big to survive'-rule wrong. Likewise, tapaculos
>>   have also been considered flightless.
> 
> 
> Yes, and tapaculos arose in a continental environment.  Nevertheless,
> some tapaculo species are critically endangered.  Nevertheless,
> tapaculos have fared better than island-dwelling passerines that were
> flightless, or nearly so.  One of these, the Stephens Island wren
> (_Xenicus lyalli_) of New Zealand, was famously wiped out
> single-handedly (or single-pawedly) by the lighthouse-keeper's cat.
> However, it appears that more than one introduced cat was behind the
> extinction of this songbird.  In any case, the latter evolved in the
> absence of terrestrial predators, and so was vulnerable when feral
> cats came along.
> 
> 
> 
> 
> 
> 
> Cheers
> 
> Tim