Re: T.Rex Feather Skepticism

[Michael Habib <mhabib5@jhmi.edu>]

Auks actually vary a fair bit in the degree of motor ability at 
hatching; the only really precocial forms are some murrelets.  However, 
they nearly all nest on remote cliffsides, so they are not 'ground 
birds' in the same way that I meant in my previous post.  As Denver 
Fowler already pointed out, seabirds such as pelecaniforms and 
procellariforms have altricial young, but also nest in remote 
locations, such as islands or cliffsides (granted, pelecaniformes is 
likely not monophyletic, but the point still holds).  Ground-living 
parrots are probably the best example of altricial ground birds, and 
they presumably are altricial because of phylogenetic constraints.  The 
question there would be whether the offspring are less altricial than 
most parrots.  Other recently flightless lineages might also be a good 
place to look.  Galapagos cormorants are presumably still 
semialtricial, though they may be more precocial than most comorants.

Secretary birds nest on elevated platforms (mostly in small trees), so 
they do not count as 'ground birds' from a nesting standpoint, though 
they certainly are ground feeders.  They might be expected to be 
slightly less altricial than most falconiform birds, but I do not have 
any good life history data on them handy at the moment.  The ecological 
equivalent in S. America would be Seriemas, and I do believe the 
offspring in that case start hunting on the ground with the parents at 
a relatively small body size, and might be considered somewhat 
precocial (but again, I need to check the literature to confirm that).

Oh, and penguins are either labeled as semiprecocial or semialtricial, 
depending on who you ask (and what system you use).  Generally, the are 
highly dependent on care and some warmth from adults, but they can walk 
well from an early age, thus they maintain the common (but hardly 
fixed) pattern of ground-nesters generally having young that are mobile 
early.  Also, from a feeding standpoint, penguins are much more akin to 
volant birds.  That is, the young are under selection to grow rapidly 
and attain the ability to fly (subaqueous flight, in this case), in 
order to feed themselves.  This follows the other common (but again, 
often broken) pattern that birds which require flight to feed 
independently are somewhat more altricial (in comparison to animals 
like grebes, loons, ducks, grouse, etc).

--Mike Habib

On Thursday, September 15, 2005, at 04:22 AM, Brian Lauret wrote:

> I believe that finfoots hatch very altricial, though the parents do 
> take them in those wing-pouches of course..what about penguins and 
> petrels by the way? Auks? Or don't they qualify as ground-birds? 
> Kakapo also hatch altricial,as do ground and night parrots..hey! here 
> we might have real altricial ground birds! Perhaps secretary birds 
> could also be included?
>
> Brian