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Re: T.Rex Feather Skepticism



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