Alberta Claw <email@example.com> wrote:
> A new paper with suggested implications for the origin of flight in Mesozoic
> D.D. Chin and D. Lentink (2017)
> How birds direct impulse to minimize the energetic cost of foraging flight
> Science Advances 3: e1603041
> DOI: 10.1126/sciadv.1603041
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Yes, the paper is replete with implications about how arboreal
foraging behavior might have promoted flapping flight in "protobirds"
(including _Archaeopteryx_ and _Microraptor_). The idea is that a
small lift contribution from an incipient/partial wingbeat
("proto-wingbeat") could have significantly extended long jumps
between branches, and thereby increase foraging gain. This is one of
the few arboreal models for the origin of flight that doesn't involve
a passive gliding stage. In this respect, it reminds me of GSP's
"trees up" model (PDW). Chin & Lentink's hypothesis entails a
'flapping-first' model of flight evolution, with the hindlimbs
providing the initial impulse. This is perfectly reasonable.
The major fault I find with this particular model is that it assumes
an arboreal setting. If _Archaeopteryx_ and _Microraptor_ were indeed
leaping between branches, one might expect them to have feet
specialized for perching. They don't. The hallux is only modestly
descended on the metatarsus, and it's certainly not reversed. So it's
difficult to envisage how an arboreal foraging protobird would land.
Take-off is fine. But without a foot that is adapted for grasping
branches, the landing would be highly problematic. It's not like the
hands could be deployed to gain purchase during the landing, given
that they'd be fully occupied with flapping immediately prior to the
For small bipeds like _Archaeopteryx_ and _Microraptor_, a much more
viable model would involve a terrestrial flapping-start (also
hindlimb-driven) rather than arboreal. These short aerial leaps could
be used to clear obstacles on the ground; this would be especially
useful to small terrestrial bipeds living in cluttered environments.
Arboreal foraging is entirely tenable for more crownward avians that
have clear arboreal/perching adaptations but weak flight abilities,
such as _Sapeornis_ and maybe confusiornithids. But I think it's a
non-starter for more stemward taxa (_Archaeopteryx_, _Microraptor_,
_Anchiornis_, etc) that lack any evidence of perching ability.