Re: feather asymmetry

[Mike Habib <biologyinmotion@gmail.com>]

On Jul 7, 2014, at 2:38 AM, Sam Horus <sam.horus@gmail.com> wrote:

> Putting aside full powered flight for a moment, does this also mean that 
> other aerodynamic advantages of feathers, such as running up near vertical 
> slopes, is impeded until 4:1?

Not necessarily. Behaviors like wing assisted incline running might be brief 
enough that feather torsion is of less concern. There are also other ways of 
reinforcing feathers (such as overlap) which allow some living birds to fly 
well with less asymmetric feathers - this could apply to WAIR, too. Some doves 
have primary feathers with vane ratios around 2.5:1. In those species, the 
distal feathers don’t separate during flight, so presumably feather torsion is 
not an issue.

Experimentally, Ashley Heers has data showing that young birds with symmetric 
feathers can engage in WAIR, so we know that asymmetric feathers are not 
required. Whether or not they would perform better with asymmetric primaries is 
unknown. I suspect it would not have much effect since feather torsion looks to 
be pretty limited in the high speed video captures (but that’s just eyeballing 
it, don’t give that too much credence).

Cheers,

—Mike


Michael Habib
Assistant Professor of Cell and Neurobiology
Keck School of Medicine of USC
University of Southern California
Bishop Research Building; Room 403
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Research Associate, Dinosaur Institute
Natural History Museum of Los Angeles County
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