on 10/16/02 4:50 PM, Bob Parcelles,Jr. at [log in to unmask] wrote:

> The darters [and anhingas] do
> NOT in any way need to spread their wings to dry them.

Really... why not?

A wet wing is certainly heavier than a dry wing, and will require more
energy to move during flight.  Spreading the wings must let them dry faster
than keeping them folded.  To the extent that flight is hindered by wet
wings, spreading them to hasten drying will be advantageous.

Again, if we are correct that cormorants and anhingas/darters are sister
groups, they inherited the spread-wing behavior from a unique common
ancestor, along with their peculiar wettable feathers.  They did not evolve
these characteristics independent of one another.  The wings of both
cormorants and anhingas dry more quickly when spread.

Let's assume for the sake of argument that anhingas/darters do somehow
benefit thermally by spreading their wings -- this would be a secondary
advantage of the behavior, overlain on (but not replacing) the original
function: wing-drying.  In an evolutionary sense, wing-drying would be,
quite literally, the primary function (even in this scenario).

David Wright
Miami Shores

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