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Evolution of avian wing shape

Ben Creisler

A new paper:

Xia Wang & Julia A. Clarke (2015)
The evolution of avian wing shape and previously unrecognized trends
in covert feathering.
Proceedings of the Royal Society  B: 282 (1816)
DOI: 10.1098/rspb.2015.1935

Avian wing shape has been related to flight performance, migration,
foraging behaviour and display. Historically, linear measurements of
the feathered aerofoil and skeletal proportions have been used to
describe this shape. While the distribution of covert feathers,
layered over the anterior wing, has long been assumed to contribute to
aerofoil properties, to our knowledge no previous studies of trends in
avian wing shape assessed their variation. Here, these trends are
explored using a geometric–morphometric approach with landmarks
describing the wing outline as well as the extent of dorsal and
ventral covert feathers for 105 avian species. We find that most of
the observed variation is explained by phylogeny and ecology but shows
only a weak relationship with previously described flight style
categories, wing loading and an investigated set of aerodynamic
variables. Most of the recovered variation is in greater primary
covert feather extent, followed by secondary feather length and the
shape of the wing tip. Although often considered a plastic character
strongly linked to flight style, the estimated ancestral wing
morphology is found to be generally conservative among basal parts of
most major avian lineages. The radiation of birds is characterized by
successive diversification into largely distinct areas of morphospace.
However, aquatic taxa show convergence in feathering despite
differences in flight style, and songbirds move into a region of
morphospace also occupied by basal taxa but at markedly different body
sizes. These results have implications for the proposed inference of
flight style in extinct taxa.