7 research outputs found
A phylogenetic comparative analysis reveals correlations between body feather structure and habitat
1. Body feathers ensure both waterproofing and insulation in waterbirds, but how natural
variation in the morphological properties of these appendages relates to environmental constraints
remains largely unexplored. Here, we test how habitat and thermal condition affect the
morphology of body feathers, using a phylogenetic comparative analysis of five structural
traits [i.e., total feather length, the lengths of the pennaceous (distal) and plumulaceous (proximal)
sections, barb density, and pennaceous barbule density] from a sample of 194 European
bird species.
2. Body feather total length is shorter in aquatic than in terrestrial birds, and this difference
between groups is due to the shorter plumulaceous feather section in aquatic birds. Indeed, a
reduced plumulaceous section in feather length probably reflects the need to limit air trapped
in the plumage to adjust the buoyancy of aquatic birds. In contrast, the high pennaceous barbule
density of aquatic birds compared to their terrestrial counterparts reflects water resistance
of the plumage in contact with water.
3. Our results show that birds living in environments with low ambient temperature have long
plumulaceous feather lengths, low barb density, and low pennaceous barbule density. Data
also suggest that plumage probably has limited function in reducing the heat absorption of
species living in hot environments.
4. Our results have broad implications for understanding the suite of selection pressures driving
the evolution of body feather functional morphology. It remains to be tested, however,
how other feather traits, such as the density of plumage (feathers per unit area) and the relative
number of different feather types, for example downy feathers, are distributed amongst birds
with different water resistance and thermoinsulative needs