Abstract: T he contour feathers of water birds are well-known to
show structural details in their distal one-third that optimally confer
water repellency and resistance to water penetration. In this study,
these details were further examined to see if they also provide
resistance to the impact forces of diving and alighting. To this end, 49
species representing 37 water bird families were grouped into nine
foraging niches before measurement of length, diameter, and spacing of
their barbs. Twelve land bird species grouped into two foraging niches
were included in this study for comparison. These measurements allowed
the calculation of the ranges and medians for barb stiffness and vane
deflection for each foraging niche. A phylogenetic ANOVA approach was
followed to determine if the foraging niches for water and land birds
explain differences in feather microstructure while accounting for
phylogenetic relationships. There were no significant group aggregations
for water or land birds confirming the statistical reliability of the
ANOVA approach.
Differences between the deflection parameter medians of water and land
bird foraging niches proved significant demonstrating an evolutionary
distinction between these groups. No such difference was observed for
the two land bird foraging niches indicating similarity in feather
structure. For the water birds, significance was found among all aquatic
niches showing that differences in feather microstructure are associated
with respect to differences in aquatic feeding niches.
These findings support the notion that evolutionary adaptations of
feather traits are significant across bird species and their respective
foraging niches. The observed mechanical and morphological variations of
feathers are therefore considered adaptations to different habitats and
behavioral patterns.
Keywords water birds, contour feathers, water penetration,
impact forces, diving, foraging niches.