The contour feathers of water birds exhibit adaptations to the impact forces of diving, plunging and alighting

Abstract

Abstract: The 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.