On the Multifunctionality of Feathers and the Evolution of BIrds

Abstract

The ability feathers have to perform many functions simultaneously and at different times is integral to the evolutionary history of all birds. Many studies focus on single functions of feathers; but any given feather performs many functions over its lifetime. Here, we review the known functions of feathers and discuss the interactions of these functions with avian evolution. Recent years have seen an increase in research on the evolution and development of feather functions because of an increase in high quality fossils with preserved feathers, new tools for understanding genetic mechanisms of feather development, new tools for measuring and analyzing feather color, availability of phylogenies and phylogenetic comparative methods, and an increase in interest in feather molt. Here, we aim to review how feather functions interact with avian evolution, with a focus on recent technological and discovery-based advances. By synthesizing research into feather functions over hierarchical scales, we aim to provide a broad context for how the adaptability and multifunctionality of feathers have allowed birds to diversify into the astounding array of environments and life-history strategies. Overall, we suggest research into avian evolution that involves feather function in any way should consider all aspects of a feathers’ functionality, including multiple functions, molt patterns, ecological/mechanical interactions, and feather wear over time. With this more holistic view, processes such as the evolution of avian coloration and flight can be understood in a broader and more nuanced context.

Cerebral Polymorphisms for Lateralisation: Modelling the Genetic and Phenotypic Architectures of Multiple Functional Modules

“…While those scaleless chickens undoubtedly could not fly, neither do they really contribute much to an understanding of the evolutionary origins of bird flight, except to suggest that the protein FGF20 is important in creating vertebrate skin appendages, including feathers and scales. Feathers are highly multi-functional, helping with flight, but they are also involved with water-proofing, buoyancy, protection, balance, avoidance of parasites, camouflage, mimicry, eye and orifice protection, sexual display, male-male competition, distraction, odour production, moulting and renewal, prey capture, and migration, which together as a set resemble a pleiotropy [406]. Birds differ from one another with a DNA-based phylogenetic tree available for 198 species [407], most of which can fly, but a number of which have lost that ability.…”

Cognitive and Neurophysiological Models of Brain Asymmetry

“…While those scaleless chickens undoubtedly could not fly, neither do they really contribute much to an understanding of the evolutionary origins of bird flight, except to suggest that the protein FGF20 is important in creating vertebrate skin appendages, including feathers and scales. Feathers are highly multi-functional, helping with flight, but they are also involved with water-proofing, buoyancy, protection, balance, avoidance of parasites, camouflage, mimicry, eye and orifice protection, sexual display, male-male competition, distraction, odour production, moulting and renewal, prey capture, and migration, which together as a set resemble a pleiotropy [406]. Birds differ from one another with a DNA-based phylogenetic tree available for 198 species [407], most of which can fly, but a number of which have lost that ability.…”