1. Supplementary Text: Complementary Feather Scales and Functions from The Feather’s Multifunctional Structure Across Nano to Macro Scales Inspires Hierarchical Design

To complement the review, here we provide a fuller picture of the feather's relevant biological scales and functions. Specifically, we examine how feathers form the wing planform to shape a streamlined aerodynamic surface (Section 1). Then we explore how different lengthscales contribute to unique physical attributes found in feathers including coloration (Section 2) and the mechanical properties (Section 3) required for flight.