Meeting Abstract
Linking predictable, repeatedly observed evolutionary patterns in morphology to their functional implications is vital to understanding how and why those patterns have evolved. Here we use multiple datasets to link evolutionary changes in flight morphology to their ecological drivers and functional implications. We have found that across the avian tree, bird species restricted to islands tend to evolve smaller flight muscles and longer legs than their continental relatives. This predictable evolutionary pattern is strongest on small islands with fewer predators. The relaxation of predation pressure may lead to a shift to a Bauplan less suited for rapid takeoff. However, the precise functional implications of these morphological changes for takeoff and flight are not well known. We tested how these morphological differences affect flight performance using a novel comparative dataset of takeoffs for 16 species from five orders, ranging body size from 4.1g to 130g. Both across and within species, birds with larger flight muscles reached faster peak take-off velocities and exhibited a greater reliance upon the wings relative to the leg thrust during takeoff. We conclude that when island bird populations evolved smaller flight muscles and longer legs, it resulted in a shift toward leg-dominated take-off mechanics, reduced takeoff velocity, and reduced capacity to escape from predators.
