Physiomorphic Transformation in Extreme Endurance Migrants: Revisiting the Case of Bar-Tailed Godwits Preparing for Trans-Pacific Flights

In a 1998 paper entitled “Guts don’t fly: small digestive organs in obese bar-tailed godwits,” Piersma and Gill (1998) showed that the were tiny fat loads huge individuals suspected of embarking on non-stop flight from Alaska to New Zealand. It was suggested prior migratory departure, these godwits would shrink used during fuel deposition boost size capacity exercise optimize performance. Here we document verity proposed physiomorphic changes by comparing organ sizes body composition Limosa lapponica baueri collected modesty midway their fueling period (mid-September; fueling, n = 7) with previously published data for had just departed trans-Pacific (October 19; flying, 9). Mean total masses two groups nearly identical, but half mass consisted water, while constituted over flying godwits. The also differed fat-free components. heart muscles heavier godwits, components relatively greater fraction contrast, related digestion homeostasis most larger compared These results reflect functional importance muscle energy acquisition consequences flight-related exertion extreme apparently occurred short time window (≤1 month). We conclude inferences made basis correct. cues stimuli which moderate remain be studied.