Water balance during real and simulated long-distance migratory flight in the Bar-tailed Godwit

We examined Bar-tailed Godwits (Limosa lapponica), a long-distance migrator y shorebird, for evidence of dehydration toward the end of their 4,300-km m igratory Right from West Africa to the Dutch Wadden Sea. Bar-tailed Godwits are ideal subjects for research on Right range constraints because they ca n readily be caught in migratory flight. Because godwits are capable of lon g nonstop travel, we hypothesized that they are physiologically adapted to minimize en route water loss, and therefore, do not experience water imbala nce under standard migratory conditions. To test this hypothesis, we compar ed the hydration state of flying Bar-tailed Godwits at the end of a long bo ut of migratory flight to that of recently-landed godwits. Flying godwits w ere hydrated to the same degree as birds with free access to water, suggest ing that godwits maintain water balance during migratory Right. To corrobor ate these empirical results, we ran a theoretical simulation of Right-incur red loss of water and energy in a male Bar-tailed Godwit based on the publi shed model by Klaassen et al. (1999). When a low body drag is assumed, mode l output suggests that Bar-tailed Godwits Eying at altitudes ranging from s ea level to 3,000 m will avoid dehydration, and that flight at about 3,000 m will result in the longest possible flight range.