How Did Such Long-Distance Migration Evolve?
Why long-distance migration evolves in the first place is a complex question [30], and the trans-oceanic flights of Alaskan bar-tailed godwits represent one extreme end of the spectrum. It is unlikely that naïve short distance migratory birds accidentally reached New Zealand to establish this migration route, since that would have required excessive “incidental” fat deposits to keep them going for the duration of the flight. Hudsonian godwits (Limosa haemastica) do however visit New Zealand occasionally, but these are already long-distance migrants (albeit less than the bar-tailed godwit) with wintering areas in southern South America and have probably accompanied flocks of bar-tailed godwits in Alaska [12]. As with other seemingly improbable adaptations, it is most likely that the Alaska–New Zealand autumn migration route evolved gradually (Figure 6). One hypothetical scenario is that there was already a long-distance migrating population breeding in Central Siberia and wintering in S
