Abstract

The departure behaviour of northward migrating Bar-tailed Godwits and Red Knots was studied on Farewell Spit, New Zealand, from 8–27 March 1994. Most flocks left in the evening and on rising tides. An exception occurred when waders responded to weather conditions favourable for migration, having had their departure delayed by strong winds for the previous five days. On average, flocks left with a slight tailwind, although some left with headwinds of up to 12 km h ^–1 . Most departures occurred after the passage of a low-pressure system or at the approach of a high-pressure system, which produced favourable southerly winds. Despite observed departure directions being intermediate between those expected for flights to either northern Australia or northern New Zealand, most flocks probably encountered easterly winds from high-pressure systems and flew to Australia with some wind assistance. Varied assumptions of flight speed and the level of protein deposition show that flight range estimates can differ so widely that predicting migration routes is difficult.