Study finds that godwits on time

A Massey University student has discovered that bar-tailed godwits are hard-wired in their flight times when taking part in their extraordinary annual 30,000km return journey between New Zealand and Alaska.

PhD ecology candidate Jesse Conklin has published a paper in the international on-line science journal Nature Communications revealing data from light-sensitive geo-locators that tracked the depature of 16 godwits on their annual Alaskan pilgrimage and their precise return six months later.

Mr Conklin's study revealed that godwits departing New Zealand first were also the first to arrive back – a finding he says is remarkable given that the godwits span out across a wide space in Alaska and may experience very different conditions and breeding success.

"We knew that a given breeding site might have a narrow optimal arrival window to ensure breeding success, but this shows that even southbound migration is tightly-scheduled," he says.

The study strongly indicated the migratory birds' rigid timing was hard-wired, because they time their migration perfectly to arrive in Alaska just as melting snow makes their nest sites available.

"[This is] an event that could hardly be predicted by cues available to godwits in New Zealand nearly two months previously," he said.

The two-year project involved capturing birds from a small population of 200-280 godwits at the Manawatu River estuary in Foxton and attaching leg-mounted, light-sensitive geo-locators before they departed in March and early April.

The study suggests a biological predisposition for an optimal breeding arrival date as the primary driver of variation in the migration schedule.

He says his findings also highlight the potential impact of climate change on migratory birds.

- © Fairfax NZ News