Godwits readying for Alaska migration

March 7, 2008

A new cohort of godwits is preparing to leave Miranda, the second wave to have their epic 11,000km journey to and from Alaska monitored by satellite technology. Dr Phil Battley, of the University’s Ecology Group, is leading the New Zealand leg of the worldwide project run by the US Geological Survey.

Dr Battley says that this year six females and three males have had transmitters fitted. Last year, the team used satellite tracking to watch the progress of 16 godwits. The return of female E7 in September was the first complete journey tracked, including outward legs from the Firth of Thames to Yalu Jiang nature reserve in China and on to the Yukon Delta and their breeding grounds in Alaska, then returning in a record 11,700 km flight across the Pacific.

Birds monitored this year were captured using mistnets across a shallow pond at Miranda. Although the group hoped to tag more males, the female birds appeared easier to catch, Dr Battley says.

“We caught about 100 birds the first night. The females appear to come in first and be less agile, so they don’t tend to avoid the nets so easily. The males were weighing in at about 420g and will be up to about 500g by the time they leave, with females increasing from 300g to 600g before they leave.”

Dr Brett Gartrell of the University’s Wildlife Health Centre assisted with the 30-minute surgery to implant a transmitted on each of the nine birds. The tiny device is fitted in the bird’s abdominal cavity, with general anaesthetic surgical procedures including heart monitoring and aspiration taking place. All the birds caught were banded, so even those not tracked will be more easily identified in future.

Dr Battley says that the internal transmitters are being used this year because in 2007 the backpack transmitters used for some birds appeared to limit the ability to migrate.

“Last year the males weren’t tracked successfully, probably because of their external transmitters. The aim this year is to track the males to confirm they are doing the same thing as females and to follow the six females again as a control, in case the wind conditions or something else are different and have an impact.”

The first godwits are expected to leave within the next two weeks, arriving in Alaska from the end of April where they will stay until the end of August, returning to New Zealand in September.

“What they are now doing is hanging out in Miranda getting nice and fat,” Dr Battley says, “with changes to their internal organs including an enlarged heart allowing for this huge journey – they will effectively take off for seven days of non-stop exercise.”

Dr Gartrell has also assisted in surgery to install transmitters in a sub-species of godwit in northwest Australia. This population goes through the Yellow Sea to eastern Russia.

“No one has previously tracked this group to Russia so we know little about the routes they take,” Dr Battley says. “Do they return back the same way after breeding or do they refuel in Russia and make a single big flight from Russia to Australia?”

Both monitoring projects are part of the Pacific Shorebird Migration Project funded by the Packard Foundation, contracted to US Geological Survey and PRBO Conservation Science. Massey University is a collaborating partner.

Information on the project and a satellite track of the godwits travel can be found at:
http://alaska.usgs.gov/science/biology/shorebirds/barg.html

Source: Massey University