Quick Dips

Space-Age Petrels

Satellites, sea birds and science have come together in a Lincoln University research project based in the Department of Entomology and Animal Ecology.

The work is part of a PhD study by Amanda Freeman on the foods and foraging ecology of the Westland Petrel. She's looking at the relationship between the petrels and fisheries activity off the West Coast -- particularly the hoki fishery, as that has an impact on the petrels' traditional feeding grounds.

Westland petrels breed only between Punakaiki and Barrytown and the population is enjoying a burgeoning food source -- fish offal from fleets operating off the West Coast and in Cook Strait. This has been linked to a general increase in the population of the birds, but at the same time it also has implications for their future survival if fishing practices change.

By satellite tracking, Freeman and supervising ecologist Kerry-Jayne Wilson have set out to chart exactly where breeding petrels go and for how long. Because of the distances from shore flown by the birds, radio telemetry was not feasible, so the scientists turned to satellites.

With the help of technician Alastair Freeman, Freeman and Wilson attached borrowed satellite transmitters to two male petrels. The tiny 35-gram transmitters, taped to feathers on the birds' backs, have now started doing their job of transmitting to polar orbiting satellites 800 kilometres overhead. In turn these satellites send the data to a processing centre in the US, from whence it makes its way to Lincoln.

"This is the first time seabirds smaller than an albatross have been tracked at sea and the results obtained during the last two weeks have surprised us," says Wilson.

"Those first birds did more or less just what we might have expected. Both spent four days at sea before returning to feed their chicks. One, Sandy, fed 100-150 kilometres west and southwest of their breeding colony at Punakaiki. The other, Paul, travelled similar distances west and northwest of the colony. Paul was allowed to carry his transmitter on a second trip and that time he was away a week and headed south, and at one point he was just offshore from Haast."

Another bird, Spot, was tracked initially feeding off Cape Foulwind, then he went north to the latitude of Cape Farewell where he took advantage of a strong northwest wind and travelled to Cook Strait.

The flight from Farewell to Cook Strait, over 350 kilometres, was made in just four and a half hours. Spot spent six days doing a circuit -- Cook Strait, Palliser, south to the Mernoo Bank (150 kilometres east of Cheviot) then south to the Chatham Rise (at which time he was much closer to Lincoln University than his home at Punakaiki), then back to Cook Strait via Kaikoura. He took just a day to fly around the coast to Karamea and two days later he was still feeding just west of Karamea oblivious of the anxious ecologists awaiting his return at Punakaiki.

"Spot has now travelled well over 2,000 kilometres in nine days, a greater distance taking in far more locations than we ever imagined for a single foraging trip."

Once the transmitters are recovered, the batteries will be replaced and they will be deployed again. Then it's back to the drawing board to raise funds to purchase more transmitters for next season.

The importance of the work is spelt out clearly by Wilson.

"The study is an investment in the future of one of our endemic seabird species and satellite telemetry is the only way to obtain the detailed data we need on where birds feed at sea and their relationship to fishing vessels."