Ardery Blizzards

Mysteries where petrels from Ardery Island go fishing getting solved

"So long, and thanks for all the fish"

The Petrel Weekly #1
- an irregular supplement to the Ardery Blizzard,
the only electronic newspaper from Ardery Island -

Ardery Island, Feb 1999.

The biologists on Ardery Island leave very little left private for the petrels breeding on the island. Love affairs with the petrel next door are closely followed, and they also know when the parents have arguments with their own kids. Fights with the neighbours are often not missed in the biologists' eyes. But high-tech equipment is now used to reveal even more secrets.

Biologists drinking tea...
Artificial nests are installed to provide more information when the biologist are not in the colony. While the biologists are drinking their cup of tea inside their comfortable "apple field huts" a data-logger computer follows the birds in the colony. All birds in the colony are provided with an electronic tag, so the researchers know when which bird is at home. But these artificial nests are also used as "weight-watchers": the nests also records the weight of the bird or chick. So the biologists know how fast the chicks grow and how successful the parents were shopping for food at sea. What food they actually they bring back home from sea is studied by taking stomach samples from randomly chosen birds. But till last month the biologists puzzled their heads where about they went for their food.

Petrels followed even at sea
In January 1999 the bird research on Ardery Island entered a new phase. The biologists started attaching the satellite transmitters onto petrels, breeding in their study areas. The birds are now followed even when they are off the island. On the picture is an Antarctic petrel just fitted with a satellite transmitter. These miniature trackers weigh less than 21g, which is equivalent to a backpack of less than 3.5 kg for a person of 70 kg.

The trackers are attached to the birds in the same way as colleagues of the Australian Antarctic Division have been attaching them to albatrosses and to shearwaters. "The trackers are simply stuck to the feathers with some adhesive tape, " says Jeroen Creuwels, leading the team of bird researchers on the island. "Birds can move their wings freely and after a day most of them seem to forget their extra load on their back. The trackers almost disappear in the feathers, " he says. "And the good thing with tape is that when we remove the transmitters the birds hardly loose any feathers."

Which places are hot for Antarctic petrels?
The satellite data give the biologists an idea where the good fishing spots are for petrels in the Southern Ocean. A rough sketch of the voyages that one of the first Antarctic petrels (A0091) on Ardery Island fitted with a transmitter is given in figure 1. Waldo Ruiterman, "Techno-ass 2", the technical assistant of the Ardery team, wrote in a day a simple program to plot the first raw data. Waldo: "Well, I thought it would be better to write a program, before these biologists start to use coloured pins on a map on the wall". These data are just downloaded from the Argos data-processing center in Toulouse, France. The radio-modem connection with the Australian station Casey enables the bird researchers team on the island to download the data from the flying birds with the trackers.

Jeroen explains: "The Antarctic petrel on the picture is A0091 from nest T033. He was during the first trip almost 5 days away from its chick, before it returned. The second trip was less than 4 days and during the third trip the bird seemed to stay closer to island the island. During the first two trips it spent much time in an area around 250 km North. During the last trip it wandered more around the island on the same latitude, mostly 50 km West of Ardery. The values East of Ardery are probably wrong, but we haven't had time to analyse these data much more thoroughly"

Fish, but not always fresh
"It is not always very fresh food they deliver to their chicks." says Jeroen. He and his crew takes stomach samples by flushing. The samples show that the freshness of the food they bring to their chicks differs greatly between the birds. Jeroen's supervisor Jan van Franeker did flushings on Ardery Island in the late eighties and early nineties. He discovered that the bulk of their food is one species of fish: Antarctic silverfish, Pleurogramma antarctica, and the rest is mainly krill.

So long...
After delivery of their meal the birds leave often within half an hour to collect new food for their demanding chicks. "From the data of the artificial nest-system we can see that a normal meal would be around 160g, which is more than a quarter of it's own weight." That why it takes so long. But the chicks must be grateful for all the fish they bring.

* "The hitchhiker's guide to the Galaxy" is the only book Jeroen managed to finish on Ardery in his season 1997/98. He has good intentions to finish "So long, and thanks for all the fish" by the same autor (Douglas Adams) this season.

Blizzard #12