Gaast, one of the fifteen godwits fitted with a satellite transmitter this spring in Friesland, has come to grief in Mali. After a breeding season in the Frisian meadows, the bird flew to Guinea-Bissau in June via Spain and Senegal. After a stay there of about three months she continued her flight to the inner delta of the River Niger in Mali. There she met her end in a fishing net. This has been revealed by data transmitted by the satellite and from a search in the wild by staff of Wetlands International.
Gaast’s transmitter fell silent about a week after she arrived near a small fishing village in Mali. The only signals still getting through were from the so-called ‘temperature and activity logger’.
Because the transmitter indicated that the bird had to be dead, a search action was set up as quickly as possible with the help of Wetlands International in Mali. That was no sinecure as Gaast had travelled to a virtually inaccessible part of the delta. Skipper Sine Konta, who knows the delta like the back of his hand, and Wetlands International colleague Mori Diallo were able to reach this remote spot.
It took them a few days to locate the transmitter – a bright yellow ball, about the size of a small egg, that is implanted in the birds’ abdominal cavity. They first had to gain the trust of the villagers. Initially, the fishermen pretended they’d never seen the transmitter. Once the transmitter research had been explained in detail, and with the help of the village elder and his advisors, the satellite transmitter was finally located and handed over.
Surveys conducted by researchers from Wetlands International and Altenburg & Wymenga Ecological Research Bureau in the inner delta region around the turn of the century revealed that in this area many birds are caught in nets by specialized bird catchers. In the south-western corner of the Delta, where Gaast met her end, birds are usually shot. But the local fisherman who showed Mori and Sine where he had found the godwit told them that she’d got caught in his fish trap. It hadn’t been a deliberate hunt but pure bad luck. The village fishermen do not actually hunt for birds on a regular basis. Only if the fish catch is poor, towards the end of the fishing season, do they try to catch some birds for their own consumption.
We’ll never know now if Gaast was flying a so-called loop migration route. One of the questions that the transmitter research is hoping to answer is whether godwits fly in a circle. It looks like some of the godwits that fly south from Friesland via Spain and Portugal to West Africa return north after the winter via a more easterly route through Mali and Italy.
The research has already taught us that godwits have rather flexible strategies for their migration and overwintering. For example, godwit Nijhuzum did not make the same stopover in the rice fields of Spain that Gaast did. The two birds then did spend some time close to each other in the key area for overwintering godwits in Guinea-Bissau. From there they unexpectedly left in completely different directions: Gaast flew eastwards to Mali (1200 km) while Nijhuzum flew back a bit to the Senegal River (500 km), on the border between Senegal and Mauretania. These varying routes raise the question of whether the rice fields in Guinea-Bissau were perhaps unable to offer enough to the overwintering birds this year.
At this moment in time only five of the fifteen radio godwits are still transmitting – mainly due to mechanical failure. If all goes well, they will continue to transmit signals until early April, just long enough to provide information about the migration back to Friesland.
The transmitter project is a joint project of the University of Groningen, the Alaska Science Center of the US Geological Survey, Altenburg & Wymenga ecological research bureau and the Nederland-Gruttoland coalition. The project is supported financially by the Department of Knowledge of the Ministry of Agriculture, Nature and Food Quality and the Province of Friesland. The birds can be followed via www.vogelbescherming.nl/grutto
Further information: - Jan van der Kamp or Eddy Wymenga, Ecological Research Bureau Altenburg & Wymenga, tel. 0511-474764, e.wymenga altwym.nl
- Jos Hooijmeijer, University of Groningen, J.C.Hooijmeijer rug.nl
- Prof. Theunis Piersma, University of Groningen, T.Piersma rug.nl
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