Since last week, 15 black-tailed godwits in Fryslân (in the north of the Netherlands) have been flying around with tiny transmitters in their abdominal cavities. The transmitters were inserted during a minor operation by the American vet Daniel Mulcahy and his Dutch colleague David Tijssen. With the help of the transmitters, researchers will be able to track the birds for about a year in their breeding grounds in Fryslân as well as during their migration from and to Southern Europe and Africa.
"We hope that this unique project will tell us more about the exact migration route of this threatened wader," says research leader Professor Theunis Piersma of the University of Groningen.
For a number of years now, several bird species in the Netherlands have been flying around with small transmitters, including Montagu’s Harriers, purple herons and lesser black-backed gulls. "With these species the transmitter is secured onto the bird’s back with a harness, but with a small species like the godwit, which also travels great distances, that is not the best option," says Piersma. "'Outboard transmitters' could affect the streamlining of the godwit and a harness could become too tight when the birds fatten up in preparation for the migration. Luckily implantable transmitters have now become so small that we can use them for our research into the migration of adult birds, which after the breeding season may migrate in one non-stop flight from the Netherlands to areas south of the Sahara."
The transmitters weigh 26 grams, including the aerial. In a minor operation in a mobile operating theatre in the field, the transmitter is introduced into a ‘airbag’ in the abdominal cavities of the birds. "That airbag is part of the birds’ breathing apparatus," explains Dan Mulcahy. Experience has shown that you can insert a sterile transmitter there without any problems arising. Mulcahy is a vet with the Alaska Science Center of the US Geological Survey. Since 1993 he has introduced several thousand transmitters into about 34 animal species, ranging from birds of prey to polar bears. "The technology is developing at top speed," says Mulcahy. "Currently, the godwit is the smallest animal species in which transmitters can be implanted." The transmitter is linked to the French Argos satellites.
Although Piersma is convinced of the safety of the system, this research has caused him a few sleepless nights. "You’re making a bird that hasn’t asked for it undergo an operation. You don’t do that without first thinking long and hard about it and holding many discussions. Eventually, we concluded that the end justified the means. Once we know where the godwits recoup their strength on their migration from and to their wintering grounds, the protection of these birds outside the Netherlands can be better coordinated."
Ninety percent of the Northwest European population breeds in the Netherlands, but between 1975 and 2005 this population decreased by 65% due to the enormous intensification of agriculture. Since 2006 the black-tailed godwit has been on the IUCN world list of threatened species and is now one of those on the Red List.
The transmitter research is a joint project of the University of Groningen, the US Geological Survey in Alaska, ecological research bureau Altenburg en Wymenga in Feanwâlden and the coalition Nederland-Gruttoland and is supported financially by the Department of Knowledge of the Ministry of Agriculture, Nature and Food Quality and by the Province of Fryslân. The godwits with transmitters can be followed from 1 June on http://www.grutto.nl.
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