A collar with a GPS logger on it has saved the life of a greylag goose from an Alterra trial.
Bang in the middle of the number 3 on the while collar is a round hole. A bullet hole, says researcher David Kleijn with conviction. He has seen holes like this before in leg rings on geese. 'Science saved this goose's life. If that collar hadn't been there, the bullet would have gone right through its neck. It wouldn't have survived that.'
The goose in questions is one of 21 that were fitted out with a collar carrying a GPS logger in June 2010. The aim of the trial is to find out as much as possible about the whereabouts of graylag geese. Kleijn: 'We want to get an idea of the geese's use of space. That will enable us to design the landscape so as to minimize the problems caused to farmers by the geese.'
The loggers register exactly where the goose has been. That information is sent every day at set times, as long as the apparatus can pick up a signal from an antenna in the area. So the trick is to be close enough (within 200 metres) at the right moment to collect the data. Sending it out continuously takes too much electricity, says Kleijn by way of explaining the rather circuitous procedure. This way, the logger's batteries last about a year.
Most of the 21 geese were already 'home and dry' when the batteries gave out, explains Kleijn. 'A couple of them died, a couple of them disappeared. Last year we caught three of them and this was the fourth.' Kleijn got hold of the goose thanks to a report from a fanatical bird ringer from Wieringen. 'He saw two logged geese in a group of 800-900 geese in the Westerlanderkoog. Later I got reports on the website geese.org as well.'
That was the end of May, before the moulting season. 'But if they are around then they will still be around during the moulting season.' So he set off two Saturdays ago to catch the geese. He succeeded in catching one of them. The exciting part will be seeing what information the whole operation delivers. 'The data have not yet been extracted. We hope that the logger wasn't hit directly, because then we won't have any data at all.'
According to Kleijn it is not likely that the goose was an easy target on account of the logger. 'Those yellowish white collars are not very noticeable. They are almost the same colour as the goose's breast. What is more, hunters in the area were sent a letter expressly asking them not to shoot at logged geese. But that is not the last word of course.'