It was with great excitement we set out to the forests in NE Småland to retrieve the data loggers that we deployed in last year´s breeding season. The new (< 2 g) GPS-tags that we used were programmed to enable us to explore various aspects of the nightjars´ non-breeding movement. In addition, we would for the first time see the full migration track of a nightjar with high precision and without these annoying information gaps close to the equinoxes (due to the escalating uncertainty in the latitude component in geolocator-derived position data).
We have been very fortunate and up to now we have retrieved eight GPS-tags which are more than we expected and hoped for. Unfortunately the tags´ batteries did not last as long as anticipated, which is probably to be expected when using cutting-edge miniaturized technology. We are of course very happy with the data provided and are looking forward to analyse it in detail during our long non-field season.
But first we will spend a few more weeks among the nightjars, ringing more birds and deploy new tags!
A nightjar, plenty of coffee and a laptop are crucial components for a successful fieldwork. The latter is used to keep track of all the ringed birds. While many birds stick to their breeding territory and are re-trapped in more or less the same place, others roam around 10s of km. Hence, it is crucial to pick the right bird if you want to get your device back!
This is how a nightjar ringed in Italy looks like. After trapping and approximately 500 nightjars in the last couple of years without any recoveries of birds ringed abroad we were surprised to find a bird with an Italian ring and one male with a German ring within just two weeks.
After a full night of field work I struggled to figure out what was wrong with this ring – it did not look like our Swedish rings used to do. Note the comb-like claw on the middle tow – a structure which function still has not been thoroughly described.