Some time ago we informed about our dataloggers being used in the project on research of the biotop preference of the Polish Red Kite population, led by researchers of the University of Life Sciences in Poznan. This year 21 juvenile birds were tagged and they all headed for the Iberian Peninsula during their autumn migration. We went to Spain in order to test whether we can find a tagged bird in the field.
We spent this one week's trip together with the scientists whose main objective was to research the Red Kites' wintering biotops. Thanks to the data gathered by means of the dataloggers it was possible to select areas where the birds spent longer periods of time. We managed to visit several such places. Another aspect of scientific value was to define possible threats. Also here dataloggers come handy - lack of signals would mean either a technical failure or some problem with the bird. As two of the birds stopped sending signals already in November without any technical problems detected, we decided to visit those places hoping to find some explanation. In such cases time is a major factor and usually only prompt actions can bring answers to the problem. Unfortunatelly we came too late to be able to name any causes. However the scientific part of the journey was very fruitfull and the data gathered will help to define optimal wintering biotops enabling conservation measures to be taken in order to preserve the species.
We were particularly interested in practical possibilities of finding a tagged bird. As the target we chose a juvenile Red Kite which stayed for a longer period of time in central part of Spain. The device was configured to gather the data every 2 hours and send them as a package of 5 datasets via the mobile network. So in practice the data acquisition frequency equalled 10 hours, which at this time of the year meant once a day. In order to find the bird this configuration required relatively early changes. Two major aspects need to be considered in such cases. The first is the mobile network range - it is always possible that the bird would come to a place with no mobile network coverage thus preventing the signals to be sent on time. The other is the weather - setting the configuration for higher frequency too soon in bad weather conditions would mean discharging the datalogger's battery and a break in data transmission in an inappropriate moment. Fortunatelly we did not have to worry for the latter, as the battery was fully charged and we had sunny weather during the whole stay in Spain. In this respect two days earlier we successfully changed both configuration parameters. From this moment the device recorded the data every hour and sent only 1 dataset in a packet, so directly after recording it. It turned out that the Red Kite chose to stay in the vicinity of the Monfrague National Park, so we went there reaching the town of Torrejon in the evening, only 13 kilometres away from the bird's roosting place!
We started the day with an early breakfast and another configuration change. Now we set it to it's full power - registering and sending the data every 15 minutes. After the breakfast and right after the sunrise the new configuration was successfully accepted (the "Aquila" dataloggers send confirmation information), so we packed our bags and after 20 minutes of driving we reached our destination point. The roosting place turned out to be hillocks covered with grass and sparce oak trees, used as pastures for sheep. This makes a perfect opportunity for raptor species to survive as dead sheep are usually left in the field providing apropriate food supplies. The only difficulty for us was that the surrounding was cut by high fences, making reaching the exact point impossible. However we found a gate and decided to take the risk. 200 meters from the point we found some buildings which turned to be a farm owned by Mr. Miguel. To our surprise he spoke fluently English and gave us the permission to continue our searching. We spent the next hour wandering around and looking out for our bird from a hill, checking the latest coordinates on a laptop. We expected that in this sunny weather our Red Kite, as perfect glider as it was, would soar in the sky when frightened away. The time passed by and every consecutive coordinates proved we should be seeing the bird. Our eyes however denied this fact. Slowly we began questioning the accuracy of the data as it seemed impossible that the bird would Sparrowhawk-wise fly low between the trees. It turned out the bird did exactly that, finally emerging from between the trees after an hour and 15 minutes of observation, enabling the documentary photos to be taken and proving the accuracy of the datalogger.
Satisfied with the meeting we said goodbye to Mr. Miguel (Thank you very much!) and spent the rest of the day in the valleys of the Monfrague National Park, with open mouth admiring the wonderfull landscapes around us and hundreds of magnificent vultures above our heads.