Griffon Vulture Igor is one of the vultures who has been in the satellite tracking program for some time. Igor was released on 7.9.2019. with satellite transmitter (more about that here… »). He fit in well, often staying at the restorant for vultures, as recorded by video surveillance cameras.
20.11. he also visited Mileševka, where the “Emergency” situation happened. According to the data we follow daily, we have noticed that on the 20.11. between 6 and 8 in the morning something significant happened to the transmitter. Most likely the teflon strap was broken. The “xyz axes” of the accelerometer changed abruptly, which clearly indicated that the position of the device, which was on the back of the bird, had suddenly changed and was hanging. Another parameter confirming this change is the sudden drop in temperature registered by the transmitter to just 10C. When the transmitter is on the bird and the condition is regularly the temperature it shows is 20-36C. However, we also knew that the transmitter did not go down and that Igor was moving, surprisingly, very well. He flew over Uvac and behaved normally for the next 28 hours.
We closely followed the events and on the 21.11. at 12 o’clock, the transmitter stopped moving, the temperature was practically ambient (from -2 to 15C, depending on the time of day). The “xyz axes” of the accelerometer indicated that the transmitter was partially facing the ground. Sunlight was well received by the solar panel, and the batteries were charging normally, again indicating that the device was not in too dense vegetation. As there was a possibility that the bird had fallen too, we immediately alerted the Rangers of JP “Reserve Uvac” and sent them the coordinates.
We had the coordinates, but also the difficulty that the transmitter was partially turned to the ground, so GPS “saw” fewer satellites, which meant less location accuracy. The Rangers soon took to the field and were unable to find either the bird or the transmitter.
In order to minimize the location error and try to get the Rangers as accurate as possible to the location where the transmitter is located, we have done so-called. “burst”, that is, taking a large number of GPS points and short time. We eliminated all points that were located with fewer satellites and where HDOP (Horizontal Dilution of Precision) was inappropriate. The rest points were the most reliable.
Soon the Ranger team took to the field again, this time with more precise data and found the transmitter!
Many thanks to our Rangers for their quick action and sacrifice!
It remains for us to study the Teflon strap by which the transmitter binds to the bird and to try to determine what exactly happened, or why the transmitter fell. Igor is probably fine and we are awaiting his next finding at the “restourant” or otherwise.
Frames from the action of finding the transmitter: