The recovery of a dead bird
One of the most important
parts of this study is the end of the life of a kite. Survival and causes of
mortality are some of the main focuses.
To find out if one of our tagged birds died, every third day we check all the loggers that we have flying around. The GPS positions send by SMS tell us if a bird is still moving or not. Additional information on temperature and activity make it a bit easier to assess if a bird is still alive.
On the 8th of January it was my turn to 'check the birds'. A very interesting thing to do because you really get an insight in the movement patterns of the kites, who's migrating and in which direction? Who’s all day long in its territory and who goes to a communal roost? and of course; are there any birds that died? Which was the case this time, an adult female with transmitter SWIK40. On the 4th of January it woke up at a communal roost, 9,5 km from it's territory where it usually spend the days. At 6 o-clock the transmitters temperature was still 22 degrees and the value for activity 303, but at 12 o-clock it dropped drastically to 11 degrees and 18 activity. What happened between these two points? To get an insight in that it is important to find the dead corps.
So I jumped in the car to drive to the location which is 30 minutes driving from home, convinced that I would find the bird, or its remaining’s quite easily.
The last points of SWIK40 after the bird died; the 4th of January till the 8th of January.
About one-and-a-half hours later I left the forest patch again without the bird/transmitter but a lot of question marks. I only found a couple of body feathers at four places; just enough to be sure that the bird is dead and didn’t just lose its transmitter. The only explanation I could give for the fact that the bird disappeared was a fox/badger den in the center of the last GPS points. So that afternoon I installed two camera traps close to the den, in the hope to record the fox or badger when it drags the dead kite around.
Today (10-1) I went back to the place because the transmitter still send points after I searched for the kite, which means that the logger must be on the surface. This time I tried to look just for a lose transmitter instead of body parts and feathers, ending up scanning every square meter around the fox/badger den. Finally I stumbled upon the dead kite, perfectly covered under a layer of leafs, still completely intact, but the head missing!
Swik40 before and after removing the leafs that covered the cadaver.
The remaining’s still weighted 1216 grams which is a very vital weight, meaning that starvation can be excluded. What the cause of mortality can be will be further examined by a forensic pathologist; we'll get more info on that later.
The life of female SWIK40:
In 2016 we found her nest on which she successfully raised two chicks. This couple was by far the most aggressive one of which I climbed the nest in this season. The female was captured and tagged successfully that year. One of the 2016 chiocks is still alive and stationary in Switzerland at the moment of writing.
In 2017 this couple was one of the latest ones to start breeding. Two chicks were raised successfully. Both are still alive, one overwintering in Spain and the other one in France at the moment of writing.
SWIK40 female, with her two chicks in better times. Her dark grey bill doesn't points toward a very old individual. Both chicks are overwintering abroad at the moment of writing, one in Spain, the other one in Southern France.
To find out if one of our tagged birds died, every third day we check all the loggers that we have flying around. The GPS positions send by SMS tell us if a bird is still moving or not. Additional information on temperature and activity make it a bit easier to assess if a bird is still alive.
On the 8th of January it was my turn to 'check the birds'. A very interesting thing to do because you really get an insight in the movement patterns of the kites, who's migrating and in which direction? Who’s all day long in its territory and who goes to a communal roost? and of course; are there any birds that died? Which was the case this time, an adult female with transmitter SWIK40. On the 4th of January it woke up at a communal roost, 9,5 km from it's territory where it usually spend the days. At 6 o-clock the transmitters temperature was still 22 degrees and the value for activity 303, but at 12 o-clock it dropped drastically to 11 degrees and 18 activity. What happened between these two points? To get an insight in that it is important to find the dead corps.
So I jumped in the car to drive to the location which is 30 minutes driving from home, convinced that I would find the bird, or its remaining’s quite easily.
The last points of SWIK40 after the bird died; the 4th of January till the 8th of January.
About one-and-a-half hours later I left the forest patch again without the bird/transmitter but a lot of question marks. I only found a couple of body feathers at four places; just enough to be sure that the bird is dead and didn’t just lose its transmitter. The only explanation I could give for the fact that the bird disappeared was a fox/badger den in the center of the last GPS points. So that afternoon I installed two camera traps close to the den, in the hope to record the fox or badger when it drags the dead kite around.
Today (10-1) I went back to the place because the transmitter still send points after I searched for the kite, which means that the logger must be on the surface. This time I tried to look just for a lose transmitter instead of body parts and feathers, ending up scanning every square meter around the fox/badger den. Finally I stumbled upon the dead kite, perfectly covered under a layer of leafs, still completely intact, but the head missing!
Swik40 before and after removing the leafs that covered the cadaver.
The remaining’s still weighted 1216 grams which is a very vital weight, meaning that starvation can be excluded. What the cause of mortality can be will be further examined by a forensic pathologist; we'll get more info on that later.
The life of female SWIK40:
In 2016 we found her nest on which she successfully raised two chicks. This couple was by far the most aggressive one of which I climbed the nest in this season. The female was captured and tagged successfully that year. One of the 2016 chiocks is still alive and stationary in Switzerland at the moment of writing.
In 2017 this couple was one of the latest ones to start breeding. Two chicks were raised successfully. Both are still alive, one overwintering in Spain and the other one in France at the moment of writing.
SWIK40 female, with her two chicks in better times. Her dark grey bill doesn't points toward a very old individual. Both chicks are overwintering abroad at the moment of writing, one in Spain, the other one in Southern France.
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