Radio-marking cranes in northern Sweden

A Co-operation project of the SCWG (Per Hansson and Ulf Skyllberg¹),
with Crane Protection Germany (Simone Röper and Günter Nowald²) and 
UCM (Prof. Dr. Javier A. Alonso³)

1  Swedish Crane Working Group, Västerbotten, Sweden
2  Kranich-Informationszentrum, Gross Mohrdorf, Germany
3  Facultad de Biología, Universidad Complutense, Madrid, Spain

 

It is already well known that most of the Swedish colour banded cranes -which belong to the southern populations (south of Lake Hornborga)- do winter in southwestern Spain. But it is also true that some Swedish cranes, specially those from northern latitudes, may use the central flyway to go to Hungary and will probably winter in Tunisia. On the other hand, routes of Swedish cranes from different origins may cross each other: Some birds from western Sweden may fly over Öland island and Rügen-Bock area to go to southeast, over the central flyway, while other birds from eastern Sweden may go to Spain, using the western flyway. The limit between these two populations could be fixed by means of radiotracking. 

Also nothing is known on habitat use and territory size of northern crane families. To solve these questions we marked the first three young cranes with radio-transmitters in Västerbotten-area in Northern Sweden in summer 2001. The area is covered by the snow from the late October to Mai. Both in spring and autumn the area is very important for migrating birds from northeastern Europe up to Siberia. Nearest city is Umea.

Between 26th July and 1st September we (PHa, USk and SRö) did the first research work on radiotagged cranes in Northern Skandinavia. On 26th July we fitted the first two young cranes with radiotransmitters:

Red-Blue-Red / Red-Black-Red     (frequency 149.842 MHz)  –  locality Innertavle/Västerbotten,    63°49/ 20°23
Red-Blue-Red / Red-Black-Green   (frequency 149.992 MHz)  –  locality Sarsjöliden/Västerbotten, 64°02 /19°36  

On 10th August after a long time without success we got the third young, more than 4kg weight and almost flying:

Red-Blue-Red / Red-Black-Blue    (frequency 149.892 MHz) – locality Abyn/Västerbotten, 63°57/20°27       

Additional we marked 5 young more, only with colour rings. 

We (SRö, Daniela Tiede) did a preliminary research on habitat use and territory size of all three crane families by means of radio-tracking during July and August. By this method we got a lot of interesting and completely new results. Data are still being prepared. At the beginning of September all three families remained in their breeding territories. During migration we (Crane Protection Germany) search for these radiotagged cranes on several resting places in Northeastern Germany. As well as we do about radiotagged cranes from Germany and Estonia, we will analyse the staging duration and habitat use at different resting places.

All young were much thiner than those marked in Germany -at seven weeks of age they weighted just about 3 kg-. S. Röper did the radiotracking with all three families. Sometimes fieldwork was quite hard: cranes went up at 3:15h in the midnightsun. But it was so exciting and interesting and we learnt so much!. Anything was new. We got quite good data on habitat use and territory size by radio-tracking each family 4 whole days, even after fledging. Afterwards the birds were only tracked some hours during their activity period. Nevertheless we got a lot of interesting observations. It is possible that the young are so thin due to the scarcity of available food with animal protein. The dropings content was only blueberries! And some families stay obviously all the time in the bogs and the forest, and after fledging they went out to the meadows at greater distance. We think in the poor bogs there is not so much food with animal protein available (we have to continue doing some research in this direction in the next years). The radiotracking did also show that the cranes used clearcuts - probably more than dense forest. We think that both insects and berries are more abundant in the clearcuts: a lot of unsolved questions!. If there were some meadows or barley-fields inside the territority, the cranes used to feed there. Barley is often on very swampy peat-soil with some frogs and worms. And it was nicely extensive - there were many more plants other than barley; and the barley itself was only 30 cm high. Harvest was in the beginning of September.  Immediatly if the barley is ripe (yellow) the cranes preferred to feed on the grain in the uncutted barley-fields.

Apart from the radiotagged families we could observe all banded cranes from year 2001 (and one from 2000) - they all were still alive! And it seemed that they did not worry about their transmitters, and everything with the transmitters was OK. S. Röper was really happy about this first results: everything had been done in the right way.

Apart from the breeding cranes we could find some nonbreeding cranes and later some gathering places too. When Simone went back to Germany, the radiotagged families still stayed in the breeding territories. Therefore she was not able to find out when they leave and where they gather. We really hope that crane work in this area can be countinued in next years. There are many questions to be answered, and we want also to extend our area farther north.

All these Swedish birds, as well as those of German, Estonian or Polish origin, will be searched for by JAA from an aircraft over the Spanish wintering area of the species.

Acknomledgements.-   We wish to thank Mr. Armand Nestler for financial support to buy the three radio-transmitters. We also acknowledge Spanish airforces for collaboration with the project providing military aircraft and pilots through a research contract with the Universidad Complutense de Madrid.  

 

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