Seasonal variation in numbers and habitat selection
of the Common Crane (Grus grus)
in an agricultural area in Southern Sweden

Mikael Hake, Petter Kjellander, Inga Ahlqvist & Maria Levin

Abstract.   We studied the variation in numbers and habitat selection of the Common Crane within a 460 km2 large agricultural area in southern Sweden during 1996-1998. As the number of Cranes has increased in Sweden during the last decade, the damages made on different types of crops by the birds have become an increasing problem. To reduce damages and enhance conservation of the Swedish Crane population, it is essential to learn more about seasonal variations in numbers and habitat selection, particularly in the agricultural areas, which suffer most from crop damages. Mean maximum number of Cranes in the study area increased from the arrival of the first birds in late March until a peak of about 1000 birds was reached during the second half of April. About 300 birds were then observed regularly from early May until late July. From early August, the number of birds increased and reached a peak of about 2500 in late September. Thereafter, numbers gradually declined until all birds had left in early November. The Cranes utilised newly sown cereal fields to a high degree from late March to late April, then almost exclusively fed in marshy areas until early June, when they switched to use potato fields to a high extent. From mid-July, they mainly utilised marshlands and pasture fields, but as stubble-fields started to appear from late August, after the harvest of the cereal fields, they switched to use this habitat almost exclusively during the rest of the autumn. The results suggest that crop damages could be reduced significantly by careful planning of the farming in combination with scaring birds away from the most vulnerable crops. If conservation should be successful, however, it is important that sufficiently large areas are set off as refuges for the Cranes during the entire season.


Head of the Project:
Dr. Mikael Hake
Grimsö Forskningsstation/Grimsö Wildlife Research Station
SE-730 91 Riddarhyttan
SWEDEN
E-mail: mikael.hake@nvb.slu.se
  
 

 

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