Record number of voles found in Eurasian pygmy owls’ nesting boxes

Vole population likely to collapse naturally in the spring

print this

”The present vole population is one of the highest on record”, says birdwatcher Arto Tuominen, counting the dead voles which have fallen prey to an Eurasian pygmy owl and been carefully stored in the owl’s nesting box in the municipality of Hauho, part of the City of Hämeenlinna.
      Similar observations have also been made by some other birdwatchers across Finland.
     
The small Eurasian pygmy owl, which weighs in at only around 60 grammes, catches animals that are nearly its own size and tends to store them conscientiously in nesting boxes and natural holes, "for a rainy day", or more accurately for a snowy one.
      Such stocks are necessary as it is impossible to go in search of prey if there is a deep covering of snow on the ground, or if the surface of the snow is hard.
      ”The number of rodents in one box was 229, including mostly field voles (Microtus agrestis) and some bank voles (Myodes glareolus). The voles had been piled neatly with their backs up and their tails towards the centre of the nest box.
     
In spite of intensive forest management, the birds nesting in their holes are doing well, as people have learned how to build bird boxes with sufficiently thick walls, in which owls feel at home, reports Matti Lageström from the ornithological society for the Tampere region.
      Counts to determine the total number of Eurasian pygmy owls in the area have been kept for more than 20 years. At present, the estimated number of these owls is some 100,000 in Finland.
      Would it be worthwhile to place such a bird box in the surrounding forest, in order to keep the voles away from the yard of a summer cottage?
     
”In many places, the current year is the best vole year for 20 years. In fact, the vole population is growing so fast that the owl does not manage to keep up with the pace of the voles’ reproduction. For example, the voles which were born in the summer gave birth to their first offspring in August”, says professor Heikki Henttonen from the Finnish Forest Research Institute (METLA).
      ”The vole population will plummet spontaneously in the course of the spring”, Henttonen notes.
     
Voles belong to nature, but they can also be carriers of a nasty virus infection called Nephropathia epidemica, which is known variously as Puumala virus, or ”Mole fever” or ”Vole fever”. This virus can be contracted by humans from dust to which the virus has spread from the droppings of voles and mice.
      ”One can avoid such a virus infection by chopping wood in woodsheds in such a way that no dust is carried in the air. Voles enjoy being in sheds, and the virus they carry can spread to the respiratory passages of humans from dust”, Henttonen reports.
      Furthermore, in order to prevent infective agents from spreading into the air, one should never vacuum vole droppings from the floor of one’s summer cottage.
     
”The right way to remove such droppings from the floor is to wipe them off using a cloth and a disinfectant”, Henttonen recommends.
      Henttonen himself caught this virus infection while doing some research in the 1970s.
      A total of 3,200 Finns were infected by the Puumala virus last year, setting an all-time record. Two of these individuals died.
      ”Fortunately some 80% of those people who have been infected with the Puumala virus have only few symptoms or none at all”, Henttonen reports.


Previously in HS International Edition:
  Rodent visitor from the north (4.9.2007)
  Significant rise in number of Puumala virus cases in Southern Finland (29.9.2008)

Links:
  Eurasian pygmy owl (Wikipedia)
  Nephropathia epidemica (Wikipedia)
  Finnish Forest Research Institute (METLA)

Helsingin Sanomat