Nine migrant Whooper swans hit power distribution lines - veterinarians initially feared avian flu for mass deaths

Most bird fatalities are caused by cars

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By Pyry Lapintie
     
      Last week at least nine migrating Whooper swans (Cygnus cygnus) crashed into power distribution lines and died near Lake Anerio in the town of Salo in Southwestern Finland.
      After finding several dead swans, even the authorities were alerted, as fears rose that the cause of death might have been avian influenza.
     
The first medium to report on the dead birds was the local newspaper Salon Seudun Sanomat on Monday.
      ”On Thursday I already counted seven dead swans at the scene. I went to pick them up at the request of the Regional State Administrative Agency. They were taken by taxi to the Finnish Food Safety Authority in Helsinki for examination”, says Anna Nordström, the town veterinarian in Salo.
      The dead swans could easily be spotted from cars that were passing by on Highway 1 between Helsinki and Turku.
      On Friday, Nordström received a phone call reporting that two further dead swans had been found, though not in quite the same location.
      ”I have seen one or two dead swans there even previously, but never so many”, Nordström notes.
     
”That is why we began to wonder what could be the cause of death. The birds were collected in accordance with the avian flu protocol. Later on, it was established that the deaths had been caused by sternal fractures and burns. Apart from that the migrating swans were in perfectly good health”, Nordström reported.
      ”When I went to local homes to make enquiries, the residents said that on Wednesday evening lights had begun to flicker in the houses. It must have been the time when the birds struck the power lines”, Nordström assumed.
     
Manager Risto Laurila, in charge of Fortum’s power distribution network in Southwestern Finland, notes that attention has been paid to dangerous places.
      He has never heard anything like this from anywhere else.
      ”Dangerous places include those where large birds set off or come down. We will now investigate whether bird protection balls should be installed here, too. It is likely, if so many birds have struck the wires and come down”, notes Laurila.
      Special researcher Jarmo Koistinen has reported on the deaths of birds on power-line collisions to the Ministry of the Environment.
     
Both power cables and electric wires are hazardous to birds, but according to Koistinen, the local electric wires of 10/20 kV are the most dangerous ones.
      ”They are thinner, which is why a bird does not automatically see them. In addition, such wires are closer to each other. Sometimes large birds are electrocuted when their broad wings touch two conducting wires at the same time”, Koistinen explains.
      Clumsy and large fliers crash into wires more often than do smaller birds.
      Agile birds are capable of swerving at the last moment, but the greatest risks occur in thick fog or at night.
     
”One of the factors behind these deaths of swans in Salo must have been the thick fog that started at Easter”, Koistinen believes.
      In thick fog and misty conditions, even an entire flock of birds could have hit the power lines with fatal results.
     
The Whooper swan does not as a rule winter in Finland, but flies south to the North Sea and Baltic Sea coastline and to Germany, to return in the spring to nest here.
      It is Finland's national bird, and also features on the country's one-euro coin.
     
     
FACTFILE: Most bird fatalities are caused by cars
     
A total of approximately 200,000 bird deaths result from collisions with power distribution lines in Finland every year.
     
Only fewer than one bird per wire-km dies annually, but there are several hundred thousand kilometres of electric wires in Finland.
     
Large birds are at the greatest risk in those resting places of migratory birds that are located near high-voltage power lines.
     
Cars pose by far the greatest risk to birds. According to some studies, the annual number of birds killed by cars in Finland is three million.
     
     
Helsingin Sanomat / First published in print 13.4.2010


Links:
  Whooper Swan (Wikipedia)

PYRY LAPINTIE / Helsingin Sanomat
pyry.lapintie@hs.fi