KAHLERT J (2002) A bridge between Sweden and Denmark: a bridge too far for birds?. LIMOSA 75 (3): 129-129.

Theme Day 'Birds and scale new infrastructure'

The effects of construction of the 'Fixed Link' between Denmark and Sweden, a combination of a bridge and a tunnel, on birds in the surrounding areas have been studied. Creating a new island where bridge and tunnel meet was one of the works carried out. In the bird sanctuary on the nearby island of Saltholm several bird species were within reach of expected effects of these works. In particular, Saltholm holds internationally and nationally important bird populations, such as 5000-6000 breeding pairs of Eider Somateria mollissima, a moulting population of over 7000 Greylag Geese Anser anser and 2000-3000 moulting Mute Swans Cygnus olor. Indirect effects, mainly from sediment spilling during construction, on e.g. mussels and seagrasses (Ruppia and Zostera), could also affect local bird populations.
      The environmental monitoring project was preceded by a stage in which quantitative criteria were set. If effects would exceed these criteria, compensating measures would be obligatory. For instance, as one of the possibilities, it was considered to reduce hunting pressure in a wintering area known to hold mainly Saltholm Eiders, if the breeding population would decrease more than 15% during construction of the Fixed Link. Although difficult to calculate - and difficult to agree on beforehand - the principle of considering mitigation beforehand in case predefined criteria would be transgressed is a unique feature, which might be an example for similar projects elsewhere.
      Eiders showed a steady decrease during construction, reaching the critical 15% value. However, a detailed analysis showed that the Fixed Link was not the cause of the decrease on Saltholm. Construction work caused little disturbance to Greylag Geese during their most sensitive moult period. For Mute Swans, distance to the newly created island turned out to be important, and displacement effects could be shown. However, there was also an interaction with food supply (underwater vegetation), which was reduced during construction possibly as a consequence of the severe winter of 1995/96.
      Generally, it was concluded that the construction did not have large scale negative effects on bird populations in the areas surrounding the bridge and the new island. However, an incident in which migrating songbirds collided with the bridge, apparently attracted by the lights on the bridge, has subsequently triggered new awareness to bird collisions at huge constructions.

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