The studies must among other things establish whether a bridge solution would hinder bird migration or constitute a risk to protected species.

Binoculars at the ready
Very extensive research will be carried out as part of the EIA report for a fixed link across the Fehmarnbelt link. This includes visual observations from four stations from where the species of migratory bird, migratory direction and altitude are recorded. On the islands of Fehmarn and Lolland, investigations are being carried out in the area around the planned fixed link’s land area. In addition, migratory birds are recorded from vessels at two stations in the Fehmarnbelt. The investigations are being conducted by specially trained observers who are familiar with Europe’s bird species and their migratory sounds.

Monitored by radar round-the-clock
Migratory birds also fly at night and at altitudes where they cannot be seen with the naked eye or binoculars. They can, however, be monitored by radar. Since 2009, therefore, continuous radar monitoring of the Fehmarnbelt from two land and two marine stations has been carried out. This enables bird migation to be registered on a 24 hour basis. 

To record the height of bird migration, additional vertically mounted radar equipment is being used at five stations which transmits radar beams vertically into the air. This allows bird migration to be monitored at heights of up to 1.5 km. In connection with the investigations into a link across the Fehmarnbelt, radar with narrow beams from former Swiss military depots are also used. Using the focused radar beam, the device scans the skies for moving objects. As soon as such objects are spotted (e.g. a bird or a flock), the target is automatically monitored until it is out of reach. This records migratory direction, altitude and speed.

Two kilometres above the Fehmarnbelt
Where possible, terrestrial birds avoid crossing open waters and prefer the Fehmarnbelt as a migratory route because it is the shortest distance between the European mainland and Scandinavia (the so-called "crow flies line”). A large proportion of Scandinavian breeding stock flies cross Fehmarn and Lolland twice a year. 

Radar monitoring reveals how terrestrial birds that fly by day respond to flying across sea areas. Small birds, in particular, fly at high altitudes as soon as they leave the coast. With radar equipment, it was possible to follow how a flock of small birds fly at heights of up to 2 km after leaving the Lolland coast - as if it was crossing an invisible mountain. The birds probably do this to orientate themselves and find the shortest route to the next landing place. 

Birds of prey use the heated air that rises upwards to gain height over land and then cross a large part of the Fehmarbelt hovering. 

A bridge across the Fehmarnbelt would not present a barrier for land birds. The risk of collision should, however, be assessed and evaluated. 

Water fowl
Water fowl behave differently. As they prefer to fly across water and avoid land areas, a bridge could form a barrier for them. Although the birds can cross land areas such as Schleswig-Holstein on their migration routes to the Wadden Sea or the Southern Sweden land area around Scania to their breeding areas, a bridge could impede migration. The extent to which this is the case is currently being examined at the bridges at the Great Belt, Øresund, Farøsund and Kalmarsund.