- The aim was to investigate the impact of power lines at Shotton (North Wales) on waterbirds wintering on the lagoons and on birds crossing the power lines to reach nearby habitats.
- Systematic observations were made of all waterbirds attempting to cross the power lines. Their direction and height of flight, together with weather variables were recorded. Surveys were also made of the ground beneath the power lines in order to look for casualties.
- In total, 3,957 birds were observed crossing the wires. Wildfowl and Gulls were the most frequently recorded groups of species. Frequency of crossings peaked in September for all species groups except Gulls which peaked in mid-winter. Gulls, Wildfowl, Cormorants and Herons tended to cross in smaller groups than Waders. Half the observations involved birds flying straight over the power lines and making no use of the lagoons.
- The main directions of travel were related to the birds' feeding and roosting areas. The majority of birds of all groups crossed the power lines above the top earth wire, and only a small proportion were recorded flying either through or beneath the power cables. Up to 3.8% of birds came within 1 m of the cables. The spans to the north-west of the lagoons were crossed most frequently.
- One Mallard wing was found beneath the power lines but it was not known if this was a collision casualty or not. One Mute Swan was seen to strike the power lines and fall but survived and one diverted at a late stage, this represents 14% of the species seen to cross. In general, mortality rate of waterbirds due to collisions with wires was considered to be low.
- The impact of the power lines on the mortality rate of waterbirds at Shotton is discussed.