Roadside hedgerows and trees as factors increasing road mortality of birds: Implications for management of roadside vegetation in rural landscapes

The 26-month study was carried out in 2001–2003 on a network of 15 roads (48.8 km) with different traffic volumes (350–10,500 cars day−1) and varying structure of the surrounding landscape in farmland of south-western Poland. A total of 862 road-killed birds were recorded. The most abundant group was made up by urban species (50.2%), followed by hedgerow specialists (30.3%), woodland birds (7.7%) and those associated with open areas (3.8%). The total shares of the three most numerous victim species (Passer domesticus, Passer montanus and Hirundo rustica) amounted to 79.3%. The mean (±1 S.E.) yearly number of casualties per 100 m of road calculated for 15 roads reached 0.91 ± 0.20 for all groups, 0.44 ± 0.14 for urban birds, 0.28 ± 0.07 for hedgerow specialists, 0.06 ± 0.02 for woodland species and 0.03 ± 0.01 for birds of open areas. For the three commonest species the values were as follows: P. domesticus 0.40 ± 1.37, H. rustica 0.07 ± 0.03 and P. montanus 0.13 ± 0.05. A disproportionately high mortality was recorded near tree belts, hedgerows and built-up areas, while it was much lower in open farmland. Traffic volume had a clear negative impact on the mortality of P. domesticus and woodland species. In order to limit the losses among birds due to vehicle traffic the spontaneous bushy vegetation should be removed from the immediate road vicinity. New hedgerows should be made “safe” for wildlife by planting them further away from the roads, i.e., along dirt roads, watercourses and ditches.