See for abstract C 1338 a (or ty study develops a method for the prediction of the effects of car traffic on the density of breeding birds in the Netherlands. The study shows that a reduced density of breeding birds adjacent to motorways is a common phenomenon. An effect on density could be assessed for about two-third of the investigated species in woodland and in open meadow landscape. In order to quantify this effect, the density is related to the noise level. Noise level being an indication of traffic concentration. By using this relationship, the "effect distance" (the distance from the road up to where a reduced density is present) and the decrease of the density is calculated. The effect distance is largely determined by traffic density. The amount of woodland along the road diminishes the effect distance. The maximum and minimum "effect distance" figures are provided for woodcock, cuckoo, coot and black-tailed godwit. The decrease of the density in the disturbed zone indicates that the quality of the habitat along roads is lowered. On the other hand, it is observed that the effect on breeding bird density decreases with a growing population size. The use of density as an effect variable implies that the influence of the road will reach further than the measurements show. Interpretation of the results indicates that the decrease of density is caused by road traffic noise. Stress may play an important role. The results of the study can be used to accurately predict the effect of road traffic on breeding bird populations, and also for other habitats than woodland and open meadow landscape. Finally, the study presents possible mitigating and compensating measures.
Abstract