2008 Volume 7 Issue 1 Pages 47-57
Road Ecology represents a vast area of ecology from local effects, within the road-habitat, to landscape effects that stem from roads and road networks. Australian roads are generally characterised as narrow strips of remnant native vegetation in agricultural areas. However, some extensive reserves of native forests remain and these habitats like all terrestrial habitats have roads that traverse them. Studies of roads passing through such ecosystems can provide baseline data on how these roads are used by birds and have implications for conservation management. This study investigated easily detected bird species on the roads and their immediate verges of a two-lane highway in continuous Jarrah Eucalyptus marginata forest of south-western Australia. Midway during this two year study 14% of the roadside was cleared, which allowed us to measure the immediate responses by birds. Clearing beside roads hugely reduced the abundance and species richness of birds in the road-habitat. The only species to return to the road-habitat adjacent to forest clearings, during the study, was the Australian Raven Corvus coronoides. Australian Ravens and Grey Currawongs Strepera versicolor were the most frequently detected species (37.6 and 25.5%, respectively). Common Bronzewings Phaps chalcoptera and Australian Ringnecks Barnardius zonarius were the most frequently detected granivorous species (12.7 and 12.1% of all observations, respectively). The abundances of birds along roads were positively correlated to road casualties. Australian Raven and Grey Currawong were the most commonly detected road casualties. Road casualties were dominated by juveniles, particularly in the spring and summer months. The Australian Raven and Wedge-tailed Eagle Aquila audax were the only species detected at carrion. The Grey Currawong did not feed from carrion and it undertook a shift away from the road-habitat during its breeding season. The abundances of the granivorous species Common Bronzewing and Australian Ringneck were strongly and positively correlated with the dehiscence of native Jarrah seed. In contrast, the transportation of 116 510 tonnes of grain (over two years) did not correlate with the abundances of granivorous birds. We conclude that food availability on the road most likely correlated with abundance and road casualties of birds, although more detailed studies on insectivorous birds are required to test this hypothesis.
