Ornis Hungarica. vol.7. (1997) p.27-37.
Nesting success of the Red-backed Shrike (Lanius collurio) in a cultivated area
We studied a stable population of Red-backed Shrikes in the Aggtelek National Park on an area which is a mosaic of arable lands with different degrees of cultivation. We analyzed the effect of cultivation on nesting success. We defined three types of land use: intensively cultivated plough-lands, extensively cultivated meadows or pastures, and uncultivated areas. Based on regular observations from several points on a transect, we made a map showing the location of the nests, the territories of the observed pairs and the land types. The observation period lasted 50-55 days a year between 1991 and 1996. We found that the decisive majority of nest failures were caused by predators. The nesting success was higher in the intensively cultivated and uncultivated lands than in the extensively cultivated areas. Bush size also affected nesting success, the risk of nest failure was lower in large groups of bushes than in lonely bushes. Human disturbance may have increased nest failures. We did not find any effect of bush type and distance from forest-edge on nesting success. We neither found any difference between the densities of pairs from different land-use types.