Farming practices and Roller Coracias garrulus conservation in south-west Spain

There are no previous studies supporting the link between the decline of Roller Coracias garrulus populations in the Palaearctic and agricultural intensification. We studied the effect of farming practices on Roller reproduction during 1988-1991 in south-west Spain. Nest-boxes were installed on power pylons that crossed six different man-made habitats representing the most characteristic habitats in the Mediterranean region: pasture fields with and without holm oak Quercus roffindifolia trees, cereal fields with and without holm oak trees, scrub fields and irrigated fields. Rollers nesting in nest-boxes erected in unwooded pasture field had the highest breeding success, suggesting that this is the most suitable nesting habitat of Rollers in the region. There were no significant effects of farming practices in habitat adjacent to nests on Roller laying date and clutch size. However, after controlling for laying date, current agricultural practices around nests affected chick mortality, with higher losses in irrigated fields. Breeding success and egg productivity were also affected by farming activities, with the lowest values in irrigated fields. Future conservation plans for Rollers should consider that nest-box provision might increase habitat suitability for Roller reproduction and that highly intensified agricultural practices might have deleterious effects on Roller populations.