Anàlisi poblacional i reproducció del gaig blau (Coracias garrulus) al Parc Natural dels Aiguamolls de l’Empordà

Abstract

Last years, European roller Coracias garrulus has undergone a moderately rapid decline across its global range and if this negative trend persists, the status of this species is likely to become Vulnerable in the IUCN Red List. Understanding the strong link between breeding success and bird conservation, this study aims to evaluate possible correlations between nest-site and landscape characteristics and habitat selection and breeding success in this species. This study has been conduct within the natural reserve “Els Aiguamolls de l’Empordà” (PNAE) where the last years European roller population has been stable up to now. Thirtyfive nest-boxes and three Green Woodpecker Picus viridis holes were analysed with field data collection on several nest-site and landscape characteristics. In addition, the establishment of breeding pairs and those with breeding success were quantified. A comparison to 2014 field database shows evidences of a worrying decreasing trend of European roller breeding pairs within the natural reserve indicating the deterioration and loss of suitable nest-boxes as the main factor. As a consequence, inter and intraspecific competition has been registered and also extremely rare data was collected, a nest-box has probably been parasitized by the European cuckoo Cuculus canorus. When compared to unoccupied nest-boxes, occupied nest-boxes were at a lower height (6,89 1,12 m), mostly oriented east, south and southeast therefore were in warmer nest-box microclimates and mostly had circular entrance holes. Although the foraging habitat selection data has been scarce, interesting data such as flight average distance and frequency during the foraging period for chicks has been collected. In this period flights were normally about 200-300 m long but quite fast (mostly about 3-5 min). The present study has also provided a detailed behavioural description during the nest foraging provisioning that highlight the importance of the hedgerows and riparian forest In the surroundings of the nest to allow the birds to perch and detect their prey. Finally, the results have led to the suggestion of a viable framework of conservation measures for the European roller in the natural reserve (PNAE)