Effect of implementation of irrigation on raptor and corvid populations in a Mediterranean agrosystem

• Published in: Animal Biodiversity and Conservation
• Main Authors: Villanúa, D., Cabodevilla, Xabier, Ardaiz, J., Lizarraga, A., Zufiaurre, A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Museu de Ciències Naturals de Barcelona 2023
• Subjects: Agriculture-intensification; Census; Harrier; Steppe; Circus cyaneus; Aquila chrysaetos; golden eagle
• Online Access: https://doi.org/10.32800/abc.2023.46.0155; https://repositori.udl.cat/handle/10459.1/463967

We analyzed changes in the composition of the community of birds of prey and corvids in a rainfed agrosystem after the transformation of 37.2 % of the sampled area into irrigated land between 2005 and 2020. We sampled 57 transects (372 km per year) and fitted generalized linear mixed models (GLMM) to study changes in species occurrence. Our results showed that specific richness and the Shannon index did not vary significantly between rainfed and irrigated transects, but there was a certain positive trend when comparing the years 2005 and 2020. Regarding the differences detected for each species, the occurrence of Montagu’s harrier Circus pygargus, hen harrier Circus cyaneus, Eurasian short-toed eagle Circaetus gallicus, griffon vulture Gyps fulvus and carrion crow Corvus corone was significantly lower in irrigated land than in rainfed land, while magpie Pica pica, Western marsh harrier Circus aeruginosus, common kestrel Falco tinnunculus and black kite Milvus migrans showed a significantly higher occurrence in the irrigated transects. In addition, our findings confirm a significant decrease in occurrence between 2005 and 2020 both in rainfed and irrigated areas for Montagu’s harrier, hen harrier and magpie, while Western marsh harrier, golden eagle Aquila chrysaetos, common buzzard Buteo buteo, red kite Milvus milvus, griffon vulture Gyps fulvus, red-billed chough Pyrrhocorax pyrrhocorax and Western jackdaw Coloeus monedula were detected significantly more frequently in 2020 than in 2005. These results suggest that assessment of the impact of a new irrigation system should focus on the most characteristic species of rainfed agrosystems because the apparently positive effect on other species, equally protected but more generalist, may mask the real effect on conservation. Both the field work, the data analysis and writing of the manuscript were carried out without any type of financial support