Talk Breeding habitat selection and flight characteristics of a farmland raptor species in response to highway in Western France

For the past 50 years, agro-ecosystems have been undergoing an intensification of farming practises which resulted in an overall diminution of habitat quality; formerly rich, the biodiversity of those habitats has been steeply decreasing with e.g.  ~ 90% of farmland bird specialist species considered as threatened in France. These ecosystems, characterised by a low density of human population, low declivitya nd open habitats, have also been prone to the settlement of infrastructures such as power lines, wind farms or transportation routes. Accurately assessing if and how species respond to such modifications of their environment how farmland birds cope with these structures is indispensable to offer appropriate compensation measures. We propose to determine whether the Montagu’s Harrier Circus pygargus, a medium size raptor that breeds mostly in cereal fields and prey upon small rodents, responds to the presence of two highways (among other infrastructures). More precisely, we aim at assessing whether 1/ the distance to a highway affected the density of nests and 2/ whether highways’ edges were positively selected as hunting grounds or if individuals tended to adjust their flight characteristics when flying over different types of structures . For our first objective, data on the breeding ecology of the species and relevant habitat variables (land use and vole abundance) were collected over 2 study areas cumulating ~ 670 km² (450 and 220 km², between 1997-2015 and 2008-2013 respectively). To investigate the movement ecology of males, 18 individuals were fitted between 2012 and 2015 with light GPS units that allowed us to precisely record their locations and flight characteristics. Analyses conducted on one of the 2 study areas revealed that nests density increases when distance to the highway increases, suggesting that birds avoid the vicinity of highways.  Preliminary analyses on birds’ behaviour suggest that Montagu’s harriers do not use the border of highways as hunting grounds and tend to respond to the presence of highway (or buildings) on their path by increasing their flying altitude. We believe these results, though based on empirical data, will shade new light on the potential effects of highway on a farmland species and will help in implementing efficient mitigation measures in future transportation projects crossing agricultural landscapes.

highway, farmland species, habitat selection, breeding ecology, direct response, avoidance behaviour, attraction,