Roost selection flexibility of European starlings aids invasion of urban landscape

The ability to shift habitat preferences is one of the characteristics of flexibility in a species and can be a key to the success of invasive species. Our objective in this paper was to analyse the possible behavioural flexibility of European starling (Sturnus vulgaris) through its rapid adjustment to changes in roost site availability. First we analysed the change of starling roost sites at regional (Brittany, 1973–1997, 87 sites) and at town scales (Rennes, 1983–2004, 59 sites) in western France. Site selection followed changes in habitat availability, switching from reed beds to conifer plantations regionally, and from hedges/bushes to trees, especially conifers, in Rennes. Secondly, we analysed urban roost sites measuring several characteristics of trees and neighbouring environment. Roost trees were taller and had a bole circumference and canopy larger than non-roost trees. Trees with a large amount of small branches were more selected by starlings. Among environmental features including landscape composition and configuration, only temperature was higher in roost sites. Starlings show great flexibility in choice of roost site characteristics which may in part explain their success as an invasive species and as urban colonists. Despite such flexibility, preferred roost site characteristics could be used to reduce urban nuisance by managing/creating sites in less sensitive locations.