Seasonal variation in isotopic composition of blood of Nyctalus lasiopterus.
Means±SE for δ13C (purple circles) and δ15N (orange squares) for each sampling event are given. Numbers at the top of the figure designate sample size. The black line indicates nocturnal migration density of small passerines tracked by radar in southern Spain . The shaded area represents proportion of feathers found in faecal pellets of Nyctalus lasiopterus.