Innate and learned aspects of vole urine UV-reflectance use in the hunting behaviour of the kestrel (_Falco tinnunculus_)

Some birds are known to use the UV reflectance in their feeding strategy. Knowing that the common kestrel Falco tinnunculus is able to recognise vole trails by perceiving the UV reflectance of their scent marks, this study was designed to investigate whether the use of scent marks in the UV range has an innate component, or if it is only acquired with experience. We tested the preference of 44 experienced adult and 49 naïve juvenile common kestrels in four types of arenas: (1) scent-marked and covered with a UV transmitting filter (UV+SC), (2) scent-marked and covered with a UV blocking filter (UV-SC), (3) sprinkled with water and covered with a UV transmitting filter (UV+W), and (4) sprinkled with water and covered with a UV blocking filter (UV-W). We assessed the birds’ preference by counting the number of visual scans and visits to each arena. The distribution of scans differed from random in both adults and juveniles. The birds scanned the UV+SC arena more often than the others. Since naïve individuals showed the same preference as experienced ones, we hypothesised that the association between vole scent UV reflectance and vole presence has an innate component in the common kestrel. Nevertheless, adults differed from juveniles because they perceived the scented arenas from the water sprinkled ones, in fact, adults scanned the UV-SC arena more frequently than both UV+W and UV-W arenas. This result suggests that the ability of detecting UV cues has a learned component.