Behavioural and physiological effects of absence of ultraviolet wavelengths on European starlings Sturnus vulgaris

As ultraviolet wavelengths are used in normal avian colour perception, the maintenance of captive birds under artificial lighting (which is normally UV-deficient) may have welfare implications. European starling Sturnus vulgaris juveniles kept in UV-deficient light environments had significantly higher basal plasma corticosterone concentrations than those kept under full spectrum lighting, in the second of two experimental blocks. UV-deficient conditions also led to significant changes in behaviour indicative of escape (less perching and more hanging on the cage and pecking at it). However, the birds from the first block, where the interval between transfer to the experimental set-up from the wild was short (2 days), showed significantly higher basal and maximum plasma corticosterone concentrations than those in the second block and no additional effect of light environment on either corticosterone or behaviour. We hypothesise that this difference between blocks was due to the overriding initial stress of being in captivity swamping any treatment effects. Capture stress had declined in the second set of birds, which entered the experiment after 7-14 days in captivity. Stress effects of UV-deficient lighting appear small relative to the overall impact of captivity, but may nevertheless become apparent after the initial effects of capture subside.