The effect of flicker from fluorescent lights on mate choice in captive birds

The visual systems of birds are hypothesized to have higher temporal resolution than those of humans, suggesting that they may be able to perceive the flicker emitted from conventional low-frequency fluorescent lights (LF; 100 Hz in Europe, 120 Hz in the U.S.A.). These lights are commonly used in the housing of captive birds and this may affect both their welfare and performance in experiments. We carried out mate choice experiments on European starlings, Sturnus vulgaris, under both low- and high-frequency fluorescent lights (HF; >30 kHz, at which flicker is imperceptible). Indicators of male condition and size, together with the reflectance spectra and length of the males' throat feathers, were also recorded to ascertain which variables correlated with female preference. Females ranked males consistently under HF, but not LF, lighting, and individual females chose different males under the two lighting types. Under HF lighting, females chose to spend more time with males that had longer throat feathers. The flicker rate of the light clearly affected the choices made by the females, possibly because of nonspecific stress effects or decreased discrimination ability. Our results imply that careful interpretation of mate choice experiments is needed, especially with regard to the lighting types used, to elucidate the real cause behind any variation shown.