No response to linear polarization cues in operant conditioning experiments with zebra finches.

Many animals can use the polarization of light in various behavioural contexts. Birds are well known to use information from the skylight polarization pattern for orientation and compass calibration. Still, there are few controlled studies of polarization vision in birds, and the majority of them have not been successful in convincingly demonstrating polarization vision. We used a two-alternative forced choice conditioning approach to assess linear polarization vision in male zebra finches in the "visible" spectral range (wavelengths>400 nm). The birds were trained to discriminate colour, brightness, and polarization stimuli presented on either one of two LCD-screens. All birds were able to discriminate the colour and brightness stimuli, but they were unable to discriminate the polarization stimuli. Our results suggest that in the behavioural context studied here, zebra finches are not able to discriminate polarized light stimuli.