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First published online August 8, 2003

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Behavioural investigation of polarisation sensitivity in the Japanese quail (Coturnix coturnix japonica) and the European starling (Sturnus vulgaris)

Verity J. Greenwood^*, Emma L. Smith, Stuart C. Church and Julian C. Partridge

Ecology of Vision Research Laboratory, School of Biological Sciences, University of Bristol

View larger version (111K): [in a new window]   Fig. 1. False colour images of the polarisation stimuli showing that the stimulus types differed in angle of polarisation (A) but not in degree of polarisation (B) or radiant intensity (C). The images on the left-hand side were taken from directly above the stimuli, while the images on the right-hand side were taken at an angle of 45° to the plane of the surface of the stimulus. Within each image, the `different' stimulus is always on the left, and the `same' on the right. Panel A shows that the stimuli in these images had orthogonally orientated polarisation patterns (stimulus on the left) or identically orientated polarisation patterns (stimulus on the right). The axis indicates the angle of polarisation in radians. Panel B shows that the degree of polarisation approached 100%. Here, the axis indicates the degree of polarisation, with 0 being unpolarised and 1 indicating 100% polarisation. Panel C shows that the average reflection of the stimuli was about 50%. At the lower border of each image is a Labsphere stepped greyscale with reflections of 12%, 25%, 50% and 99%. The reflection from the greyscale is unpolarised.

View larger version (17K): [in a new window]   Fig. 2. Diagram of the 25 mmx25 mm control stimuli, showing the `same' (S1–S3) and `different' (D) patterns. Blocks of metal were covered with grey paper (as described fully in the text). S1, S2 and S3 had equal reflection on both halves of the stimuli; stimulus D had different grey levels on each half.

View larger version (11K): [in a new window]   Fig. 3. Diagram of the stimuli blocks used in the polarisation discrimination (see text for dimensions).