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Luminance-dependence of spatial vision in budgerigars (Melopsittacus undulatus) and Bourke's parrots (Neopsephotus bourkii).

Author

Summary, in English

Budgerigars (Melopsittacus undulatus) and Bourke's parrots (Neopsephotus bourkii) are closely related birds with different activity patterns. Budgerigars are strictly diurnal while Bourke's parrots are active in dim twilight. Earlier studies show that the intensity threshold of colour vision is similar in both species while Bourke's parrots have larger eyes with a higher density of rods than budgerigars. In this study, we investigate whether this could be an adaptation for better spatial vision in dim light. We used two alternative forced-choice experiments to determine the spatial acuity of both species at light intensities ranging from 0.08 to 73 cd/m(2). We also determined the spatial contrast sensitivity function (CSF) for bright light in Bourke's parrots and compare it to existing data for budgerigars. The spatial acuity of Bourke's parrots was found to be similar to that of budgerigars at all light levels. Also the CSF of Bourke's parrots is similar to that of budgerigars with a sensitivity peak located between 2.1 and 2.6 cycles/degree. Our findings do not support the hypothesis that Bourke's parrots have superior spatial acuity in dim light compared to budgerigars and the adaptive value of the relatively rod-rich and large eyes of Bourke's parrots remains unclear.

Publishing year

2012

Language

English

Pages

69-77

Publication/Series

Journal of Comparative Physiology A: Neuroethology, Sensory, Neural, and Behavioral Physiology

Volume

198

Document type

Journal article

Publisher

Springer

Topic

  • Zoology

Status

Published

Research group

  • Lund Vision Group

ISBN/ISSN/Other

  • ISSN: 1432-1351