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

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T1 - Luminance-dependence of spatial vision in budgerigars (Melopsittacus undulatus) and Bourke's parrots (Neopsephotus bourkii).

AU - Lind, Olle

AU - Sunesson, Tony

AU - Mitkus, Mindaugas

AU - Kelber, Almut

PY - 2012

Y1 - 2012

N2 - 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.

AB - 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.

U2 - 10.1007/s00359-011-0689-7

DO - 10.1007/s00359-011-0689-7

M3 - Article

C2 - 22001888

VL - 198

SP - 69

EP - 77

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

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

SN - 1432-1351

ER -