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The intensity threshold of colour vision in two species of parrot

Lind, Olle LU and Kelber, Almut LU (2009) In Journal of Experimental Biology 212(22). p.3693-3699
Abstract
We have used behavioural tests to determine the intensity thresholds of colour vision in Bourke's parrots (Neopsephotus bourkii) and budgerigars (Melopsittacus undulatus). We have also examined the relationship between these thresholds and the optical sensitivities of single photoreceptors using morphological methods. Bourke's parrots lose colour vision in brighter light (0.4 cd m(-2)) than budgerigars (0.1 cd m(-2)) and both birds lose colour vision in brighter light ('end of civil twilight') than humans (0.02 cd m(-2),. moonlight'). The optical sensitivities of single cones are similar in both birds (budgerigar 0.27 mu m(2) sr, Bourke's parrot 0.25 mu m(2)sr) but Bourke's parrots have more (cone to rod ratio, 1.2:1.0), thinner (2.8 mu m)... (More)
We have used behavioural tests to determine the intensity thresholds of colour vision in Bourke's parrots (Neopsephotus bourkii) and budgerigars (Melopsittacus undulatus). We have also examined the relationship between these thresholds and the optical sensitivities of single photoreceptors using morphological methods. Bourke's parrots lose colour vision in brighter light (0.4 cd m(-2)) than budgerigars (0.1 cd m(-2)) and both birds lose colour vision in brighter light ('end of civil twilight') than humans (0.02 cd m(-2),. moonlight'). The optical sensitivities of single cones are similar in both birds (budgerigar 0.27 mu m(2) sr, Bourke's parrot 0.25 mu m(2)sr) but Bourke's parrots have more (cone to rod ratio, 1.2:1.0), thinner (2.8 mu m) and longer rods (18.5 mu m) than budgerigars (2.1:1.0, 3.4 mu m, 13.3 mu m). Bourke's parrots thus have an eye type that, with a flexible pooling mechanism, allows for high resolution or high absolute sensitivity depending on the light conditions. The results nicely agree with the activity patterns of the birds, Bourke's parrots being active during the day and in twilight while budgerigars are not normally active before sunrise and after sunset. However, Bourke's parrots have fewer cones than budgerigars, which implies that a smaller number of cones are pooled within each retinal integration area. That could explain why Bourke's parrots have a higher intensity threshold of colour vision than budgerigars. Furthermore, the study emphasises the need to expand the sensitivity measure so that photoreceptor integration units are used rather than single receptors. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
optical sensitivity, behavioural experiments, bird, colour vision, schematic eye, threshold
in
Journal of Experimental Biology
volume
212
issue
22
pages
3693 - 3699
publisher
The Company of Biologists Ltd
external identifiers
  • wos:000271383100018
  • scopus:70449914557
ISSN
1477-9145
DOI
10.1242/jeb.035477
language
English
LU publication?
yes
id
1c120c4e-17d6-4a9b-90e9-4950488d9338 (old id 1505000)
date added to LUP
2009-11-24 17:06:56
date last changed
2017-06-18 03:32:33
@article{1c120c4e-17d6-4a9b-90e9-4950488d9338,
  abstract     = {We have used behavioural tests to determine the intensity thresholds of colour vision in Bourke's parrots (Neopsephotus bourkii) and budgerigars (Melopsittacus undulatus). We have also examined the relationship between these thresholds and the optical sensitivities of single photoreceptors using morphological methods. Bourke's parrots lose colour vision in brighter light (0.4 cd m(-2)) than budgerigars (0.1 cd m(-2)) and both birds lose colour vision in brighter light ('end of civil twilight') than humans (0.02 cd m(-2),. moonlight'). The optical sensitivities of single cones are similar in both birds (budgerigar 0.27 mu m(2) sr, Bourke's parrot 0.25 mu m(2)sr) but Bourke's parrots have more (cone to rod ratio, 1.2:1.0), thinner (2.8 mu m) and longer rods (18.5 mu m) than budgerigars (2.1:1.0, 3.4 mu m, 13.3 mu m). Bourke's parrots thus have an eye type that, with a flexible pooling mechanism, allows for high resolution or high absolute sensitivity depending on the light conditions. The results nicely agree with the activity patterns of the birds, Bourke's parrots being active during the day and in twilight while budgerigars are not normally active before sunrise and after sunset. However, Bourke's parrots have fewer cones than budgerigars, which implies that a smaller number of cones are pooled within each retinal integration area. That could explain why Bourke's parrots have a higher intensity threshold of colour vision than budgerigars. Furthermore, the study emphasises the need to expand the sensitivity measure so that photoreceptor integration units are used rather than single receptors.},
  author       = {Lind, Olle and Kelber, Almut},
  issn         = {1477-9145},
  keyword      = {optical sensitivity,behavioural experiments,bird,colour vision,schematic eye,threshold},
  language     = {eng},
  number       = {22},
  pages        = {3693--3699},
  publisher    = {The Company of Biologists Ltd},
  series       = {Journal of Experimental Biology},
  title        = {The intensity threshold of colour vision in two species of parrot},
  url          = {http://dx.doi.org/10.1242/jeb.035477},
  volume       = {212},
  year         = {2009},
}