The browser you are using is not supported by this website. All versions of Internet Explorer are no longer supported, either by us or Microsoft (read more here: https://www.microsoft.com/en-us/microsoft-365/windows/end-of-ie-support).

Please use a modern browser to fully experience our website, such as the newest versions of Edge, Chrome, Firefox or Safari etc.

The intensity threshold of colour vision in two species of parrot

På svenska

Author

Summary, in English

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.

Publishing year

2009

Language

English

Pages

3693-3699

Publication/Series

Journal of Experimental Biology

Volume

212

Issue

22

Document type

Journal article

Publisher

The Company of Biologists Ltd

Topic

  • Zoology

Keywords

  • optical sensitivity
  • behavioural experiments
  • bird
  • colour vision
  • schematic eye
  • threshold

Status

Published

Research group

  • Lund Vision Group

ISBN/ISSN/Other

  • ISSN: 1477-9145