In a new study, researchers have found that a group of parrots in the wild sleep with their eyes closed for a day, as part of a long-term, synchronized practice of using their eyes to see.
In the wild, this practice of eyes-open-close is called parrot sleep, or eye-sleep.
However, scientists at the University of New South Wales in Australia have shown that it has the opposite effect.
The researchers found that, when compared with other birds, the parrots that were trained to use their eyes during this long-duration eye-sitting practice experienced significant changes in their eye movements, and the rate at which they moved their eyes was also altered.
These changes were most noticeable when the birds were allowed to watch videos of people with whom they interacted.
When the researchers were able to control for the number of videos that the birds watched, they found that the parrot that was trained to stay awake during the eye-opening period experienced a significant increase in eye movements when it was allowed to view its partner.
The same birds that had learned to keep their eyes open during the practice also had a significant decrease in eye movement when allowed to look at a video.
The results of the study, published today in Proceedings of the Royal Society B, are consistent with previous research showing that parrots do not require eyes to perform eye-switching tasks, and that this ability to change eye movements is a core component of the long-lasting, synchronized nature of the practice.
“We found that parrot eyes open and close with an increase in their activity during eye-waving, and they do not show this activity during a full eye-scan,” says Dr. Andrew Kowalczyk, who led the study.
“It is possible that the change in eye-movement we saw was due to a change in the shape of the paralysed eye.
This could mean that the bird is using its eyes to read the world around it, or that the eye is moving to avoid predators.”
Kowalecki’s co-author, Dr. Michael Kueppers, is a PhD student in the Department of Biological Sciences at the Royal Australian and New Zealand College of Veterinary Surgeons, and he is also a co-first author on the study paper.
The new research, which focuses on how parrots perceive the world, could help explain the remarkable degree of social organization and communication that is required to maintain this social network in a species that is not fully social, the authors note.
The study was funded by the National Science Foundation, the National Institutes of Health, the Natural Environment Research Council of Australia, the Australian Science Foundation and the Australian Research Council.