Anders Ödeen is Assistant Professor at the Department of Animal Ecology, Uppsala University. He is not a bird watcher, but since he studied the many species of yellow wagtails he has become increasingly interested in birds. That birds can see in the ultraviolet has been a revelation to him.
- I realised then that there is a large field of research which still has many gaps in knowledge. My research colleagues and I want to find how colour vision affects birds and their relationship with humans, says Anders Ödeen.
Advanced vision
Birds have a much more advanced colour vision than humans. We have three kinds of rods in the eye, and can, according to trichromatic colour theory, perceive the primary colours red, green and blue. Avian vision is called tetrachromatic since they have four kinds of rods (out of five) which are considered to be involved in colour vision. They can see more colours and also ultraviolet light, and they can update visual impressions faster than we can.
This ought to have effects on artificial lighting for birds in captivity, thought Ödeen and zoologist Olle Håstad, and they turned to the Department of Animal Nutrition and Management at Swedish University of Agricultural Sciences SLU. Researchers Lotta Wallenstedt and Ragnar Tauson there could tell them more about chicken behaviour.
- They confirmed that birds become stressed by the wrong kind of light, says Anders Ödeen. Humans and pigs feel well in daylight, while domesticated chickens can be very sensitive to strong light of the wrong character. The reason is that chickens are fundamentally quite photophobic animals. The original species, the junglefowl, prefers to avoid open places. It generally lives in the undergrowth where light is filtered through the foliage.
The researchers are investigating two kinds of chickens – Bovan White and the old Swedish bantam chicken. Anders Ödeen says that the latter behaves in practically the same way as the junglefowl, and is much more sensitive to flashing than the white chicken.
- Something has changed in the white chicken when they were bred for better laying properties, he says.
Important foods. During their lives chickens must have good conditions. Unsuitable lighting can stress chickens. – To have better control over such disturbances, artificial light ought to be adapted to the chickens' eyes, considers Anders Ödeen, Assistant Professor at the Department of Animal Ecology, Centre of Evolutionary Biology, Uppsala University. Photographer: Diana Rubene
Daylight disturbs
If chickens have too much daylight, this can create disturbances in a population. Anders Ödeen cites some examples:
- Stressed chickens may start to peck at each other's feathers, pull at each other's combs and develop other forms of cannibalism.
The wrong kind of light may even give rise to disturbances in a population, and Anders Ödeen and colleagues have begun to study what the birds' retinas perceive intentionally and unintentionally.
In current experiments, chickens have to peck at panels with rapidly flashing lights. The next step is to compare the birds' reactions in behavioural experiments with the reactions of the retina in ERG, electroretinography, by illuminating the retinas of dead animals.
- This gives an indication of how much of the signals from the retina reach the animal's consciousness - we can say that we find out how much of the flash sensitivity is subliminal, adds Anders Ödeen.
The researchers will also make use of ERG to determine how sensitive the rods in the birds' eyes are to different wavelengths of light. These experiments are conducted by Diana Rubene and Tom Lisney.
- We are testing both flash sensitivity and colour vision, rod by rod, and one colour at a time.
Collisions with planes
When Anders Ödeen is thinking about the usefulness of knowledge of the way birds perceive colours, he particularly focuses on how birds collide with planes and buildings. After discussions with the Swedish Civil Aviation Administration, he realised that such collisions are the largest single cause of air accidents.
- Collisions are dangerous for both the birds and people, and they cost a lot of money. Use could be made here of the differences in avian and human colour vision, and frighten birds away from airfields by, for example, painting and lighting buildings and planes in a certain special way, he says.
Research is conducted into avian vision and behaviour at other universities, both in Sweden and the UK, Chile and Australia. Anders Ödeen nevertheless remarks that it is a pity so few researchers are interested in this subject.
- Vision is the most important sense of a bird. It is not certain that birds perceive natural colourless light, or light that is not flashing, in the same way as we do. We will shortly start a study to determine how dark it can become before chickens lose their ability to see colours.