The most attractive male birds attract more females and as a result are most successful in terms of reproduction. This is the starting point of many studies looking for factors that influence sexual selection in birds. However, is it reasonable to assume that birds see what we see? In a study published in the latest issue of American Naturalist, Uppsala researchers show that our human vision is not an adequate instrument.
“The results mean that many studies on sexual selection may need to be re-evaluated,” says Anders Odeen, research assistant at the Department of Animal Ecology at Uppsala University, who carried out this study with his colleague Olle Håstad.
The significance of birds’ plumage, both in terms of richness of colour and particular signals, has been shown to be a major factor in birds’ choice of partner. In order to assess the colours of birds, everything from binoculars to RGB image analyses are used. However, most studies are based on the hypothesis that human colour vision can be used to assess what birds see.
“It’s a bit like a colour blind person describing the colours of clothes – it’s often quite accurate but sometimes it can go badly wrong.”
This problem has been discussed in the research arena, but so far no study has been able to show its extent. The Uppsala researchers used a mathematical model to investigate how bird and human retina work. Using the model combined with information on differences in the colour-sensitive cones of the eye, they have been able to figure out how colour contrasts are perceived. Greater colour contrast can be translated as ‘richness of colour’ or more ‘brightly coloured’.
“We show that the colours are perceived differently in over 39 percent of cases, which means that it is possible that more than one third of previous studies have been based on inaccurate information.´
The differences were partly due to the fact that human vision cannot perceive UV light, while avian vision can. There are several differences between human and avian perception of colour, which show that certain shades that can be seen clearly by birds are not perceived at all by humans. Through evolution, our colour vision has developed from a more primitive version. This means that we have gone from having two types of colour sensitive cones in our eyes to having three. Birds have four.
“Most other animal species only have two, which means that their colour vision is rudimentary. It is human colour vision that differs from the norm, so in reality it’s ridiculous to use our colour vision to assess the colours of other animals.
The results are not only significant for basic research on sexual selection. They also illustrate the risks of making certain decisions on the basis of human vision, for example, in designing and legislating on lighting systems for domestic fowl.
Source: Uppsala University
Related stories:
Control your TV simply by waving your arm
(PhysOrg.com) -- Consumers will soon be able to control their TV screens or home entertainment systems simply by waving their hand, thanks to technology developed by Toshiba's Cambridge Research Laboratory in collaboration with the Department of Engineering at the University of Cambridge.
Robotic minds think alike?
Most schoolchildren struggle to learn geometry, but they are still able to catch a ball without first calculating its parabola. Why should robots be any different? A team of European researchers have developed an artificial cognitive system that learns from experience and observation rather than relying on predefined rules and models.
Color sudoku puzzle demonstrates new vision for computing
Researchers at the University of Warwick’s Department of Computer Science have developed a colour based Sudoku Puzzle that will help Sudoku players solve traditional Sudoku puzzles but also helps demonstrate the potential benefits of a radical new vision for computing.
Color is in the eye of the beholder
In some regions of Central Europe, salad dressing is made preferably with pumpkin seed oil, which has a strong characteristic nutty flavor and striking color properties. Indeed, in a bottle it appears red, but it looks green in a salad dressing or mixed with yoghurt.
Fruit Bats are not 'Blind as a Bat'
The retinas of most mammals contain two types of photoreceptor cells, the cones for daylight vision and colour vision, and the more sensitive rods for night vision. Nocturnal bats were traditionally believed to possess only rods. Now scientists at the Max Planck Institute for Brain Research in Frankfurt and at The Field Museum for Natural History in Chicago have discovered that nocturnal fruit bats (flying foxes) possess cones in addition to rods. Hence, fruit bats are also equipped for daylight vision.
Why Popeye only has eyes for spinach
Eating spinach could protect your eyes from the leading cause of blindness in western society, say experts at The University of Manchester.
South African Large Telescope Makes Its Debut
Exactly five years after groundbreaking, the Southern African Large Telescope (SALT) project has released its first colour images, marking the achievement of 'first light' and the successful debut of full operation for SALTICAM, a $600 000 digital camera designed and built for SALT at the South African Astronomical Observatory (SAAO). SALT is the largest optical telescope in the southern hemisphere, and equal to the largest in the world. Gathering more than 25 times as much light as any existing African telescope, SALT can detect objects as faint as a candle flame on the moon.
Driving improvements to night vision
In a bid to reduce the annual death of more than 50,000 people and the countless severe injuries on Europe’s roads, future onboard night vision systems have been developed that highlight unexpected obstacles and improve driver visibility.