Hummingbirds are potentially the most colourful birds in the animal kingdom 鈥� at least, they are from the perspective of the birds themselves. An analysis of 114 species of the small, nectar-supping birds suggests they can collectively produce more than one-third of the colours their eyes can theoretically detect.
Birds in general are renowned for their colours, but exactly how colourful they are is difficult to quantify. One way to measure colourfulness is to consider the theoretical total number of colours birds can detect, and then estimate how many of these colours are produced by the birds鈥� feathers.
A 2011 which took this approach to look at a wide variety of birds found that they typically produce only about 30 per cent of the colours they are able to see.
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at Duke University in North Carolina and her colleagues have performed similar work focusing on 114 different species of hummingbird (Trochilidae family), using specimens stored in collections at Yale University and the American Museum of Natural History. It is the first time an entire group of related birds has been studied in this way.
From their analysis, the team estimates that the hummingbirds can produce 34 per cent of the colours that they are able to see.
Most birds can see more colours than humans because they have extra receptors in their eyes which let them see light in the . Hummingbird feathers can be very purple or blue, which is far rarer in other birds.
The researchers also determined that hummingbirds may be so colourful because of the way that certain cellular structures in their feathers are organised. These pigment-producing organelles are layered in such a way that they interfere with light and produce vibrant colours.
鈥淭his type of structural colouration is fairly unique to hummingbirds because of the shape of these organelles which are unusually disc-shaped and hollow, allowing for the creation of very saturated colours,鈥� Venable says.
The researchers found that the most colourful parts of the hummingbird were the throat and the top of the head. This is probably because these body regions are used the most in social interactions, says Venable. 鈥淗ummingbirds use these colourful patches to show off or when they want to say this is my territory and puff themselves out,鈥� she says.
Venable says it is unclear why hummingbirds would be more colourful than any other type of bird.
鈥淭he discovery that hummingbirds can produce a remarkably broad range of plumage colours is fascinating and thought-provoking,鈥� says at Princeton University, who co-authored the 2011 study on colourfulness.
鈥淗ummingbirds are particularly famous for their elaborate courtship and territorial displays and one potential explanation for these findings is that hummingbirds use these vibrant colours to communicate effectively with potential mates and rivals,鈥� says at the University of Sheffield in the UK.
Communications Biology
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