Woodcock’s white feathers put swan and dove in shade
THE bird with the whitest feathers in the world is not a swan, dove or snowy owl but the Eurasian woodcock, scientists have found.
The small brown bird, which has darker stripes and has a long, thin bill, does not immediately appear to have any white elements. But tucked under its tail are white-tipped feathers visible only from beneath during flight or when it chooses to expose them, such as during courting displays.
Jamie Dunning, an ornithologist and PHD candidate at Imperial College London, spent the spring 2020 lockdown pondering why the woodcock has these dazzling white feathers, which stand in stark contrast to the rest of its body.
“Under the microscope these feathers have bizarre extensions to the undersides of the ramus – the middle part of the feather – which we call ‘Venetian blind-like’ because that is what it looks like,” he said. “Like the blinds, they are trying to keep light from passing through the gaps.”
The structure, thought to be unique to woodcocks, increases the reflective surface area and makes the feather tips incredibly bright.
Mr Dunning and his study co-authors had access to a database of super-white feathers, which included 61 different species. “All we did was compare the woodcock feathers to this database of the whitest birds you can think of and it was 31 per cent brighter than the next brightest,” he said.
He believes the reason for their feathers being a third whiter than any other bird is that, unlike the other white birds, woodcocks are nocturnal and have evolved the white tips as a way of communicating visually with each other in the dark environment of a woodland at night
“Woodcocks don’t have the privilege of the sunlight to work with, so they have to have this super-bright signal,” he explained.
“Not only do they hang out at night, but they also hang out in woodland under really dense canopy, so they need to be hoovering up all the light available to them. It makes sense that the signal is more intense than a swan or a snowy owl, for example.”
The reason the white tips are not permanently on display is to enable the birds to hide from predators.
“They are camouflaged to avoid being eaten while they sleep so, unlike a peacock, the woodcock needs to be able to keep its signal hidden and get it out only when needed,” said Mr Dunning.
“It’s all about this trade-off between having a showy ornament and being camouflaged – you can’t really have it both ways.
“It’s a real multi-tool for them, a proper Swiss army knife. It’s almost certainly used to signal to the opposite sex. They also flick their white tail feathers at chicks following them on the forest floor, and they use [the tail] as an aggressive thing.
“They’re using it in loads of different contexts. But ultimately, they choose when to show it and when to hide it.”
The study is published in