Falcons have natural ‘eye makeup’ that improves their focus

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Is THIS why falcons are such good hunters? Birds have natural ‘eye makeup’ that improves their ability to target fast-moving prey in bright sunlight, study finds

  • Peregrine falcons are the world’s fastest bird, capable of reaching speeds of 200 mph
  • They have dark spots of feathers under their eyes on an otherwise white face
  • Researchers believe these stripes are used to protect their eyes from sunlight
  • Birds in warmer areas with more sunlight had darker and thicker eye patches

Falcons have natural “eye makeup” that improves their ability to target fast-moving prey even in bright sunlight, a new study reveals.

Using photos of peregrine falcons from around the world, shared by bird watchers, the University of Cape Town team scored the size of dark eye strips on each bird.

These dark markings evolved depending on climate, the team explained, adding that the sunnier the habitat, the larger and darker the “sunshade” feathers.

Known as ‘Eyeliner feathers’, or the malar stripe, are found under the eyes of falcons and authors say they act as a sunscreen to reduce glare from the sun.

The dark malar stripe directly under the peregrine falcon's eyes (left) likely reduces sunlight glare, an evolutionary trait mimicked by some athletes like Tom Brady (right) who smear dark makeup under their eyes to help them recognize fast moving balls in competitive sports

The dark malar stripe directly under the peregrine falcon’s eyes (left) likely reduces sunlight glare, an evolutionary trait mimicked by some athletes like Tom Brady (right) who smear dark makeup under their eyes to help them recognize fast moving balls in competitive sports

Using photos of peregrine falcons from around the world, shared by bird watchers, the University of Cape Town team scored the size of dark eye strips on each bird.

Using photos of peregrine falcons from around the world, shared by bird watchers, the University of Cape Town team scored the size of dark eye strips on each bird.

Peregrine Falcons

The peregrine falcon (Falco peregrinus) has a wide distribution and inhabits every continent of the world except Antarctica.

They are large and powerful, with a wingspan of up to 115 cm and a weight of up to 1,300 g. They have long broad and pointed wings with a rather short tail and a black ‘mustache’ which contrasts with their white faces.

It is known for its speed, being able to reach up to 200 miles per hour during a characteristic high speed dive as it hunts its prey.

It is the fastest bird in the world and the fastest member of the animal kingdom, with some birds reaching 242 miles per hour.

They are of Least Concern on the IUCN conservation list, with breeding areas spanning Arctic tundra and tropical environments, making it the most common bird of prey in the world.

Its diet consists of medium-sized birds, but can also feast on small mammals, small reptiles and even insects in times of scarcity. They mate for life and normally nest on cliffs or tall man-made structures.

This streak of dark feathers under the eyes of many falcon species has long left scientists speculating as to whether it’s there to improve the ability to aim.

Other birds, such as doves and doves, can hunt fast-moving prey in bright sunlight, and the authors suspected the streak allowed falcons to do the same.

“It’s an evolutionary trait mimicked by some athletes who put dark makeup under their eyes to help them spot fast-moving balls in competitive sports,” they said.

This is the first study to examine levels of solar radiation around the world to the size of the dark ‘eyeliner’ plumage common in falcons.

To discover how universal the eyeliner is and how it varies with climate, the researchers had to watch falcons in different locations.

Bird watchers gave the authors access to a wealth of images from around the world, allowing them to score the size of the malar stripe for each bird.

The team then examined how these streaks varied in relation to the local climate — including average rainfall, temperature and the strength of sunlight.

They had access to 2,000 photos of peregrine falcons stored in citizen science libraries that also clearly showed the bird’s stripe size and location, and compared characteristics such as stripe width and prominence.

These images came from 94 different regions or countries and show that the malar stripes were larger and darker in areas with more sunlight.

“The solar glare hypothesis is ingrained in the popular literature, but it has never been tested empirically before,” said study author Michelle Vrettos.

This streak of dark feathers under the eyes of many falcon species has long left scientists speculating as to whether it's there to enhance target ability

This streak of dark feathers under the eyes of many falcon species has long left scientists speculating as to whether it’s there to enhance target ability

Known as 'eyeliner feathers', or the malar stripe, they are found under the eyes of falcons and authors say they act as a sunscreen to reduce glare from the sun

Known as ‘eyeliner feathers’, or the malar stripe, they are found under the eyes of falcons and authors say they act as a sunscreen to reduce glare from the sun

“Our results suggest that the function of the malar stripe in peregrine falcons is best explained by this solar glare hypothesis.”

Associate professor Arjun Amar, who led the study, said peregrine falcons are the ideal species to explore this long-standing hypothesis.

“It has one of the most widespread ranges of any bird species and is present on every continent except Antarctica – it is therefore exposed to some of the brightest and some of the dullest areas in the world.”

Amar added: ‘We are grateful to all the photographers around the world who have posted their photos on websites. Without their efforts this research would not have been possible.’

The findings are published in the journal Biology Letters.

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