The dark ‘eyeliner’ feathers of peregrine falcons act as sunscreens to enhance the birds’ hunting ability, a new scientific study suggests.
Scientists have long speculated that hawk eye markings enhance their ability to target fast-moving prey, such as pigeons and pigeons, in sunlight.
Now research suggests that these brands have evolved based on the weather; the sunnier the bird habitat, the larger and darker the telltale dark ‘sun shade’ feathers are.
The distinctive dark stripes directly below the peregrine falcon’s eyes, called the malar stripe or ‘mustache’, likely reduce glare from sunlight and confer a competitive advantage during high-speed chases. It’s an evolutionary trait mimicked by some elite athletes who apply dark makeup under their eyes to help them spot fast-moving balls in competitive sports.
Until now, there have been no scientific studies linking solar radiation levels to the dark plumage of the ‘eyeliner’, which is common to many other species of falcons.
The scientists used photos of peregrine falcons from around the world posted on the web by bird watchers and rated the size of each bird’s malar stripe.
They then explored how these malar strips varied in relation to aspects of the local climate, such as temperature, rainfall, and the strength of sunlight.
The study, published in the journal Biology lettering, was conducted by researchers from the University of Cape Town (UCT) and the University of the Witwatersrand in South Africa.
It involved comparing the characteristics of the malar strip, including width and prominence, of individual peregrine falcons, using more than 2,000 photographs of pilgrims stored in online citizen science libraries.
The researchers examined samples from 94 different regions or countries. The results showed that the peregrine falcon’s malar stripes were larger and darker in regions of the world where sunlight is strongest.
“The sunburst hypothesis has become entrenched in popular literature, but it has never been empirically tested before,” said Michelle Vrettos, a UCT master’s student who conducted the research.
Vrettos added: “Our results suggest that the function of the malar fringe in pilgrims is best explained by this hypothesis of solar glare.”
Associate Professor Arjun Amar from UCT’s FitzPatrick Institute, who supervised the research, said: “The peregrine falcon represents the ideal species to explore this long-standing hypothesis, because it has one of the most widespread distributions of all bird species, being present in all the continents except Antarctica; therefore, it is 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 investigation would not have been possible. “
Source: University of Cape Town