Puffin is arguably the most recognisable, charismatic and attractive of all North Atlantic seabirds, with the species' brightly coloured beak and clown-like expression making it a favourite with birders and non-birders alike.
That& beak is a hugely important feature in Puffin social life. When pairing up for the breeding season, females are attracted to males with the biggest and most colourful bills. Not only does brightness suggest good health, but a bigger size indicates an older male, who may be more experienced (and thus successful) at rearing chicks.
The species' display focuses on the beak: pairs will approach each other, excitedly bobbing their heads, before rubbing their beaks together in a courtship known as 'billing'.
And now newly published research from The University of Nottingham suggests that the importance of the beak is greater than previously thought.
Working with scientists in the United States and Canada, the research team has become the first to demonstrate photoluminescence in Puffins' beaks – meaning that they effectively glow under ultraviolet (UV) light.
The 'glow' of a Puffin's bill under UV light (Jamie Dunning).
The phenomenon was first observed in dead Puffins, all of which had died of natural causes, then recreated in tests on live birds in the United States.
Jamie Dunning, who was undertaking research at Nottingham's School of Life Sciences for his Master's degree when he made the discovery, commented: "At this stage, we aren't really sure why Puffins need this trait. However, we expect that they can detect it and we suspect that it is linked to sexual signalling, feeding young in their burrows or perhaps even capturing prey. We will be working on these questions in the future."
Photoluminescence works when a substance produces light after excitation from a light source in a different wavelength, in this case from ultraviolet or infrared light.
The scientists first noted photoluminescence in Puffins in February 2017 in a lab at the University of Nottingham. Each bird was photographed under black light to document the presence and location of the glowing areas of the beak.
Last year, they recreated the experiment using three live Puffins caught on Petit Manan Island in Maine, USA, which is owned and managed by the US Fish and Wildlife Service.
The test posed a tricky ethical dilemma as shining UV light into the birds' eyes could potentially cause damage. To protect the Puffins, scientists worked with the Interaction Research Studio at Goldsmiths, University of London, to develop a specially shaped opaque eye shield made from foam and waterproof neoprene – in simpler terms, 'Puffin sunglasses'.
'Puffin sunglasses' were used to protect the birds from potentially harmful UV light (Dean Brown).
Photoluminescence serves a number of functions in nature, such as deterring predators, luring underwater prey and enhancing signals during mating.
As the glowing regions on the bill are developed during the breeding season and shed over winter, the scientists believe that the property could play a role in the courtship rituals of the birds. Potentially, the glow could also help chicks to locate their parent's beak – and the food they are bringing – in the low light conditions of the underground burrows.
However, they don't yet know whether Puffins are able to see the UV light at all and further study is needed into the links between these photoluminescent properties and behaviour and ecology in the auk family.
Dunning, J, Diamond, A W, Christmas, S E, et al. 2019. Photoluminescence in the bill of the Atlantic Puffin Fratercula arctica. Bird Study vol 65, no 4, pp 570-573. DOI: https://doi.org/10.1080/00063657.2018.1563771