This story is hot off the press. It broke only a few weeks ago. Puffin beaks glow. Before I explain, let me first provide some background. Visible light is the range of electromagnetic waves that our eyes can sense. When all the waves are mixed together, it appears as white light. Prisms break white light into colors. Raindrops break light into rainbows.
There are wavelengths of light outside the visible spectrum. At the lower end is infrared. Ultraviolet is at the higher end, with wavelengths that are shorter than visible light. These colors are invisible to humans, but are within the visible range of some animals. For instance, the Maine state bird can see into the ultraviolet range. To us, male and female chickadees are indistinguishable. But in the ultraviolet range, the genders look surprisingly different. The dark bib is larger on males, and the cheek patches glow brightly white. The males also have grayer backs in UV light.
Owls are particularly fascinating. They are generally colored in shades of brown and black. Most bird colors come from the refraction of light through feathers, or the reflection of light off colorful pigments.
But owls have a very different set of pigments, called porphyrins. These pigments glow in ultraviolet light. The tiny northern saw-whet owl is found all over Maine, assuming you are lucky enough to find it. They are plentiful but secretive. It turns out, recently molted feathers glow more brightly under ultraviolet light. Furthermore, owls molt in a unique pattern.
Most birds molt all their feathers in rapid succession. Some molt more slowly. Owls molt just some feathers, and this varies by the age of the bird. So it is actually possible for biologists to determine the age of an owl they are banding, just by noting which feathers are glowing under UV light.
Even more interesting, rodent urine fluoresces in UV light. Owls can follow the trail of mouse urine and often figure out where the next meal is coming from. Owls need to see in the dark, and their eyes sacrifice the ability to perceive many of the colors that are visible to humans. But they make up for it by coloring themselves in dull-but-unusual pigments and taking advantage of ultraviolet light.
Which brings me back to puffins. Three weeks ago, articles started popping up in my inbox from various sources — including Smithsonian — that the beaks of Atlantic puffins light up under ultraviolet light. Jamie Dunning is an ornithologist affiliated with the University of Nottingham, England. He had long been aware that the bill of a crested auklet, a diminutive relative of the puffin, glows under a blacklight. While examining a dead puffin during a dull day in January, he rather nonchalantly placed it under UV light. The yellow bands on the bill lit up like pearls in moonlight.
You don’t need to remember this, but it’s called tetrachromatic vision. Humans see in three basic colors, where all colors are combinations of red, blue, and green (RBG). RBG is the way inkjet printers reproduce color. Some animals, including puffins, perceive ultraviolet for a fourth color dimension. We don’t know exactly what they see, but we know they see it. Nothing in nature happens by accident.
After breeding season, puffin bills shrink and become less colorful. It’s not rocket science to assume that a colorful shiny bill has something to do with attracting a mate.
All that mate-attraction is just getting started. The biggest puffin colony along the Maine coastline is Machias Seal Island, and the first returning puffins arrived three weeks ago. Puffins spend their entire lives at sea, and only return to nest. After fledging, the young ones don’t touch land again for four to five years. Soon, all the adults will be strutting their stuff and flashing their glow-in- the-dark bills along all five of Maine’s coastal nesting colonies. Maine’s first birding visits to these islands will occur during the Wings, Waves, Woods Festival in Stonington from May 18-20.
Meanwhile, the next scientific step is to test UV light on live puffins. There is a chance that the fluorescence is caused by the decaying process, so that possibility must be ruled out. In order to put a live puffin under ultraviolet light without damaging its eyes, Dunning is designing special sunglasses for the birds in his study. Darn. If I had known I would have the chance to put sunglasses on puffins, I would have been a scientist.
Bob Duchesne serves as vice president of Maine Audubon’s Penobscot Valley Chapter. He developed the Maine Birding Trail, with information at mainebirdingtrail.com. He can be reached at firstname.lastname@example.org.