Richard Collins: Valuable information from trackers on puffin legs
Picture: Sam Langlois Lopez
Thomas Nagel’s celebrated essay, What Is It Like to be a Bat, appeared in the Philosophical Review in 1974. What’s it like to be a puffin is an even more intriguing question.
As a sea-parrot chick, you would first see the light of day from inside a burrow on a steep grassy slope overlooking the sea. An only child, with only the odd rabbit for company, your devoted parents feed you juicy sprats and sand-eels for six weeks. Then, one day, they fail to show up. Distraught, you peer in vain from the mouth of the burrow but, alas, you will never see your folks again. You are on your own. The pangs of hunger force you to take the plunge on your wobbly wings and crash down into the sea, a leap into the unknown. It’s ‘sink or swim’ from then on.
Manx shearwater chicks suffer a similar fate, but guillemot parents are kinder.
Their baby begins life on a narrow ledge high above the rolling waves. One evening at dusk, the father coaxes his three-week-old chick into jumping from the cliff. The youngster, one third-grown ‘unformed, unfinished, scarce half made-up’ à la , falls tumbling and bouncing down the rock-face, on little bastard wings to reach, if it’s lucky, the cruel sea ['Bastard wings' are the tuft of feathers borne by the bony thumb-like structure in a bird's wing, aka alula].
Great black-backed gulls are waiting to pounce, but if you manage to reach the water, you swim with Daddy to comparative safety in the deep ocean. It will be four years before you return to land.
Seabird life-expectancies and their ages at first breeding are known from ringing, but daily life at sea is shrouded in mystery. Do parents offer support to their chicks when at sea, or must youngsters learn to fend for themselves? Up to now, scientists have been unable to study seabirds during this phase of life, but new technologies are beginning to lift the veil.
Our paper on species- and sex-specific differences in auk diving behaviour was a #TopDownloadedArticle in @AvianBiology last year, woo. Check it here: https://t.co/ZEWlX9py8J. pic.twitter.com/aTkoVc5wfI
— Ruth Dunn (@Ruth_EDunn) April 30, 2020
Researchers from the University of Liverpool fitted tiny depth-recorders to the legs of puffins and other auks on the Isle of May off Scotland. The devices recorded the depths to which the birds dived. They were recovered the following year, when the birds were recaptured back at their nests, and the data logged by the trackers were retrieved.
The puffins, the analysis showed, had dived a great deal, even when they were no longer feeding chicks. That they have to work hard to feed themselves during winter is an important finding. The species is in decline. Could food shortages be responsible? Puffins can dive to great depths but most remained within 15m of the water surface. Is a scarcity of their traditional prey, deeper down in the sea, forcing them upwards?
Guillemots hunted more frequently than did puffins and males made deeper dives of longer duration than did females. They did so, the researchers conclude, because fathers are feeding the chicks that accompanied them from land. Whereas a puffin has only one mouth to feed, a male guillemot may have two.
Like Nagel’s bats, birds’ ways are not our ways.
