Gannet population continues to thrive despite human threat to its numbers

Someone has pocketed my lovely gannet’s skull – well, probably not, but it seems to have disappeared from the years-old jumble of tideline ossuary on the living-room windowsill.

The giant spider crab’s skull still looms there, complete with 2-foot pincer claws. And the tiny skull of a curlew, with a curving tendril of beak. Even the little turtle’s skull in its see-through chocolate box – though, now I come to think of it, it seems to be in bits.

However: "It was the skull I wanted, a sculptural form, the sightless sockets and that great piercing bill." That's Kathleen Jamie, the Scottish poet, in Findings, her joyful book on the natural world of the Hebrides.

An ardent beachcomber like me, Jamie hacked off the head of a washed-up gannet with her Swiss Army knife and dunked it in acid, which didn’t work too well. My skull was delivered by the sea, clean and bleached to ivory.

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“Bone is subtle and lasting” was a Jamie quote from the great George Mackay Brown.

What sent me looking for it was a research paper called How seabirds plunge-dive without injuries, of which the gannet had to be prime subject. Anyone who has watched the birds plunging vertically from the sky to seize mackerel deep beneath the surface must marvel at their anatomy.

A seven-strong study team subjected a 3D printed gannet skull to elaborate, formula-strewn tests of mechanical force and impact to conclude that diving at some 24 metres per second and hitting the sea without buckling that slender neck needs strong muscles behind the skull.

Indeed, by their calculations “it would take about 80m/s for the plunge-diving seabird to sustain a neck injury”.

The northern gannet population, meanwhile, is still on an upward trajectory despite human threats to its numbers. Its breeding colonies now reach as far north as the Svalbard archipelago, following the spread of mackerel to waters off east Greenland and Iceland.

The human threats are physical: entanglement with the polypropylene cord now lining almost every nest, drowning while hooked on underwater longlines. Another potential threat is the loss of food as trawlers stop throwing “discard” fish overboard under new EU regulation; gannets have been the leading scavengers, following astern.

This takeaway food supply must, indeed, have helped produce the increase in Ireland’s breeding colonies. The Irish population has more than doubled since the counts of Operation Seafarer in 1970, reaching almost 48,000 by 2014.

The oldest colonies are at Co Wexford’s Great Saltee, Co Cork’s Bull Rock and Co Kerry’s Little Skellig. The most recent, credited to “overspill”, are on Dublin’s Lambay Island and Ireland’s Eye and at Co Mayo’s Clare Island. All have made gains in the past decade, but those on the Great Saltee, within easy reach of trawlers fishing the Celtic Sea, have almost doubled since 2004.

How do you count birds packed so tightly above sheer island cliffs, their colonies reeking with the annual whitewash of guano? These days it’s from aerial photographs, but a recent book has reminded me of some heroic censusing in the past.

The writings of Michael Kirby, once of Ballinskelligs, Co Kerry, have offered great connection to a lost Gaelic world a lot closer to nature. His past books are long out of print, but Lilliput Press has now published a generous compilation, with some of his paintings and poetry, in Skelligs Haul (€15), edited by Mary Shine Thompson.

As a currach fisherman in the 1930s, Kirby found himself giving personal assistance to a British “bird woman”, unnamed but “six foot three inches tall and broad in the beam – a miniature Amazon”. She had to land on Little Skellig and climb the cliff-face to photograph the mass of 20,000 gannets on the top.

The descent was, if anything, more difficult, and at the really tricky bit, writes Kirby, “I stretched my arms above me until I got both my palms under the cheeks of her buttocks, just as she would sit on a chair”. Glancing fearfully upwards, he found her descending upon him “like a great parachutist clad in black knickers”.

I have been unable to identify the woman, “getting on in years and not so nimble any more”. Her counts of gannets in Ireland were part of an early seabird census of these islands. But her ready and enthusiastic talk, as Kirby helped her move about the summit, sparked the lifelong interest in birds that would enrich his writing in old age.