Cory’s shearwaters show long-distance qualities

Cory’s shearwaters show long-distance qualities

I

see that a website describes the call of Canarian cory’s shearwaters as ‘waca waca’. It’s a mad, hysterical call, uttered when the parent birds arrive to feed their nestlings. They tour overhead, screaming their waca waca while their offspring echo it to tell where they are in the darkness.

I wonder if it’s like the baa of sheep, the distinctive cries of ewes to their darling lambs, and the answering baas of the darlings.

From the shores of South Africa or the coasts of South America, the adults fly over thousands of kilometres of open ocean to return to this island of La Gomera in May. Here, they are known as ‘pardelas’, and reoccupy traditional nest sites in burrows on inaccessible cliff tops up to 320m above the sea. They have not touched land since leaving the year before. They hatch a single white egg in June.

It is after the hatch that the nightly racket begins, loud enough to be heard a kilometre away from their nesting sites. It signals a triumph. They are back again and blessed with family, a single but much valued child.

It is an event raucously celebrated every night throughout the rearing. The adults, after the day spent hunting on the local ocean, come in the dark of night to feed their chicks, their day’s catch of squid or pelagic fish regurgitated into hungry beaks.

Feeding at night is a protective measure. Predatory gulls would be only too eager to attack and seize the squabs if they could locate the nests. However, when darkness falls, gulls go to roost and the chicks can be safely visited.

Around the cliff wall, adult birds swoop and cry for hours on end, weaving like ghostly shadows. I’ve seen them on a moonlit night, and thought it extraordinary that they didn’t collide in flight, so wild and madcap they seemed.

They are strong birds, but awkward on land, with weak legs. For crossing oceans, as they do, evolution has skilfully equipped them. Their width of their wings is 125cm, twice the length of their bodies. On such wings they can ‘shear’ the ocean effortlessly, and for months on end. To rest, they alight and swim, for they have webbed feet.

When the young are fledged, the parents leave them to fend for themselves and go back to their ocean wandering. Cory’s shearwaters from La Gomera may next be seen off the Cape of Good Hope in South Africa and later off Las Arenas at the tip of South America. However, they will be back on the cliffs south of Las Vueltas in La Gomera in time for nesting season the following year. ‘Las Vueltas’, indeed. ‘Vuelta’ means the ‘turn around place’ in Spanish: perhaps it was named for the birds.

All of the 30 shearwater species are long-distance migrants. Sooty shearwaters migrate from the Falkland Island in the South Atlantic to the coast of Norway in the North Atlantic, travelling 64,000km each year. Short-tailed shearwaters fly there and back from Tasmania to Alaska annually.

Shearwaters are not only well travelled but long lived. The facts are astounding. In 2004, an analysis of a Manx shearwater breeding on Copeland Island, Co Down, concluded that it was 55 years old, the oldest known wild bird in the world. Because the species migrates 10,000km to South America every winter, it would have covered 1,000,000km in its life time on migration alone, never mind flying around Irish waters.

The young fledged in Gomera, like those elsewhere, follow the parents north, south, east or west; in the course of four to six years wandering, they may reach the Indian Ocean but will come back to Gomera to nest.

Sometimes, however, before they ever get going, these youngsters get themselves into trouble, attracted by the harbour lights and ending in a dangerous crash landing in the village nearby. However, rescue is at hand. Notices are posted in the vicinity of the nesting sites telling the public what to do if they find a downed pardela.

The possibility of liftoff, with a dazed head and weak legs, is unlikely, and the first thing for the finder is to take the foundling out of the reach of cats or dogs.

There is, then, a rescue service that can be contacted that will care for it and, when it is ready to fly again, relaunch it.

The same service exists in Tenerife, Lanzarote and the other islands. A rescued bird can even be taken into custody by the Guardia Civil.

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