LITTLE terns began nesting at Crimdon, near Hartlepool in Teeside, in the mid-1990s.
Sixty-five pairs did so this year. Volunteers protect the colony but there isn’t 24 hour surveillance. On the morning of June 19, according to a BBC report, a warden discovered that the eggs had been stolen from fifty nests. They were two thirds of the way towards hatching so the chicks inside them would have been well formed. Large footprints in the sand showed that the raid was carried out by a man acting alone.
Sometimes called ‘sea swallows’, terns resemble delicate little gulls with black skull-caps. The plumage is pale grey above and white underneath. Not much bigger than a starling, the little tern is the smallest of the world’s 44 species. Its bright yellow bill makes identification easy. The birds which visit our part of the world spend the winter off the west coast of Africa; ringed ones have been found as far south as Ghana. Adults return in April and May. They like to nest on coastal shingle beaches, or shell-strewn sandy places, with stretches of clear water, salty or fresh, close by. There has to be a plentiful supply of little fish, food for the chicks. No nest is built; the eggs, beautifully camouflaged, are laid on the ground.
In 2012, there were 110 nests at Crimdon. All failed. The culprits then were natural predators. Crows, mink, rats, foxes, hedgehogs, sparrowhawks and kestrels take tern eggs and chicks. Which of these were responsible for the 2012 destruction isn’t clear.
Researchers Jane Sears and Mark Avery found that the number of nests at a colony fluctuates from year to year, suggesting that not all pairs are site faithful. Terns, it seems, are willing to ‘shop around’ when it comes to breeding sites. Last year’s disaster, therefore, may be partly responsible for the reduced numbers at Crimdon this summer. Will the recent egg theft result in further declines?
Colony desertion is a real possibility with terns; like dissatisfied shoppers, they may take their custom elsewhere if they don’t get what they want. The sand dune peninsula known as Malahide Island had a celebrated breeding colony. All five Irish tern species bred there. Records speak of ‘several thousand’ common terns and ‘very large numbers’ of Arctic terns. Then the sand-banks shifted off-shore and nests were swamped at high tide. By 1955, they were gone. Between 1968 and 1972, we had 16 colonies along the coast between Dublin and Waterford. Only eight remained in 1987. Disturbance by sunbathers and dog-walkers was mostly to blame.
Little terns remain in southern waters for their first few summers. They don’t come north to nest until they are at least two years old. Youngsters raised two years ago might return to Crimdon and help keep the colony viable. On reaching breeding age, migrant birds often visit the place where they were raised. However, we don’t know to what extent young terns choose their natal colonies when breeding for the first time. Only by ringing enough birds could we hope to find out.
Tern chicks are easy to ring; their colonies are accessible. However, discovering where ringed chicks go once they have fledged is a ‘needle in a haystack’ task; only 1.2% of ringed little terns are ever found. It’s clear that some chicks at least aren’t faithful to their natal colonies.
There are about two dozen little tern breeding sites here. BirdWatch Ireland and Louth Nature Trust keep a constant vigil on two of the most prominent and vulnerable ones.
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