Prosperity off the north Dublin coast

WITH the current gloom and doom it’s a relief to have something positive to write about. Bank accounts may be empty and begging bowls back in vogue but there’s prosperity off the north Dublin coast; the tern colony on Rockabill has broken all records.

According to Dr Steve Newton of BirdWatch Ireland, 1,052 pairs of roseate, 1,796 of common and 345 Arctic terns, nested there this summer; 3,193 pairs in total. It’s incredible that so many nests can fit on this tiny island. There were about 500 of them 20 years ago and it seemed crowded even then. This lump of granite, divided by a narrow channel, protrudes from the sea 6km east of Skerries. Only 0.8 hectares in extent, it supports one of the most important sea-bird colonies in the world.

Terns are little gull-like birds, greyish-white with black skull-caps. Great flyers, they spend much of their time in the air. We have five species in Ireland. The largest, the sandwich tern, is easily recognised; its black bill has a white tip. It must be the world’s noisiest seabird but what terns are saying to each other as they plunge-dive for fish is a mystery. The little tern, our smallest species, is also easy to identify; it’s tiny and has a bright yellow bill. The other three terns, however, are difficult to tell apart even for ornithologists. They are much the same in size and have red and black bills. Roseates are paler, with shorter wings. Their bills are black except for a red base. The name comes from a rosy tint on the breast which fades early in the breeding season. Common and arctic terns are reasonably abundant but roseates are not. Only about 2,000 pairs nest in Europe.

Roseates spend the winter off the coast of west Africa, patrolling the sea like submarine-hunting aircraft and diving on small fish which venture close to the surface. Each spring, they head northwards to Europe. They seem to like the Irish Sea. They used to nest in Wales and there are still colonies in Wexford and Brittany. About a thousand pairs breed in the Azores. Rockabill, however, is the jewel in the roseate crown.

In 1860, a lighthouse was built on the rock, although the one there today dates from 1900. Access is forbidden except for teams from BirdWatch Ireland who protect the birds around the clock.

Terns nest on the ground among clumps of tree mallow, a tall large-leafed plant which grows on flat areas of the rock. Some decades ago, the lighthouse keepers chopped down all of the mallow, to tidy the place prior to a visit of the Lights Commissioners. Terns are notoriously temperamental and it’s a miracle they did not desert the site. Nowadays, the mallow is trimmed back by the voluntary wardens; terns like to nest only around the edges of clumps.

BirdWatch is to be congratulated on the success of the Rockabill colony but so also must the staff and pupils of Balbriggan Community College. In a scheme organised by teacher and ornithologist Sean Pierce, they have been making tern nest-boxes for many years. Almost 700 boxes are now placed annually on Rockabill, extending the potential nesting area. Arctic and common terns don’t lay in them, although their babies use them as shelters. These species, according to Steve Newton, are used to the cool conditions of northern latitudes and don’t need boxes.

Terns may be temperamental but they’re no daws. On a visit to Rockabill to ring terns some years ago, we took along a stuffed stoat. Placing the stoat on a wall of the lighthouse compound, we erected a mist net nearby. Terns are very aggressive and ringers must wear hats to avoid lacerations to the scalp from irate dive-bombing parents. We expected that the stoat would receive similar treatment and that terns would blunder into the net in their fury. They ignored the fake intruder completely, however, and not a single one was caught.