Disastrous summer for terns

Monday, September 24, 2012

AT this time of year terns gather on our local beach for their annual Árd Fheis.

Huddled together, they face into the wind, adults and young of several species rubbing shoulders in the flock.

Dogs disturb them occasionally and the little seabirds fly around noisily before settling on the sand again. Similar gatherings occur elsewhere around our coast. In 1970, 12,000 terns were recorded at Scolt Head in England. Do these gregarious and vocal birds exchange tern gossip or tell tall fishing tails? If so, the theme of this year’s conference must surely be the recent awful weather.

We have five tern species in Ireland. The sandwich tern, with its black bill, is the largest. Noisy and conspicuous, it’s easy to identify. The same can’t be said of the three medium-sized species; they look alike to the casual observer. Two of them, the ‘common’ and the ‘arctic’, are so similar that even keen bird watchers get confused and refer to them jointly as ‘comic’ terns. The little tern, much smaller than the others, is unmistakeable.

The autumn gathering is a welcome break, particularly for the adult birds. The frenetic activity of the breeding season is over. Those that didn’t lose their chicks are saying goodbye to them and the great southward migration beckons. Most will head for the west coast of Africa, but arctic terns can travel beyond the Antarctic Circle. They see more daylight each year than any other creature.

The birds of gardens and the countryside fare badly in wet weather. Keeping chicks dry is a challenge and the insect larvae, the chicks need, can be hard to come by. Terns, being seabirds, should be less vulnerable, at least as far as food gathering is concerned, but rain is still a threat. The adult plumage is water-proof, but the fluffy downy coats of newly-hatched chicks let in the rain. Nests, on the ground amid sand-dunes and shingle, are vulnerable; whole colonies can be washed away. So how did our terns fare during this turbulent summer? Terns breeding along the east coast tern are relatively easy to monitor.

According to Steve Newton of BirdWatch Ireland, the Kilcoole little tern colony had 86 nests at the beginning of June. BirdWatch staff and volunteers fenced them off to keep crows and foxes out and a 24 hour security presence was maintained. Unfortunately, little could be done about the weather. Heavy rain washed out 79 of the early nests. Replacement clutches were laid and by mid-June there were 23 active nests. Alas, easterly winds, an exceptionally high tide and marauding grey crows destroyed them all. The little tern colony at Baltray, County Louth, suffered a similar fate. About 124 nests were destroyed at Rosslare. 2012 has been a disastrous year for little terns.

Two granite outcrops protrude into the sea, seven kilometres northeast of Skerries. These rocks, less than a hectare in extent, hold the largest breeding concentration of roseate terns in Europe. Like the little tern colonies, Rockabill is managed by BirdWatch with the support of the National Parks and Wildlife Service. There were 1,208 roseate nests this year, a slight increase on 2011. Rain killed many of the chicks but, thanks to the pupils of Balbriggan Community College, all were not lost.

Tern nest-boxes made by the wood-work class are of the enclosed type; they keep out the rain. Steve Newton thinks that most pairs raised at least one chick. The two other tern species which nest at Rockabill also benefited. There were 2,007 pairs of common terns and 157 pairs of Arctic terns there this summer.

Not all failures can be blamed on the weather. Two mooring buoys in Dublin port have been managed for terns in recent years. Steve Newton had ringed almost 500 chicks by early July. Then the little colony was attacked. Chicks’ heads were bitten off.

The chief suspect is a rat, or perhaps several rats, but reaching the nests would not have been easy for such a small mammal; the platform is 100m offshore and six metres above the water at low tide. There is a steel ladder. BirdWatch is planning extra protection measures for next year.

* East Coast Terns; how nesting terns fared in their Irish Sea colonies in 2012. Steve Newton. Wings, Autumn 2012. Home