Problems Caused by Certain Sea Birds

 On many islands where birds were strictly pro-tected in wildlife reserves, certain species began to multiply rapidly. This was true particularly of various species of gulls. Thus, for example, on the island of Walney off the Northwest coast of England, there were only 120 pairs of herring gulls in 1947 and today there are some 17,000 pairs. Another colony, on the Isle of May off Scotland's east coast, started with only several pairs of herring gulls in 1907, in 1936 455 pairs of birds nested there, in 1954 3,000 pairs, in 1967 some 11,000 pairs and today more than 15,000 pairs. Until recently the herring gull was protected throughout the whole year also on the coasts of Germany and other European maritime countries. In the German Federal Re-public and Denmark, however, it multiplied considerably. The same thing happened on the islands of Memmert, Mellum and Langeoog where about 3,000 pairs of birds nested in 1906 but by the 1930s this number had grown to 30,000 pairs. Herring gulls on these islands made it impossible for other species of birds to nest there. The same thing happened in the islands of the North Sea. Here the herring gull had practically no natural enemies, what with the decline in the number of raptors. However, even on the neighbouring islands, which were breeding grounds of terns, ducks and other birds, these species were unable to rear their young successfully for the herring gulls flew there and robbed their nests of eggs and nest-lings as well. For this reason it is now permitted to kill this gull in the German Federal Republic between 1 August and 31 March and collect its eggs until 15 June. In recent years, however, the herring gull has also settled on the Baltic coast where it previously nested only rarely. Today the coast teems with thousands of pairs of these gulls. They have also begun to multiply in large numbers on the coast of southern Sweden, where they cause great damage to the nests of ducks and other birds. Thus, conservationists here are also considering regulating their number by collecting their eggs.

The great black-backed gull, which until re-cently was a rare nester on Europe's shores, has also begun to multiply rapidly as a result of protective measures. In England and Wales its numbers were very low, no more than 1,200 pairs nesting there in 1930. Today, however, the number has risen to more than 2,200 pairs. It has shown the same rapid increase on the east-ern coast of the United States, where it nested for the first time in 1916. This large gull feeds mostly on the eggs and young of other sea birds and gulls, fish remnants, fish and mammal car-rion, young and sick rabbits, also refuse and scraps. An overpopulation of these gulls on some offshore islands may entirely decimate the other sea bird populations. In places where terns nest they comprise as much as fifty percent of the gulls' diet. In one colony of avocets nesting on the English island of Havergate, a bird sanc-tuary belonging to the Royal Society for the Protection of Birds, great black-backed gulls were responsible for killing practically all the young one-year.

In the Camargue in southern France, narcotics were added to bait used to control the gulls and in some places in Holland bait was poisoned with strychnine, but this is a very dangerous method because poison baits, alas, do not dis-criminate amongst the victims and thus many other species of birds have been killed by them as well. There is also the danger of other carrion feeders eating the dead gulls. Another method that has been tried is the use of a sterilisation drug.

In recent years it has also become necessary to reduce the number of common gulls on certain offshore islands as they, too, have been causing much damage to other birds, primarily by rob-bing their nests of eggs and young nestlings.

Certain species of gulls that have settled in coastal towns, e. g. the blacklegged kittiwake, are also proving troublesome because they nest on buildings and their droppings cause unsightly damage.

These problems caused by certain sea birds show how disastrous can be the results when the ecological balance is disturbed. First and fore-most is the absence of raptors that serve to regulate the numbers of sea birds. Their protec-tion is therefore one of man's foremost obliga-tions.

 

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