BRAAKSMA S (1964) Preventing the Common Gull Larus canus. LIMOSA 37 (1): 58-95.

Common Gull Larus canus canus In 1962 an investigation was made by collaborators of the State Forest Service with regard to the distribution of the Common Gull, Larus c. canus L. It is very likely that this species has already been breeding on two places in the Netherlands (Texel and De Beer) as early as the second half of the past century. However no further data on these breeding cases are available. This is the reason why the first officially registered dutch breeding case dates from 1908. Since this first case on the isle of Rottumeroog, the number of breeding pairs and the number of breeding areas have steadily increased. In 1962 the Common Gulls are known to have bred on at least 26 places. In most of these areas the species is a regular breeder now. The present number of breeding pairs in the Netherlands amounts to at least 660. Noteworthy are some "inland"-breeding cases: Ossendrecht (1936), Noord-Oost Polder (1946 and 1953), Millingen (1960 and 1961) and Dorplein (1961 and 1962). The increase of the Common Gulls in the Netherlands is an inevitable result of a general increase of the breeding areas of the species in Europe. This increase is also discussed in the article. The author suggests that the large scale egg-collecting in some of the biggest german breeding colonies might be one of the causes of the increase of the number of breeding areas on the continent. The Germans succeeded for instance in reducing the total number of breeding pairs in the overcrowded colony at Langenwerder from 8000 into 3000. This may have caused a large scale migration to other, more quiet, breeding areas. Common Gulls are only to a very low degree selective with regard to the choice of their breeding habitats and the search of their food. Yearly increases of the number of breeding pairs by more than 70% are not unfrequent. Those circumstances enable the species to recover from the severe losses in some of the breeding colonies. Humans excepted, faxes and rats seem to be the worst enemies of the Common Gulls in some breeding colonies. This has for instance been proved in soi;TIe german breeding colonies. In other countries Hooded Crows, Crows and Herring Gulls seem to do pretty much damage by robbing eggs and young birds. In Holland thus far only a slight predation by Herring Gulls and Crows has been stated. On their turn however, the Common Gulls have proved not to be as gentle as they look. Many nest-robberies at the cost of other gulls, terns and waders bear this out. As a result the author regards the increase of Larus canus with mingled feelings and concludes his article with the suggestion that, if necessity arises, the dutch ornithologists should not hesitate to gather Common Gull-eggs in colonies, where too much damage is done to other breeding species. An interesting detail of the facts gathered on the distribution in other countries, is that in the Leiden museum there is a clutch of 3 Common Gull-eggs, collected by the Englishman Dunn, on Iceland in 1861. In the available literature the Common Gull is not considered to have bred on Iceland before 1955! A total of 364 recoveries of Common Gulls ringed in the Netherlands, or ringed in other countries and recovered in the Netherlands, proves that in this country there are some very important winter areas for birds from all countries of the european continent. Especially the northern provinces (Groningen, Friesland and Noord-Holland) have proved to be very attractive in autumn and winter. Most of the rings recoverer! in the Netherlands have proved to be of swedish origin. German, danish and norwegian birds follow in the 2nd, 3rd and 4th place respectively. Besides there are rather many recoveries of finnish birds. Of 17 russian birds 16 proved to have been reared in the baltic area, mostly in Estland. The farthest recovery known up till now, is that of an adult Common Gull, caught and ringed in the month of january at the Hague and recovered in june of the same year at Pudorj (U.S.S.R.), near the White ~ea. This bird might belong to the different russian form of the Common Gull! Some ringing results might indicate the possibility of german birds breeding in the Netherlands. However, there is no prove, that this is really true. Two swedish birds, II and 13 years old, recovered in the Netherlands in april and june, might possibly have been to old to breed. Three birds ringed as nestlings in dutch breeding colonies have been recovered in northern France in september of the same year. Another bird was recovered in its first year in the neighbourhood of Bordeaux in january. A 5th bird has been recovered in Portugal in february. Besides there are 2 winter-recoveries of dutch birds in England and some winter-recoveries in our own country. These results indicate, that a great part of the dutch birds stay in southern countries during winter. England evidently belongs to the winter-area of the dutch birds as well. Important are the recoveries of 13 adult birds during the breeding-season: 8 of them returned to the areas where they were hatched, 5 others possibly migrated to other dutch breeding colonies (2 in a northern and 3 in a southern direction). As to the average age of Common Gulls: of 364 recoveries 42% of the birds proved to have been recovered in the year in which they had been ringed, 23% in the 2nd year, 12% in the 3rd year and 23% had been older. The eldest bird was recovered after 15 years.

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