Sea-Birds. James Fisher

Чтение книги онлайн.

      EVERY BIRD has a history, which is a tale of adventure and fluctuating fortunes, of success, or of failure; for every bird, like every other animal, suffers change. In any study of the life of birds, and the place of birds in nature, an understanding of their numbers is fundamental.

      Since most sea-birds are social animals, and nest in colonies in wild and beautiful places, their numbers can often be studied very closely, and with a great deal of enjoyment. So enthusiastic is the average amateur bird-watcher about visiting sea-bird stations, and ‘collecting’ islands, that it is safe to say that every important seabird colony on both coasts of the United States (not Alaska), and on those of the Faeroes, Britain, France, Belgium, Holland, Denmark, Germany, Finland, and Sweden is known to somebody who can distinguish its birds from each other; and most of those in Norway, Spain, Portugal, Iceland and St. Lawrence-Canada are known. The sea-bird stations of Greenland, thanks to a tradition of accurate observers from Giesecke to Bertelsen and Salomonsen, are better known than those of the Canadian Arctic, Newfoundland, the U.S.S.R., China, and perhaps even Japan. Those of the Antarctic and Subantarctic, and South America, are perhaps better known than those of the tropical Pacific. Probably a very adequate list of the sea-bird stations of the United States (excluding Alaska) or of north-west Europe could be compiled by some bibliophilic ornithologist with access to all the local as well as national bird and natural history journals of those countries. Such lists would be useful documents; they would have to be carefully dated, because of what history tells us of the fortunes of animals, and of change. Fisher has recently compiled a dated list of all the fulmar colonies of the world, and we have both, at different times, compiled lists of the world’s gannetries. It is surprising how certain it is possible to be of being complete, within reasonable limits. Thus after the publication of his Report on the 1938 survey of black-headed gull colonies P.A.D. Hollom (1940) had no colony known (or not known) to be occupied in 1938 to add or subtract from his list of 342 such colonies. When Fisher and Vevers (1943–44) organised a census of the North Atlantic gannet in 1939, only two small colonies of the twenty-three which then existed were overlooked in that year. When Fisher and Waterston (1941) reported on the fulmar colonies known to them in Britain in 1939 they believed that there were 208 separate stations at which the fulmars were breeding. Ten years later, after carrying on research and correspondence with the same intensity to discover the situation in 1944 and 1949 (during which ‘back information’ was also collected), Fisher discovered that he had overlooked only nineteen, all small (and some in very remote parts), and unimportant as far as the fulmar’s population, or the actual extent of its range, were concerned.

      A census of the sea-birds of the North Atlantic is no longer a wild dream. A start has been made with certain obvious species, with limited distribution or small populations. The organisational problems are not insuperable; we have an ever-increasing body of highly competent bird-watchers available for, and keen on, the counting of nests: for a sea-bird census depends on the assessment of the number of occupied nests. Such a census has already been performed for several species on the coasts of Germany (Schulz, 1947), and, judging from the descriptions of the distribution of sea-birds in Sweden (Lundevall, unpublished), Denmark (Jespersen, 1946, and Løppenthin, 1946), the Netherlands (van Ijzendoorn, 1950) and Belgium (Verheyen, 1951), it need not be long before a census of the southern North Sea and Baltic could be complete. In Britain good surveys, if not censuses, exist for the sea-bird colonies of most counties in England, and there are records published in the present century concerning almost every bird-cliff in mainland Britain (though not every species on the cliff) and many in the Hebrides, Northern Isles and Ireland. Complete censuses, or careful estimates, have been made of many species of sea-birds in various countries with a North Atlantic-Arctic seaboard; of which a selection is:

      SOME CENSUSES

      of apparently occupied nests (i.e. an approximation to the apparent total breeding pairs) of North Atlantic sea-birds in some parts of their range (in a few cases, world census). Censuses of single colonies are not included unless these are of great importance.

      Fulmar, c. 100,000 in Britain, including St. Kilda, in 1949 (and five-yearly estimates since eighteen-seventies; Fisher, 1952): c.350 in Norway in 1947 (P. Valeur, 1947): c. 200,000 in West Greenland (F. Salomonsen, 1950): c.200,000 on Bear I. in 1932 (Bertram and Lack, 1933): c.100,000 + at Cape Searle, Baffin I. in 1950 (V. C Wynne-Edwards, 1952).

      North Atlantic (Cory’s) shearwater, c.20,000 on the Salvages, pertaining to Madeira, in 1939 (R. M. Lockley, 1952).

      Great (Tristan great) shearwater, world population between 2 and 2½ million, all on Tristan da Cunha in 1949–50 (M. K. Rowan, 1952).

      Cahow, world population all on Bermuda where 13 or 14 nests found and 1951 population “perhaps of the order of 100 adult birds, there may be fewer, but there are not likely to be more.” (Murphy and Mowbray, 1951).

      Leach’s petrel, c.2,000 in Britain; this estimate contains a guess of 1,000 nests on St. Kilda in 1931 which is unreliable since not all the St. Kildan islands on which the species nests were visited (Atkinson and Ainslie, 1940): c.13,000 in Newfoundland in 1942–45 (Peters and Burleigh, 1951).

      American white pelican, world population c.15,000 in 1932 (B. H. Thompson, 1932).

      North Atlantic gannet, world population c.83,000 in 1939, of which c.70,000 in Iceland-Faeroes-Britain; in 1949 c.82,000 in Iceland-Faeroes-Britain (Fisher and Vevers, 1943–44, 1951). See here.

      Double-crested cormorant, Population entire n.e. subspecies P. a. auritus, c.20,000 in ’twenties (H. F. Lewis, 1929); re-established on eastern seaboard U.S. c.1925 (E. H. Forbush, 1925, H. L. Mendall, 1936); c.900 in 1931 (Norton and Allen, 1931), over 10,000 in 1944 (A. O. Gross, 1944).

      European cormorant, in Holland c.1,200 in 1926, c.2,600 in 1934, c.4,000 in 1937, 4,622 (peak) in 1940, 4,359 in 1941 (van Ijzendoorn, 1950); in Belgium 30 in 1950 (R. Verheyen, 1951); in North America 1,086 in 1940 (H. F. Lewis, 1941).

      Great skua, just over 100 in the Faeroes in 1942, c.200 in 1946 (K. Williamson, 1945b, 1948, L. Ferdinand, 1947); c.1,000 in Great Britain (all Shetland and Orkney) around 1946 (R. Perry, 1948, Royal Society for the Protection of Birds watchers and other sources).

      Ring-billed gull, c.1,750 in Gulf of St. Lawrence in 1940 (H. F. Lewis, 1941b.).

      Common gull, c.500,000 in Denmark in 1939 (P. Géroudet, 1946); 20,221 in Germany in 1939 (Schulz, 1947); c.250 in Holland in 1949 (van Ijzendoorn, 1950); a few occasionally on the Belgian border (Verheyen, 1951); c.30 in England in 1941.

      Herring-gull, c.27,500 in Holland in 1938 (van Ijzendoorn, 1950); 28,569 on North Sea coast of Germany in 1939 (Schulz, 1947); under 9,000 СКАЧАТЬ