The Birds of Orkney David Lea and W
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Volume 68 Number 7 July 1975 The birds of Orkney David Lea and W. R. P. Bourne This paper was read at the Nature Conservancy Council Symposium on the Natural Environ ment of Orkney, held in Edinburgh on 2 6th-27th November 1974. The only major alteration is the omission of an appendix which gave the number of pairs of seabirds breeding on the different islands during the Seabird Group's national breeding census, 'Operation Seafarer', in 11)69-70. This appendix is reproduced in the Proceedings of the Symposium which have now been published by the NCC, is Hope Terrace, Edinburgh EHO, 2AS. The editors and authors are grateful to the NCC for permission to reprint this paper. Eddie Balfour was to have been a joint author but died suddenly in August 1974; his unrivalled knowledge of the birds of his native county would have added greatly to the content. While it is a poor substitute for his personal involvement, he left many published and un published notes and it would have been difficult to write authoritatively without these. His study of the Orkney Hen Harrier population represented the longest study of a bird of prey population anywhere in the world and is the subject of a separate contribution to the NCC Symposium {Balfour andCadbury 1975). INTRODUCTION The character of an island bird community is determined by the latitude and climate, the size, ecological diversity and isolation of the island, and the numbers of potential immigrants and their freedom from persecution. The information available on just over 300 bird species recorded in Orkney has already been summarised by Balfour (1972), and their character and that of the different islands were discussed by Lack (1942-43). This paper analyses the avifauna in terms of bird communities, with particular emphasis on the breeding species and common passage migrants and winter visitors. The communities have been denned on a rather broad and arbitrary basis because members of the same association are liable to frequent many different habitats (described by Bullard and Johnston 1975) and any detailed subdi vision is difficult. 261 262 The birds of Orkney The proximity of all parts of Orkney to the sea exerts a profound influence on the birds: gulls are the commonest breeding birds on many moors, Fulmars* are one of the main foods fed to their young by the Golden Eagles on Hoy, and many of the birds found on farm land feed and roost along the shore, whereas coastal species are likewise liable to feed or roost on farmland. THE PRESENT SITUATION The species which have bred regularly in the last five years, and some common visitors, are listed and their habitat preferences assessed in appendix 1 on pages 280-282. A comparison is made in table 1 with the breeding birds of Caithness and Sutherland, Shet land, and the Faeroes, much of the Scottish information being taken from Parslow (1973) and that for the Faeroes from Williamson (i97o). It will be noted that there are 37 species breeding in the two northernmost counties of the Scottish mainland that do not breed in Orkney, only 10 km (6 miles) to the north. About 17 of these are associated with trees, which were almost eliminated at one stage and are still scarce in Orkney, though 15% of the breeding birds nest exclusively in this habitat or associated buildings. This deficiency of sites has caused such species as the Kestrel and Woodpigeon to start nesting on the ground (Balfour 1955). There appears to be suitable habitat for most of the other missing north Scottish species, and the isolated and fragmented character of the islands or more subtle deficiencies in the environment must account for their absence. This impoverishment of the environment and avifauna is even more marked in Shetland, which in its turn lacks a third of Orkney's breeding species, and in the Faeroes, which lack nearly half. The absence of voles from these northern groups may explain the deficiency of such predators as the Hen Harrier, Kestrel and Short-eared Owl which are quite numerous in Orkney. Some of the species which breed in Orkney are on the margin of their world range (Voous i960), especially such southern forms as the Little Grebe, Coot, Sandwich Tern and Stonechat. However, all the northern species breeding in Orkney also breed elsewhere in the north and west of Scotland, and, in the case of the Red-throated Diver and recently lost Red-necked Phalarope, in Ireland as well. The Purple Sandpiper is the only species breeding regularly in the Faeroes that is not known to nest further south, though it was reported breeding in Shetland in the last century. Similarly, only one species breeding regularly in Shetland, the Snowy Owl, does not breed further south, though the Whimbrel and Red-necked Phal- *Scientific names of birds are listed in the appendices on pages 280-283 The birds of Orkney 263 Table x. Comparison between regular breeding birds of Caithness and Sutherland, Orkney, Shetland, and die Faeroes The status of a good many of these birds in the different archipelagoes fluctuates, and the information for the Faeroes in particular is incomplete and probably not up to date Caithness and Sutherland but not Orkney Black-throated Diver Greenshank Treecreeper Slavonian Grebe Little Tern Redwing Common Scoter Tawny Owl Whinchat Goosander Swift Redstart Greylag Goose Great Spotted Woodpecker Grasshopper Warbler Sparrowhawk House Martin Whitethroat Ptarmigan Sand Martin Wood Warbler Black Grouse Magpie Tree Pipit Partridge Great Tit Grey Wagtail Dotterel Blue Tit Siskin Woodcock Coal Tit Redpoll Wood Sandpiper Long-tailed Tit Bullfinch Orkney but not Caithness or Sutherland Manx Shearwater (Leach's Petrel?) Gannet Orkney but net Shetland Little Grebe Water Rail Sedge Warbler Grey Heron Moorhen Willow Warbler Wigeon Coot Goldcrest Pintail Sandwich Tern Spotted Flycatcher Shoveler Short-eared Owl Dunnock Mute Swan Dipper? Greenfinch Golden Eagle Song Thrush Linnet Buzzard Ring Ouzel Chaffinch Hen Harrier Stonechat Yellowhammer Kestrel Robin Shetland but-net Orkney Common Scoter Red-necked Phalarope House Martin Whimbrel Snowy Owl Fieldfare Black-tailed Godwit Shetland but not Faeroe Wigeon Black-tailed Godwit Skylark Tufted Duck Common Tern Rook Common Scoter Woodpigeon Jackdaw Peregrine Collared Dove Blackbird Corncrake Snowy Owl Corn Bunting Curlew Long-eared Owl Reed Bunting Faeroe but not Shetland Greylag Goose Ptarmigan Redwing Mute Swan Purple Sandpiper White Wagtail 264 The birds of Orkney arope are scarce elsewhere. Other northern and southern birds which have bred occasionally in these archipelagoes have had difficulty in establishing stable populations. This is perhaps due to human interference, but they are likely also to be particularly sensitive to fluctuations in climate at the edge of their range which influence not only their own breeding success but also the supply of reinforcements. CHANGES IN STATUS Table 2 summarises changes in status and lists species which have bred occasionally this century. The existing avifauna is known to have been modified markedly over the course of time by fluctuations in the climate and by human activity. The latter acts both directly Table st. Changes in status of Orkney birds Former breeding species not now breeding Common Scoter (until 1958) White-tailed Eagle (e. 1870) Great Auk (c. 1810) Whooper Swan {c. 1800) Ptarmigan (c. 1830) Sand Martin (c. 1900?) Sparrowhawk (c. 1940) Red-necked Phalarope (c, 1970) Regular breeding species which have decreased this century Manx Shearwater Water Rail Common Sandpiper Grey Heron Corncrake Dunlin Eider Coot Skylark Red-breasted Merganser Lapwing Greenfinch Peregrine Ringed Plover Corn Bunting Merlin Golden Plover Yellowhammer Red Grouse Species which were lost but have returned Golden Eagle (ceased to breed c. 1840 but now breeding again) Dipper (ceased to breed c. 1940 but now probably breeding again) Regular breeding species which have increased this century Red-thrqated Diver Oystercatcher Kittiwake Mallard Curlew Stonechat Shoveler Arctic Skua Reed Bunting Hen Harrier Great Black-backed Gull Species recorded breeding for the fast time since 1800 and now regular Fulmar (from 1900) Buzzard (1961) Rook (after 1850) Wigeon {c. 1870) Great Skua (1915) Goldcrest (c. 1830?) Pintail (1908) Woodpigeon (c. 1840) Tree Sparrow (1961) Mute Swan {c. 1890) Collared Dove (1962) Species which have bred occasionally this century Gadwall Black-tailed Godwit Black Redstart Scaup Greenshank Blackcap Pochard House Martin Garden Warbler Long-tailed Duck Mistle Thrush Whitethroat Quail Fieldfare Wood Warbler Whimbrel Whinchat Grey Wagtail The birds of Orkney 265 through predation and indirectly through changes in the habitat. The National Museum of Antiquities of Scotland has reported the following bird species among the remains found in the very numerous Neolithic and Bronze Age monuments of Orkney, some coming from the later Brochs (Groundwater 1974): Great Northern Diver, grebe sp., shearwater sp. (probably Manx), Gannet, Cormorant, Shag, Bittern, duck sp., Pink-footed Goose, Whooper Swan, Golden and White-tailed Eagles, buzzard sp., falcon sp., Merlin, Curlew, skua sp. (probably Arctic), Great Black-backed, Herring and Common Gulls, Greak Auk, Guillemot and 'Carrion' Crow. While, in common with other archaeological finds, these probably deserve more study, they at least indicate the character of the original avifauna. It will be noted that, in addition to northern forms, they include a southern form, the Bittern; the climate was warm for much of the Neolithic period. Changes within the historic period were documented by Buckley and Harvie-Brown (1891), Lack (1942-43) and Balfour (1968, 1972). These include the loss of such species as the Greylag Goose, Whooper Swan, Golden and White-tailed Eagles and Great Auk due to persecution and reclamation in the 18th and 19th centuries, much as in the other north-east Atlantic archipelagoes. A recent reversal of this trend, owing to a loss of interest in hunting and to the institution of protection, has already brought back the Golden Eagle, and there has been an influx of species associated with human activi ties, including agriculture.