Collared Doves in Britain and Ireland During 1965-70 Robert Hudson
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Collared Doves in Britain and Ireland during 1965-70 Robert Hudson INTRODUCTION The Collared Dove Streptopelia decaocto was first found nesting in these islands in 1955, and a summary of the subsequent spread over Britain and Ireland up to the end of 1964 has appeared previously (Hudson 1965). The present paper continues the story up to the end of 1970. Though the Collared Dove has, in the space of a very few years, become so widespread and locally numerous as to be taken for granted by British and Irish birdwatchers, it is salutary to remember that at the time The Handbook appeared in 1938-41 the species was breeding no nearer than Hungary, Czechoslovakia and Austria. Yet by 1949 it had reached the North Sea (the Netherlands) and Scandinavia (Denmark, Sweden); and by 1959 it was resident in all European countries except Iceland, Finland, Spain and Portugal. Detailed summaries of the European spread were given by Fisher (1953), Stresemann and Nowak (1958) and Nowak (1965). I am not aware of any Collared Dove records as yet from Spain or Portugal; but there are indications of a continuing north and north westward spread. A few pairs are now nesting in south Finland (Ojala and Sjöberg 1968). Several birds were present at Torshavn in the Faeroe Islands during summer 1970, though nesting was not proved (per K. Williamson). One came ashore from a fishing boat at Lodmundarfjörd, eastern Iceland, in August 1964 (Langseth 1965), and two pairs nested in southern Iceland in 1971 (per Dr B. Campbell). The rapidity of the species' spread across an entire continent is almost without precedent; the only comparable case in historical times concerns the colonisation of the New World by the Cattle Egret Bubulcus ibis. THE SPREAD IN BRITAIN AND IRELAND IN I965-7O Collared Doves began nesting in England in 1955 (Norfolk), Scotland in 1957 (Morayshire), Ireland in 1959 (Dublin, Galway), Wales in 1961 (Cardiganshire, Pembrokeshire), and the Isle of Man in 1964. By 1964 the species was resident in 34 counties in England, eight in Wales, 20 in Scotland and twelve in Ireland, and was therefore widely dis tributed over these islands, including western parts. Since then it has essentially been infilling between established centres (especially by spreading into less favoured rural habitats), and this it is doing fairly thoroughly. The only major 'first' during 1965-70 was the colonisation 139 140 Collared Doves in 'Britain and Ireland 196J-J0 Table 1. Number of counties in Britain and Ireland in which Collared Doves Slrtptopelia decaocto had been (a) recorded and (b) proved breeding by the end of 1970 Total Species Breeding counties recorded proved England 39 39 39 J Wales 3 13 '3 Isle of Man 1 1 1 Scotland 53 33 29 2 Ireland 3 31 27 TOTALS 118 "7 109 of Shetland, where it has bred on Mainland since 1965, while in 1970 a pair nested on Unst, the most northerly British island. Mention must also be made of recent nesting on various other outlying islands, such as the Isles of Scilly, additional ones in the Outer Hebridean chain, and the Aran Islands off Co. Galway. The general situation in Britain and Ireland at the end of 1970 is shown in table 1. The only British or Irish county in which the Collared Dove has not yet been recorded at all is Co. Cavan. There are a further eight in which breeding has yet to be established: Buteshire, Nairnshire, Peeblesshire, Roxburghshire, Co. Leitrim, Co. Leix, Co. Longford and Co. Roscommon. Nesting may, however, be occurring in these eight counties, since the Atlas project of the British Trust for Ornithology has revealed breeding season occurrences in all of them (but see page 145 for a cautionary note). Kent continues to have the biggest breeding concentrations, includ ing one of 1,000-1,500 pairs in the Isle of Thanet. There are also very large numbers in the adjacent county of Sussex, notably at least 400 pairs in the eight square miles of the borough of Bexhill (see below). These major south-eastern centres are now rivalled in size by one in Lancashire, where the species has become locally abundant in the near-coastal region between Liverpool and Southport—a very large feeding concentration in a pheasant covert at Formby during cold weather in February 1970 was said by the gamekeeper to have numbered 2,000-3,000 individuals; local birdwatchers were unable to confirm this, being denied access to the covert, but were impressed by the large numbers of Collared Doves flighting back and forth. Special mention must also be made of one Irish district—the Tralee area of Co. Kerry—where there are increasingly large numbers and a flock of 500 has been reported, the highest Irish concentration. One cannot fail to be impressed by the continuing concentrations of breeding numbers in coastal and near-coastal areas, such as are clear Collared Doves in Britain and Ireland 19 6J-J 0 141 from fig. 1 and the county summaries below. In virtually all maritime counties the largest numbers of Collared Doves occur within five miles of the shore, so that it has proved necessary for the purposes of this paper to define 'inland' as over five miles from tidal water. The causes of this trend towards high coastal and near-coastal densities are COLLARED DOVE 30.3.71 JTRS Fig. I. Breeding distribution of the Collared Dove Streptopelia decaocto in Britain and Ireland in 1970 (prepared by Dr J. T. R. Sharrock from preliminary data gathered for the Atlas project of the British Trust for Ornithology). Each dot denotes presence in a 10 km X 10 km square of the National Grid. The largest dots represent confirmed breeding records, the middle-sized dots denote probable breeding, and the smallest dots represent breeding season records of uncertain status (see page 145). Note the concentration in coastal and near-coastal districts, and the scarcity in or absence from upland areas 142 Collared Doves in Britain and Ireland ip6j-jo a matter for speculation. Perhaps the initial dispersal pattern was responsible, at least in part: coasting movements (including those by immigrant birds from the Continent) would lead to first county breeding records in coastal districts, to be followed by patterns of local expansion prior to inland spread. Another likely factor is the Collared Dove's preference for lowlands: if fig. i on page 141 is compared with a relief map of Britain and Ireland, it will be seen that the majority of breeding areas are below the 500-foot contour, and very few are above 1,000 feet. Away from East Anglia, the Fens and the east Midlands of England, most counties have extensive inland areas of downland, moorland or mountain from which Collared Doves are absent or (at best) which they treat as marginal habitat, whereas most near-coastal land is relatively low-lying with considerable human populations (with which the doves are commensal) and is therefore optimum habitat. Though the species is spreading into rural areas, it remains thinly distributed in such situations, with a few local exceptions (for example, at granaries, makings, chicken farms and game-rearing establishments, where grain is accessible to the doves). Consistently, the largest numbers of breeding Collared Doves are present in suburban and, to a lesser extent, urban areas, and a quantified example may be quoted. In 1968 J. A. Hicks made a sample-count survey of the species in the borough of Bexhill, Sussex, and produced the results shown in table 2. The densities there are high by national standards, but there is no reason to think that the proportions in each type of habitat are unrepresentative. The general indication is that die number of breeding doves near the centre of a town is inversely correlated to the size of its built-up area, so that normally the birds are absent from the hearts of major British towns and cities. There are a few exceptions: they are present in Edinburgh (a spacious, non-industrial city), in Liverpool (where Table 2. Broad habitat preferences of Collared Doves Streptopelia decaocto in the borough of Bexhill, Sussex, in 1968 Area in Estimated num Pairs per Habitat type square miles ber of pairs square mile Urban: built-up areas, small or no gardens it 60 40 Suburban: small to medium-sized gardens 2 128 64 Suburban: larger gardens 2 176 88 Peripheral farmland and woodland 2l 40 iG TOTAL 8 404 Collared Doves in Britain and Ireland 196J-70 143 they feed at a grain-store behind Exchange Station), and in Hull. But despite being common in the suburbs of so many other cities (Manchester, Leeds, Sheffield and Birmingham, for example) they do not breed in the central districts, while there is no obvious reason for their failure to colonise the spacious Royal Parks of Inner London. This contrasts with the situation elsewhere in the European range, where Collared Doves are often present in city centre open spaces. POPULATION TRENDS AND THE FUTURE The Collared Dove population of Britain and Ireland increased geometrically from 1955, totalling at least 19,000 birds by the autumn of 1964, in which year the number of breeding pairs was probably about 3,000. This virtual doubling of the population year by year led me to predict (Hudson 1965) that, in view of the barrier to further expansion imposed by the Atlantic Ocean, there would be a very big build-up in Britain and Ireland since the birds would be unable to disperse any farther westwards. Time has proved this prediction wrong. It is unfortunate, though doubtless inevitable, that the degree to which Collared Doves are now taken for granted by most birdwatchers means that it is no longer possible to treat quantitative aspects of their distribution in the exact manner used in my previous paper: the basic numerical information has not been forthcoming in sufficient detail.