Greenland Barnacle Geese in the British Isles M. A. OGILVIE AND H. BOYD Introduction the birds. Boyd (1968) gave a full account of the techniques involved and some of the There are two populations of Barnacle Geese difficulties and pitfalls encountered. It is Branta leucopsis wintering in the British sufficient here to state that a light aircraft is Isles. The smaller one, breeding in Svalbard used, flying at about 140 km/hr and at (Spitsbergen) and wintering exclusively in the 150-200 metres above the sea. One or two Solway Firth, has been monitored closely for observers are carried in addition to a pilot- many years (Roberts, 1966; Ogilvie, 1970; observer. Photographs of flocks are obtained Owen & Campbell, 1974). This paper con­ where practicable but are not relied on, as cerns itself with the other, larger population, visual counting by experienced observers has which breeds in East Greenland and in winter been found to be as accurate as and more is found almost exclusively on islands off reliable than photographs, which must often the west and north coasts of Ireland and be taken in very poor light. Scotland. The virtually complete separation Largely because of expense, aerial surveys of the two populations from each other and of Barnacle Geese have been neither regular from a third which breeds in arctic USSR and nor frequent. Partial or complete surveys winters in the Netherlands has been shown by were carried out in 1957, 1959 (two), 1961, extensive ringing (Boyd, 1964; Larsen & 1962, 1965, 1966 and 1973. Those in 1957 Norderhaug, 1964; Salomonsen, 1967). and 1965 were restricted to the Scottish part The Wildfowl Trust has been monitoring of the range and in March 1959 only Ireland the Greenland Barnacle Geese in winter since was covered and then not completely. Boyd 1957, by means of occasional aerial surveys, (1968) gave the results for the Scottish range the majority over the whole range, and by of the first six surveys but did not report on regular counts on the island of Islay in the the Irish figures in any detail. Cabot & West Inner Hebrides that have also included (1973) reviewed the Irish results (though assessments of annual breeding success. Islay excluding March 1959), in the context of the holds a considerable majority of the total pop­ study of the birds on the Inishkeas. This paper ulation. Virtually the only other work on the gives the full results of the 1973 survey and population has been by Cabot on the compares them with the results of all the Inishkeas, the most important Irish haunts, previous surveys. which he has visited almost annually since Barnacle Geese know nothing of boun­ 1960 (Cabot & West, 1973). He has been daries between countries and draw no distinc­ concerned with the population dynamics of tion between Ireland and Scotland. How­ the 2,000-2,500 birds wintering on the ever in this paper the two countries will islands and with looking for factors which be separated if only because their current may affect their use of the islands and shooting and conservation arrangements are breeding success, and is continuing a study of different, and future steps may be taken on a feeding ecology. national not international basis. Censusing a population of birds which winters on nearly 200 remote islands (mostly now uninhabited by man) scattered from Aerial survey results County Kerry to Sutherland must present certain problems. The only satisfactory In the course of the eight aerial surveys Bar­ method is counting from the air. Aerial sur­ nacle Geese have been found on a total o f 169 veys for goose counting were first undertaken islands and (in a few cases) headlands. Cabot in Britain on a regular basis in 1957. & West (1973) list a further 23 Irish sites Although the technique is well known, there where Barnacle Geese have been recorded at are a number of difficulties inherent in flying some time though none were present during off the west coast of the British Isles. Airfields any of the surveys. In some of the archi­ with fuel are few and survey routes have to be pelagos in both Ireland and Scotland the planned accordingly. The weather, which geese almost certainly use all the suitable arrives there less well-heralded than further islands at some time although actual sightings east in the country, often causes tiresome have not been recorded. This will be true, for delays. To these logistical items must be example, in the Sound of Harris, between added the problems of locating and counting Harris and North Uist, where Barnacle Geese 139 140 M. A. Ogilvie and H. Boyd have been recorded from 20 islands during the Blasket Islands, Co. Kerry, into the five con­ aerial surveys but could be expected on vir­ stituent islands, none more than four tually all the 50-60 islands (the exact number kilometres from the next and only two of depends on definition) in the Sound. which have held geese at the times of the sur­ A complete tabulation of the survey results veys, it does seem right to treat them separate­ has been deposited at the Wildfowl Trust. In ly from the next nearest haunt, the Magheree any discussion of the figures, however, and es­ Islands, 43 kilometres to the north-east. pecially in making comparisons between the The map (Figure 1) shows the groupings, years, it is more meaningful to group the while the survey results are given in Table 1. islands according to an, inevitably somewhat The majority of the individual sites group subjective, assessment of how much, or how themselves conveniently but in some areas little, the geese move around during the there may be a whole chain of islands course of a winter. For example, whereas stretching over 60 or 70 kilometres. In these there can be no justification for splitting the cases an arbitrary 10 km has been chosen as Figure 1. Map showing groupings of Barnacle Goose haunts. Numbering as in Table 1. Barnacle Goose survey 141 Table 1. The numbers of Barnacle Geese Branta leucopsis counted during aerial surveys, 1957-1973 Figures in brackets represent interpolated means of other counts for that site or group. No inter­ polations have been attempted for the February 1957 and March 1959 censuses or for the in­ dividual sites or groups in Ireland in March 1965 (see text). N o. on Region map Site or N o. o f sites Feb M ar D ec M ar A pr M ar M ar M ar (see Table 4) (Figure 1) grouped sites w ith geese in group 1957 1959 1959 1961 1962 1965 1966 1973 E ast C o ast I L am bay Is. 1 45 2 W exford Slobs 1 0 2 Kerry-Clarc 3 Blaskets 2 12 85 0 20 0 4 M agheree Is. 2 0 34 0 0 0 5 Illaunearon 1 0 0 90 60 0 6 M utton Is. 1 6 280 265 3 20 480 Galway-S. Mayo 7 M ac D a ra ’s Is. 1 0 0 0 0 0 43 8 High Is. 8 106 190 140 213 411 53 9 Inishbroon 1 40 40 0 0 0 20 10 Inishdalla 6 40 160 51 86 90 4 11 Clew Bay 3 160 53 150 85 0 0 12 Inishgallon 1 0 50 0 0 40 0 W. and N. Mayo 13 D uvillaun 4 90 30 157 23 156 145 14 Inishkeas 2 1600 1200 2300' 2500' 2800' 2600' 1980' 15 Inishkeeragh 4 190 10 153 188 40 240 16 K id Is. 6 240 152 76 42 164 Sligo Donegal 17 Lissadell 5 363 230 304 370 210 18 Inishduff 2 0 0 35 18 45 19 R athlin 1 10 0 (20) 0 70 20 Toraylaydon 5 90 130 182 262 395 21 Inishdooey 8 30 210 247 309 195 282 22 C lonm ass 1 0 0 50 45 80 0 23 G lash ed y Is. 4 71 107 5 3 14 220 TOTAL IRELAND 69 2327 2771 4164 4424 (4095) 4718 4398 Islay 24 Islay 1 3 000 2800 5500 4800 (8300)2 8500 15000 Inner Hebrides 25 T ro d d ay 1 0 0 18 0 (3) 0 0 26 B rosdale Is. 2 38 140 107 124 (76) 45 0 27 E n. M o r(K in ty re) 1 35 0 14 44 (67) 196 110 28 E n. M o r (Jura) 1 0 10 4 0 (6) 16 (6) 29 O ro n say 1 16 0 0 230 (51) 18 40 30 S oa 1 5 0 0 0 (17) 61 35 31 Treshnish 5 317 299 470 390 510 795 419 32 Tiree 3 420 25 380 484 (301) 354 143 Inner H ebrides 33 Muck 1 19 0 0 2 (5) (5) (5) Outer Hebrides 34 Barra 11 223 49 142 171 289 443 80 35 Sound of Barra 6 238 86 452 415 392 360 336 36South Uist 1 200 110 250 0 23 0 0 37Monachs 3 330 480 519 860 750 1035 640 38 Sound of Harris 20 490 174 599 498 493 575 980 39 T aran say 2 201 15 120 7 0 120 125 40 G askeir 1 41 110 10 70 140 122 0 41 Shiants 3 303 290 214 317 450 483 450 42L. Roag 2 37 0 0 0 52 19 0 43 L. Erisort 2 0 0 0 32 0 6 0 oo © Skye 44Isay 4 151 130 140 395 420 297 45Ascribs 3 193 0 122 204 308 272 132 46 Trodday 4 182 60 108 47 264 236 143 N .