(222) SKOKHOLM BIRD OBSERVATORY. BY R. M. LOCKLEY, HISTORICAL. THE history of the observatory begins in a rather curious way. It has evolved out of an attempt to farm this remote Pembroke­ shire island by running sheep over its 240 acres of rough grazing, heather, bracken and thrift. As the early details of my discovery of, and decision to live on, the island have already been given in the book Dream Island (1), I need not repeat them here. The island, as I first knew it in 1927, was swarming with rabbits. I employed two men to catch them down, even to exterminate them, if that were possible. If I achieved this extermination I should be in a position to improve the land without fear of spoliation by rabbits, which are notoriously the greatest hindrance to the grass farmer. My rabbit-catchers advocated the extensive use of steel traps, and afterwards, that all the burrows should be dug in. I would not have the latter done, as it was tantamount to a " lock-out " of the thousands of Puffins, Shearwaters and Storm-Petrels which used them in the summer. But I agreed to any other method that did not ruin the homes of these birds. During that first winter I was so busy on repair work at the old buildings on the island that I did not enquire into the procedure adopted by the trappers. I only knew that they were doing fairly well, and that by the end of January they had caught some three thousand rabbits. Occasionally they brought in a Woodcock or Snipe which they said had been caught in the traps. Of the great number of other birds of more inedible kinds which they had caught they were, perhaps, aware of my feelings in the matter, careful to say and show nothing. And I consoled myself that the use of traps, obviously cruel, was justified in this instance as a means to the pastoral life I desired to lead. Two years later the rabbits were proving to me the country belief that " the more you kill them the faster they breed ". This is scientifically true, since the fewer there are the more plentiful the food and the greater the stimulus to breed. And there are no natural mammal enemies in the form of stoat or weasel to check the increase on Skokholm. At the same time my suspicions were aroused as to the number of birds that were being taken daily in the rabbit-traps, and I made a point of visiting these at dawn with the trappers for a few VOL. xxix.] SKOKHOLM BIRD OBSERVATORY. 223 mornings. The result was an unpleasant shock. Thereafter I insisted that everything, alive or dead, that had been trapped, should be brought home with the rabbits each morning. In a few days a formidable list had been compiled. It included Fieldfares, Redwings. Blackbirds, Song-Thrushes, Robins, Stonechats, Meadow- and Rock-Pipits, Sky-Larks, Hedge-Sparrows, Lapwing, Snipe, Woodcock, Water-Rails, Gulls and Little Owls, while so lightly poised were the triggers of the traps, that Wrens, mice and frogs had also been caught. On the day that a Buzzard was caught I determined that traps would never again be used on the island. (We were for­ tunately able to set the broken leg of the Buzzard, and it was healed by the time we released it some ten days later). At first I had told the trappers that traps might only be set in the mouths of rabbit-holes, since I had previously found many illegally set in the open. But this limitation did not check the number of birds caught. The fresh earth covering the traps at the entrances to warrens was just as. attractive to worm-hunting Thrushes, Blackbirds, etc., and in addition many birds,, lacking other refuges, actually went down rabbit burrows for the sake of cover in bad weather and at night. I had by now a thriving flock of sheep on the island, which reached its maximum of one hundred breeding ewes in 1932. However, the determination not to use traps was by then having its effect. The use of snares, ferrets and gas was rather less than half as effective as the abominably efficient steel- traps. The rabbits were gaining each year. In the drought, years of 1933 and 1934 they were as numerous as they had been. in 1927. In fact, by the autumn of 1934, I had to admit defeat or resort to traps again if I wanted to have any grass on which to winter my sheep, of which there were now 200 ewes and lambs. In September, 1934, I hired a barge and a steam tug and removed therein every sheep. The rabbits had won. Although the loss of the sheep as a" source of income was-a serious one, I was in other respects relieved. I argued, perhaps wrongly, that the more I persecuted the rabbits, the more their burrows would fall into disuse, and the less cover there would be for nesting Shearwaters and Puffins. Further, the abundant wild flowers of the island—bluebells, campion, thrift, etc.—were rabbit-proof (by natural selection), but not sheep-proof; the sheep had attacked and trampled these down in the last two years of their occupation. Nevertheless I should have been glad to have been able to exterminate the 224 BRITISH BIRDS. [VOL. XXIX. last rabbit had it been possible. No doubt a new and interesting sheep-proof flora would have sprung up. Sheep-farming would have meant the gradual treading in of the empty rabbit burrows, although it may not necessarily have resulted in the exile of the burrow-nesting sea-birds except, perhaps, on the flat ground. On sloping ground, as at St. Kilda, the presence of such birds with sheep is compatible without the rabbit as architect and excavator. There is no doubt, however, that the absence of an attempt to farm the island within the last forty years has resulted in the present flouiishing state of the sea-bird colonies on Skokholm. From information which I have been able to gather, all pelagic and maritime species were comparatively scarce as breeders at the end of the last century, when the island was under cultivation. Hence my decision—enforced because I would not use steel-traps any longer—to allow the rabbits, and with them the sea-birds, to continue to remain in undisputed possession of the island, was in some ways to me, as a bird-lover, a satisfactory one. Coincident with the erection, in 1933, of the migratory bird trap mentioned below, I had foreseen that the island would be so overrun with rabbits in another twelve months that it would no longer be possible to keep sheep upon it. I was considerably perplexed as to what might be devised for the continuance of the island as a bird-sanctuary if, as seemed likely, work should call me to the mainland when once the sheep had been sold off. And I decided that when that moment came the island should be declared a Bird Observa­ tory where all might come who were interested in the study and preservation of birds, and who were prepared to contribute to the cost of keeping the Observatory in proper running order. In this direction I would acknowledge gratefully the support of the Royal Society for the Protection of Birds, which for a number of years has contributed a sum equal to the lease-rent of the island. I would also place on record my thanks for the interest and concessions extended by the owner of the island, Col. R. V. Lloyd-Philipps, of Dale Castle, Pembrokeshire. ORNITHOLOGICAL WORK. Skokholm, perhaps largely because its lighthouse flashes red at night, does not attract the immense number and variety of migrants, both common and rare, which are recorded at islands where white-flashing lighthouses exist, as at Heligo­ land, Fair Isle, the Isle of May, and Bardsey Island. But in VOL. xxix.] SKOKHOLM BIRD OBSERVATORY. 225 favourable winds it receives its share, perhaps, especially in the spring, of coastal migration. For some time I dallied with the idea of erecting a migratory bird trap on the island to catch some of these passing migrants, following successful experiments in the ringing of sea-birds (2). In 1933, after obtaining the advice of Mr. W. B. Alexander and other ornithologists who had had experience in trapping birds for ringing, I decided to erect in miniature one of the traps of the famous Fanggarten of the Helgoland Vogelwarte. This was done with the manual assistance of my wife and several friends, and a full account of the procedure with plans has already been given in the Countryman (3). The first drive into this trap was made on the evening of August 7th, 1933, and resulted in the capture of five Willow-Warblers. Since that date the following numbers of birds have been caught in the trap:— 1933 1934 1935* No. of days when trapping was attempted ... 53 82 62 Total birds trapped 233 324 346 Total birds ringed ... 175 240 270 No. of birds retrapped 58 84 68 No. of species trapped 19 22 27 Daily average 4.20 3-95 540 No attempt was made to indulge in regular " beating " in the neighbourhood of the garden to induce birds to enter the trap, which was in its experimental stage, and had to prove its worth without these aids, for which I had no time myself. Moreover the cost of rings was a consideration. I had to use them carefully in view of the fact that in the same years the following numbers of rings had been used in ringing sea- birds, and other birds outside the trap :— 1933 1934 1935 874 76of c.