(270) REPORT ON THE "BRITISH BIRDS" CENSUS OF HERONRIES, 1928.* BY E. M. NICHOLSON. PART I. INTRODUCTORY AND HISTORICAL.—The want of satisfactory data regarding the numbers of animals in relation to space and time is an obstacle of which biology is becoming acutely aware. It is clear that until accurate statistics are secured on a sufficient scale research must be restricted, if not actually held up, at a great many points. The small number of observers who are available for any such task, and the obvious difficulties in practice, make it essential at this stage for the object of any national census to be large, conspicuous and easily identified. For such a purpose the Common Heron, Ardea cinerea cinerea, is very nearly ideal. In the British Isles it is a well-known and widely-distributed species, whose breeding-colonies, often protected and of long standing, but rarely of embarassing size, are familiar under the name of heronries. The first attempt to obtain, through the agency of a periodical, information regarding the heronries of Great Britain was made in Vol. I. of The Naturalist as long ago as 1851, when J. Mcintosh sent in a list of 32 sites known to him (28 in England, 3 in Scotland and 1 in Ireland) and made a general appeal for additions. A rather larger catalogue of 33 English sites had already been published by Yarrell (ist Ed., 1843), but the Naturalist list seems to have been compiled quite independently from the start, and is of greater value, since the numerous correspondents whose notes were added during the three succeeding years often knew their sites at first­ hand, and were able to give scraps of contemporary information *EDITOR'S NOTE.—When Mr. Nicholson suggested that BRITISH BIRDS should organize a census of British heronries in England and Wales and, if possible, Scotland, I agreed to do so provided he would not only assist in obtaining the census, but would undertake the great labour of collating the results and preparing the Report. Neither of us fully realized the labour and difficulties involved, but Mr. Nicholson has shirked nothing and has produced a Report which I feel sure will be regarded as a most efficient and masterly exposition of the immense number of facts collected. We are most grateful to Mr. Nicholson for having done this and I take this opportunity of expressing my sincerest thanks, not only to him, but also to every one of those numerous correspondents who have contributed information and made the Report possible.— H.F.W. Map to show the distribution of existing heronries in England and Wales according to their size. The locations of the sites are marked as nearly as possible, but exactness is not claimed. 272 BRITISH BIRDS. (VOL. XXII. about them. This inquiry, though clearly very incomplete, was the basis for the list in Morris's British Birds (1855) which names 71 existing and extinct colonies in England and Wales (some obviously in error) and for the revision of Yarrell (3rd Ed., 1856). In 1872 the late J. E. Harting carried out through the Field, and later the Zoologist, a rather more extensive inquiry, but the standard was not high and little serious verification seems to have been attempted. This primitive census was continued spasmodically into the 'eighties, and was summed up by Saunders in the 4th edition of Yarrell (1884-5). There followed a period prolific in county avifaunas and (after 1900) in volumes of the Victoria County History, which often contain valuable local information about heronries, but no comprehensive inquiry was repeated until Boyd Watt in Scotland (1908) and Frank Bonnett in England (1912) compiled on their own initiative lists of all the sites they could discover. (In Ireland, which is strictly outside the scope of the present census, although several Irish returns have been received, Ussher and Warren's Birds of Ireland (1900) provided a very creditable, though quite incomplete, survey of the Heron population.) During the war it became evident that widespread tree-felling and other factors were dispersing known heronries on an alarming scale, and in three counties efforts were seriously made to enumerate the local heronries, and to ascertain their size. These efforts resulted in the papers of Wiglesworth for Somerset (1918), Blath- wayt for Dorset (1924) and Riviere for Norfolk (1924-5)—the first surveys of any satisfactory accuracy or completeness. In saying this, no disparagement is intended for the pioneers, whose work has a high value so far as it goes, but it must be obvious from the magnitude of the present inquiry, which itself has fallen short of perfection, that the resources at their disposal were quite unequal to the task they set themselves, just as our own resources have proved still unequal to it over a large part of northern Britain. In case this should not be clear a few details will perhaps make it so. ORGANISATION AND ACKNOWLEDGMENTS.—-The census was decided upon in January, 1928, and launched in the February issue of British Birds (antea, Vol. XXL, p. 210). Appeals were also published in the Naturalist, the Field, the Daily Mail and a great many local papers. The response was at first very patchy, and the success of the census remained for some time in doubt, until a number of ornithologists generously undertook to make them­ selves locally responsible, and large areas were thus decentralised. It is certain that if the entire conduct of operations had continued to fall on the central organisation, many local breakdowns could never have been avoided. The organisers have the names VOL. XXII] ORGANISATION & ACKNOWLEDGMENTS. 273 of about 393 persons who have assisted, either by actually counting heronries or by contributing other relevant information, and when allowance is made for the number whose contributions have previously been digested by various local organisers over large areas, it must be reckoned that nearly 500 observers have taken part in the present inquiry. Excluding Scotland, 279 occupied sites have been visited and counted, the majority on more than one occasion, and a further large number of alleged heronries have had to be exhaustively investigated before their non-existence could be proved. The running to earth of an extinct or imaginary colony is equally important with the assessment of an existing one ; in fact the work which has been done in clearing away from the active list the tangle of long-vanished sites and mistaken records must do much to simplify any repetition of the census. It will readily be understood that this Report is indebted to so many people, and for so much, that any elaborate or detailed acknowledgments would allow little space for anything else. Nor is it necessary for the organisers to emphasise how grateful they are for every contribution which has been made towards the attainment of their objective ; the wealth of facts which it is sought to embody in this account is the best tribute possible to the energy, generosity and skill of those who were responsible for securing the material. The names of those known to the compiler of the Report to have supplied information regarding each particular heronry appear in the County Tables against it. To all these, and to those indirect contributors whose names have not reached us, we are very much obliged for their help. Nor must we miss this opportunity of thanking the landowners and tenants, many also unknown to us, who with very rare exceptions readily granted permission to visit the sites, and often put themselves to much trouble to ensure the completeness of the census. It is impossible, however, to refrain from setting on record the names of those observers who saved the census from imminent disaster by undertaking to organise single- handed either counties or whole groups of counties. In England and Wales, which were under the general direction of H. F. Witherby, the counties were organised as follows (roughly from north to south) : Cumberland by Mr. L. E. Hope ; Yorkshire by Mr. Riley Fortune ; Lancashire, Cheshire and Staffordshire (in part) by Mr. A. W. Boyd ; Staffordshire (in part) by Mr. J. R. B. Masefield ; Derbyshire by Mr. A. Roebuck ; Lincolnshire by Capt. J. S. Reeve ; Norfolk by Dr. B. B. Riviere ; Leicester by Mr. W. E. Mayes ; Shropshire and North Wales by Mr. H. E. Forrest ; Monmouth and South Wales by Mr. G. C. S. Ingram ; Hereford, Devon, Cornwall, Dorset and Berkshire by E- M. Nicholson ; Oxfordshire, Buckinghamshire, Wiltshire and Somerset by Mr. 274 BRITISH BIRDS. [VOL. XXII. B. W. Tucker (these last nine partly through the Oxford Ornitho­ logical Society) ; Essex by Mr. W. E. Glegg; London, Middlesex and parts of the Home Counties by the London Natural History Society; and Kent and Sussex by Dr. N. F. Ticehurst. In Scotland Miss L. J. Rintoul and Miss E. V. Baxter had the most difficult and unwieldy task in organising the census. Unfor­ tunately, they found it impossible in the time at their disposal to prevent large areas of the country from being devoid of observers. A considerable amount of material was, however, collected and the work of Mr. W. Duncan, which covered the whole of Dumfries­ shire and Kirkcudbright, Mr. J. Gordon and Mr. E. Richmond Paton in Wigtown, and of Commander G. Hughes-Onslow in Ayrshire should be specially mentioned. The census as a whole however remained very incomplete, and it was felt that an effort should be made to continue it in Scotland in 1929. This we are delighted to be able to say has now been arranged for and Miss Rintoul and Miss Baxter have the promised assistance of Mr.