( 202 ) ON THE NESTING OF THE GULL-BILLED TERN IN THE CAMARGUE.

BY WILLIAM E. GLEGG. THE Gull-billed Tern (Gelochelidon n. nilolica), although not a breeding species, is included in the British list on the strength of some twenty-eight occurrences, which have been recorded in spring or summer chiefly from the east and south of P2ngland. The chief breeding haunts in Europe are the

FOUR NESTS WITH CLUTCHES OF FIVE WERE FOUND. (Photographed by W. E. Glegg.) coasts of Jutland and the Mediterranean countries, as Portugal, Spain, France, Greece and Rumania. In the various descriptions of the breeding distribution of this species the Camargue is invariably included, but on making inquiries as to the definite nesting locality in this district no information was available. In starting on our journey we did so without knowledge that the bird still nested in the Rhone delta. Dr. Eagle Clarke (Ibis, April 1895), although he saw a few at the mouth of the Grand Rhone, did not obtain any evidence of nesting. Mr. Ingram (Field, Sept. 1908) was equally unsuccessful, but probably he was nearer VOL. xvin.] THE GULL-BILLED TERN. 203 the mark as he saw some of these Terns on the western half of the Etang du Valcares, where we had the good fortune to find a large nesting colony. Owing to the number of the islands in this large lagoon it is not easy to say exactly on which of them we found this Ternery on May 20th, 1924, but the position of this particular island may be described as among the most southerly and westerly. It is of some interest that practically all the nesting birds, with the exception of some Common Terns which had taken undis-

NEWLY HATCHED YOUNG OF THE GULL-BILLED TERN. (Photographed by W. E. Glegg.) puted possession of an adjacent tiny islet, were crowded on two small islands separated by about half a mile of water. The bird population of these two islands included Larks, Flamingoes, Red-crested Pochards, Kentish Plovers, Avocets, Gull-billed, Common and Little Terns, and Black- headed Gulls. Very many nests of the different species were found. It is not easy to assign a reason for the pre­ ference shown by the birds to these islands. Protection suggests itself as a possible cause, but there seemed to be 204 BRITISH BIRDS. [VOL. XVHI. few enemies. The Marsh-Harrier is a very common species —my companion finding six nests in one day—but I never saw the Harrier near the islands. On one occasion two Short-eared Owls made their appearance and stayed for some time, but they were the only predatory forms that we

IN THE FULL BLAZE OF THE SUN. (Photographed by W. E. Glegg.) saw among the nesting birds. A few Carrion-Crows might be seen daily near Stes. Maries but they never seemed to go far from the village. These islands, the chosen of the birds, were more or less covered, above high-water mark, with thick vegetation chiefly composed of what, I am informed, CONFIDENTLY SETTLED ON EGGS. (Photographed by W. E. Glegg.) 206 BRITISH BIRDS. [VOL. XVIIT. are Sumda fruticosa and a species of Salicomia. The colony of Gull-billed Terns, which, I estimated, contained seventy to a hundred pairs, was located on the more northerly island, the many nests being crowded together on the north-west corner at the line of demarcation between the mud and the vegetation. Most of the nests were on the mud but many were placed on the open spaces among the bushes. The nesting material, which consisted of bents and shells, varied considerably in amount. The most interesting feature of this colony was the sizes of the clutches, which varied from one to five eggs. Three was undoubtedly the predominating number, but there were many nests with two, a few with one only, four with four, and four with five eggs. I have no reason to think that these larger clutches were the product of more than one bird in each case. I think that this is the first occasion on which clutches of five of the Gull-billed Tern have been recorded and even those of four are unusual. Two to three eggs are generally 'quoted as the normal size of the clutch. Seebohm (British Birds, Vol. III., pp. 265-6}, describing his experiences with a colony of these Terns near Smyrna, where the conditions appear to have been very similar to those in the Camargue, states " The most common number of eggs in each nest was two; three was not uncommon, but we never found four in one clutch." This author also refers to his experiences with a breeding colony of this Tern at Missolonghi, but as he does not refer to the size of the clutch presumably he found nothing new. The idea seems to be gaining ground in the minds of ornithologists that the size of the clutch of a particular species may vary according to district, and a tendency towards larger clutches may be a fixed function of the Gull-billed Terns of the Camargue, but further information is required before a definite conclusion can be formed. In this connexion it must not be forgotten that there is evidence to show that the size of the clutches of a particular Tern colony may vary in some years. It may be added that there appeared to be no tendency towards larger clutches in other species as Avocet, Kentish Plover, Common and Little Tern, all being what might be described as normal. My experience with other species of Tern is that at the nest they are decidedly confiding and speedily become used to the presence of the hide, and so it was with the Tern under consideration. My hide had not been in position thirty minutes when the bird which I desired to photograph was settled on its eggs, and other birds whose nests were still " THE EMBODIMENT OF VIGOROUS ACTIVITY." (Photographed by W. E. Glegg.) 208 BRITISH BIRDS. [VOL. XVIII. closer returned even earlier. On the following day the Tern came on to the nest a few minutes after I entered the tent. The sight from the hide was full of interest and charm as there were many nests at close quarters and the owners, sometimes both sexes, were in close attendance. So many nests under easy observation afforded a good opportunity to learn if both sexes share in the incubation, but although I was in the hide for periods of varying length, on one occasion for as much as five hours, I was unsuccessful in obtaining the necessary evidence. If any change was effected it must have been in the air, but circumstances did not suggest that this was so. Periodically the colony of sitting birds would rise excitedly into the air, almost en masse, without any apparent reason, although it may have been caused by the arrival of a bird with food. The Terns under my notice joined in these general movements, but they never left the nest in such a way as to suggest that a change was being made. If both sexes share in this part of the parental duties, as seems to be the case with most Terns, it may be that the periods are lengthy, or, as in the case of the Black Tern, the major portion may fall to the female. I devoted all possible attention to the question of the food supply, but without much enlightenment. Small fish were brought repeatedly to the Common Terns within my view, but none to the Gull-billed unless it was delivered in the air. Probably most of the food was obtained at some distance from the nesting ground. Very little, if any, fishing seemed to take place in the Etang du Valcares, and the Terns could usually be seen flying seawards and also across the fresh-water etangs, but, although small fish were very numerous in the latter, I have no note of having seen the Terns fishing there. As the water of the etang became shallower, a large stretch of mud near the Ternery was exposed and this was usually the haunt of a number of Gull- billed Terns. Some form of food may have been the attraction. This Tern is as noisy as it is active. It possesses two distinct notes, one of which is an unvarying dissyllable which, to my ear, sounded like " gaa-waak." This note is usually delivered on the wing. The other note may be described as a scolding trisyllable, but not unvaryingly so, for it would be increased to varying lengths. The transliteration of this note I found too difficult, but my description, made while in the hide, gives it as a tittering note repeated more rapidly when getting close to the nest, and, at times, finally VOL. XVIII.] THE GULL-BILLED TERN. 209 developing into a chuckle, Seebohm, in the article already referred to, states that in Greece and Asia Minor, at its breeding colonies, the note reminded him of the laugh of the Herring-Gull, and describes it as " ef, ef, ef," or " af, af, af," but he describes the note heard in the Black Sea as " kay-vek, kay-vek." The birds under my observation, like other species of Tern, never descended far from the nest, very often they dropped to its edge. Many of the attitudes adopted at this stage were the embodiment of vigorous activity, but although very beautiful, yet not reaching the degree of gracefulness of the Common Tern. The primaries of the latter, when the wings are fully raised, point almost vertically, while those of the Gull-billed Tern point little more than hori­ zontally. In this respect the species may be described as intermediate between the Common Tern and the Black- headed Gull. In taking off from the ground the feet of the Gull-billed Tern are instantly brought together. There was not much conflict between the different species, but if a Tern came too near the nest of an Avocet, the rapier- like bill of the latter speedily demonstrated the superiorit}' of its owner. On one occasion a large mixed gathering of Herring- and Black-headed Gulls made its appearance in the colony, but these birds made no attempt to interfere with the Terns. Laying would appear to have started among the Gull- billed Terns almost simultaneously. On June 6th young were found generally throughout the colony, while two days previously not one had been seen. The nestlings have no black on the end of the bill, as in the Common Tern, and I found this a very ready means of distinguishing the young of the two species in the field. During the early days of the life of these young Terns the power of the sun is, no doubt, a serious menace and the shelter, provided by the vegetation of the islands, must materially enhance the chance of success­ ful rearing. As soon as the youngsters have strength they disappear among the bushes. In view of what I have said previously, it may be well to add that other tenantless islands were equally favoured with vegetation. So far as our experiences went (they were limited to the country within walking distance of Stes Maries), the Gull- billed was more numerous than the other three species of Terns, Black, Common and Little, which were identified.