Australian Breeding Records of the White-Fronted Tern
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AUSTRALIAN 160 BIRD WATCHER More Australian Breeding Records of the White-fronted Tern By J. S. WHINRAY, Flinders Island, Tasmania 7255. In January 1979 some White-fronted Terns Sterna striata Gmelin were found breeding in Tasmania on Battery Island in the Furneaux Group. This New Zealand species was not known to have bred in Australia previously (Whinray 1980, 1981). White-fronted Terns bred on Battery Island in late 1979 and in late 1980. Eggs had been laid there by late October 1981 but, although the rookery had been abandoned by early in December, more eggs were laid later that month. The records for those three seasons are detailed below, and several comments are made on them. Finally some comments are made on the local White-fronted Tern breeding records, distribution, numbers, and clutch size. Battery Island Records 15 December 1979 On this visit I agam found Silver Gulls Larus novaehollandiae, Fairy Terns Sterna nereis, and White-fronted Terns breeding by the summit of the south-eastern point. Except for one nest, the three species again used separate but adjacent nesting areas. The exception was a White-fronted Tern nest separated from the others by the Fairy Tern nests. The gullery started at the southern and south eastern edges of the White-fronted Tern rookery. The latter rookery was larger than in January 1979 and included not only the area used then by the species but also a little of the area used at that time by the Silver Gulls. Thirteen of the fourteen White-fronted Tern nests were shallow depressions in the succulent mat. Three nests had two eggs each and four nests had one egg each. Three nests had two chicks each and three nests had one chick each. The exception was a small shallow depression on the gently sloping granite face around which most of the other White-fronted Tern nests were sited. There was nothing in that nest but the single egg and it was being incubated. All of the chicks were small and none could be banded as their shanks were too thick for bands of the specified size to close around them. The chicks have to be running freely, or be very close to that stage, before their shanks have lengthened and thinned enough to take the bands. Eighteen adults, all of which had full breeding plumage, were at the rookery when I reached it. Adults came and went during the visit; some of the arrivals carried sardine-sized fishes. 29 December 1979 The largest number of adult White-fronted Terns recorded during this visit was eleven and there was no change in their plumage. VOL. 9 (5) MARCH 1982 More Australian Breeding Records of White-fronted Tern 161 Four large chicks, almost large enough to fly, were found by the rookery and banded. Some adults attacked in the usual way as this was being done. Few of the nests seen during the previous visit could be distinguished. The White-fronted Tern that was still incubating had an egg, and its nest was a shallow depression in the succulent mat at the north-eastern part of the rookery. However, as the nests found during the earlier visit were not marked, it was impossible to tell if this were a new nest. Only four more chicks were found. The smallest was still in a nest and another was beside it. The other two were near the south-eastern nest and one of them was just large enough to be banded. No dead chicks were seen at the rookery nor were there any flying immature birds. There could have been considerable mortality since the prior visit. 6 December 1980 White-fronted Terns, Silver Gulls and Fairy Terns were breeding again by the summit of the south-eastern point. All the White-fronted Terns had full breeding plumage and the largest number seen was fourteen. The White-fronted Terns had twelve nests in the usual area, none being separate this year. Three nests had two eggs each, and one nest had two chicks. Three nests had one egg each, three nests had one chick each (one of which had just hatched), and one nest had a hatching egg. The twelfth nest was empty but an adult sat on it each time I left the rookery; perhaps it intended to lay there. In addition there was one chick away from all the nests. Two of the chicks were large enough to be banded but, as that was not anticipated, the bands had not been taken. 25 December 1980 The adult White-fronted Terns still had full breeding plumage, and the largest number counted at the rookery was thirteen. Two of the chicks were able to fly and could not be banded. Eight were banded and only one of those was by a nest. There was one egg in that nest but it Jacked any mark. Although eggs were marked during the last visit, only one might have been done in each nest. However the size of the chick suggested that the nest was one of those recorded during the prior visit. The eggless nest, noted during the prior visit, was still empty and had been abandoned. One nest had a partly hatched chick dead in an egg that had been marked during the same visit. Both it and a hatched egg were collected and given to the Tasmanian Museum (registration number B 3703) . 23 October 1981 Both White-fronted Terns and Fairy Terns had started to Jay by the summit of the south-eastern point. T he former had two nests in the usual area and a third four metres south-east of it, in what had been the gullery in the previous three seasons. The latter nest had two eggs; the others had one egg each. All three nests were marked with numbered metal tags. There was only one Fairy Tern nest. The highest number of White-fronted Terns seen near the rookery was twelve and all were in full breeding plumage. AUSTRALIAN 162 WHINRAY BIRD WATCHER 1 December 1981 As I neared the islet, it was obvious that there were no terns of any sort at the south-eastern point, nor were any White-fronted Terns seen during the visit. The remains of fourteen Silver Gull eggs were collected hurriedly in their usual rookery but fragments encroached into the usual White fronted Tern area by about a metre. All of these eggs appeared to have been broken and eaten when fresh. Small holes, made from the outside, were found in four shells and they seemed the right size-up to 7 mm by 4 mm- to have been made by Silver Gulls. The rock near the broken eggs was cream and white with a heavy coating of bird droppings and that suggested the presence, for some weeks, of a number of birds. 22 December 1981 I steamed near the islet to check it on my way to the far south-east of the Group and was surprised to notice White fronted Terns rising from the south-eastern point. The highest number recorded there was ten, and all were adults in full breeding plumage. Two nests had two eggs each, and two other prepared nests were discernible. Three of these were in the usual area but the other, with eggs, was at the same spot as the isolated nest found on 23 October. The birds usually stay on their nests until one approaches to within about twenty metres, and then return as soon as one moves about that distance away from the rookery. By contrast, on this occasion they left their nests as I landed about seventy metres away and returned to them only after I left the islet. As there was enough time, more pieces of Silver Gull egg shells were collected, and one of them also had a small hole made from the outside. They came from ten eggs, making a total of twenty-four eggs abandoned at the south-eastern point gullery. Of course there could have been more. The 1981 Battery Island Abandonment Falla, Sibson & Turbott (1966) saw the White-fronted Tern's breeding habits as 'Notoriously capricious; a site successfully used one year may not be used the next; or else a few pairs will return, lay a few eggs in a rather desultory way and then abandon the site for the rest of the season'. Soper (1972) gave a less qualified account. He noted that the 'birds have a habit of capriciously changing their breeding sites from one year to the next and even of suddenly deserting a breeding site, for no apparent reason, after eggs have been laid and incubation begun'. Perhaps his account is derived from Falla et al. (1966). By contrast, Oliver (1955) failed to mention abandonment after laying had begun, and made only the general comments that 'Terns do not always continue to nest in the same locality. After a few years in one spot they will change their nesting site. Sometimes they will breed in the same place on alternate years.' With so small a White-fronted Tern population at Battery Island, three nests are a significant proportion of the number of possible nests and so the early abandonment in 1981 seems different from that mentioned by Falla et al. (1966). VOL. 9 (5) MARCH 1982 More Australian Breeding Records of White-fronted Tern 163 When writing of the Silver Gull, Serventy, Serventy & Warham (1971) noted that 'Predation on the eggs and young of other birds is probably mostly a consequence of human interference in sea-bird rookeries'.