Larus Novaehollandiae Research Articles

Silver gull breeding at two colonies in the Sydney-Wollongong regio, Australia

Silver gulls have increased in abundance in Sydney-Wollongong this century. Both the number of colonies and their sizes have grown. The largest colony of 43 000-50000 pairs is on Big I., off Wollongong. Breeding was compared at this colony with that at a satellite colony on artificial structures in Rozelle Bay, Sydney Harbour. Breeding occurred from July to February at Big I., a lengthening of the season since the 1960s. At Rozelle Bay, breeding occurred almost all year round. Egg and clutch size varied within and between years at Big I. First-eggs of clutches, laid during the first breeding peak, were significantly larger than those laid later in each breeding season. The size of third-eggs in clutches differed between years. It is proposed that these disparities were a result of differences in food availability between years. Clutch sizes were significantly larger during the first breeding peak than later clutches of each season. Clutch size was larger at Rozelle Bay. Variation in clutch size was linked to quality of individuals and food availability. Breeding success at colonies was low, indicating that carrying capacities have been reached.

Distribution and Abundance of Seabirds off Phillip Island and within Port Phillip Bay, Victoria, 1986–1988

Seabirds were counted along standard transect routes off Phillip Island and within Port Phillip Bay, Victoria. During these surveys 37 taxa were recognised, although only 10-11 were regularly seen. Of 25 taxa recorded within Port Phillip Bay, 16 were also included in the 28 seen off Phillip Island. Differences between sites related mainly to the occurrence of albatross species off the coast, and the variety of terns seen within Port Phillip. Off Phillip Island, most records were of Short-tailed Shearwater Puffinus tenuirostris which dominated the estimated biomass; in Port Phillip Bay the Silver Gull Larus novaehollandiae was numerically more important though the Australasian Gannet Morus serrator contributed more to the biomass. In general, areas off Phillip Island supported a higher average density and biomass than did those in Port Phillip Bay, primarily due to the seasonal influx of shearwaters during breeding periods. Commoner species, apart from cormorants and shags, were seen to the southem-most ends of transects run off Phillip Island. Main feeding methods are considered and it appears that the species occurring off Phillip Island are essentially polyvorous, taking a range of prey species, whilst most in Port Phillip are piscivorous.

Variation in eggs and the period of rapid yolk deposition of the silver gull Larus novaehollandiae during a protracted laying season

Silver gulls Larus novaehollandiae in south‐western Australia lay eggs over an eight‐month period with peaks in April, July and September. Clutch‐sizes, egg‐sizes and laying‐intervals did not differ between these three peaks, hut second eggs were smaller than first‐laid eggs on each occasion.Rapid yolk deposition took 7–14 days. Daily increments of yolk growth were neither constant nor maternally influenced. The yolks of first‐laid eggs were laid down faster than the yolks of subsequent eggs. Egg size, weight and composition, as well as the period of rapid yolk deposition, may be proximately linked to the age, breeding experience, and body condition of laying females.

Little Eagle Hieraaetus morphnoides Predation of Silver Gulls Larus novaehollandiae at a Colony in South-western Australia

Little Eagle <i>Hieraaetus morphnoides</i> Predation of Silver Gulls <i>Larus novaehollandiae</i> at a Colony in South-western Australia

Partitioning of material discarded from Prawn Trawlers in Morton Bay

Prawn trawlers in Moreton Bay, Queensland, discard about 3000 t of material each year. About 3% floats, and the rest sinks. The floating component is almost entirely fish. At night, floating discards are eaten by silver gulls (Larus novaehollandiae), crested terns (Sterna bergii) and, to a lesser extent, dolphins (Tursiops truncatus). There is little trawling during the day but the last discards are dumped overboard around dawn. At this time cormorants (Phalacrocorax varius) join the scavengers. Birds and dolphins scavenged only fish and cephalopods, and not crustaceans nor echinoderms. Birds are selective as to the size of fish they will eat, but most of the whole fish in the discards are below 50 g, and the largest fish that crested terns ate was 100 g. Dolphins are capable of taking the largest of the discarded fish. Most of the material that sinks is crustaceans (54%) and echinoderms (18%); the rest is elasmo- branchs and rubble. At night, about half of the fish that sink are eaten by diving birds and by dolphins. There was no indication of mid-water scavenging of sinking discards, except for cormorants and dolphins in the upper water column. Approximately 11% of the discards that reach the bottom comprise fish and crustaceans, which are eaten by crabs (Portunus pelagicus) and fish. The remainder- chiefly crabs, echinoderms and elasmobranchs-reach the bottom alive. Altogether, about 20% of discards are eaten by surface and bottom scavengers. Discards are probably important in maintaining populations of the major scavengers.

Reproductive Ecology of Silver Gulls, Larus-Novaehollandiae Stephens, in South-Australia

Aspects of the reproductive ecology of silver gulls, Larus novaehollandiae Stephens, were studied in South Australia during 1968-78. Some 15 950 pulli and 597 breeding adults were banded on 15 colonies, using numbered and coloured leg bands designed for identification of free-living individuals without the necessity of recapture. Nine colonies were on marine islands, four were on lacustrine islands, one was on a port breakwater, and one was on causeways in a saltworks complex. Fidelity to colony, mate and nest-site, and timing of breeding are considered in detail. The spatial relationship of adult and immature gulls, on the colony studied in greatest detail, and reproductive longevity of the gulls are also discussed. The gulls nested from June to December inclusive, although the commencement and length of breeding seasons varied between colonies and between years. There was a marked absence of 1-year-old gulls on breeding colonies. Of 3530 pulli banded on the major study colony, Penguin Island (37�30''S., 140�01''E.) at Beachport, in 1968, 950 were known to be alive in the 1970 breeding season. Almost 40% of these 2-year-olds were seen on breeding colonies, and mostly on the natal colony; however, only 0.3% were known to raise pulli, and a further 0.7% to produce eggs. Significant breeding activity therefore did not commence until the end of the third year, or later. The older, previously established breeders on Penguin Island were significantly more successful, and had significantly earlier laying dates, than younger birds. Potential reproductive longevity appears to be at least 11 breeding seasons. In this study, silver gulls showed considerably less fidelity to nest-sites and colonies than has been suggested previously. Significant shifts of nest-site, or change of colony, with or without the previous mate, were not uncommon. Of gulls banded on nests as established breeding aduls, 7-44% of gulls found breeding in subsequent years were at colonies other than the one where banded. In 1970, over 80% of 2-year-old gulls recorded present on any colony were only recorded on the natal one. Of the pulli banded on Penguin Island in 1968 and 1969 and later found actually nesting or breeding, 18% were recorded on other colonies. A small percentage of gulls were seen to have high fidelity to nest-site and to mate over 3 or 4 seasons, but it is suggested that, for some colonies, over 50% of silver gulls which eventually breed may do so at colonies other than natal. Significant spatial separation was found on Penguin Island between areas generally occupied by established breeders, which were known to be at least 4-year-olds, and by the 2-year-olds. The older birds may select and hold the territories most suitable for nesting, where vegetation or topography minimise intraspecific aggression which often leads to high mortality rates of eggs and pulli, and assist protection of eggs and pulli from extreme weather. Non-breeding gulls associating with the colonies occasionally move into the nesting areas, but are aggressively forced away and tend to congregate on the periphery of the colony or on exposed areas not suitable for successful breeding.

Colony and Nest-Site Selection Behaviour in Silver Gulls &lt;I&gt;Larus novaehollandiae&lt;/I&gt; in Queensland, Australia

Colony and Nest-Site Selection Behaviour in Silver Gulls &lt;I&gt;Larus novaehollandiae&lt;/I&gt; in Queensland, Australia

The Breeding Biology of the Crested Tern Sterna Bergii

SUMMARYLANGHAM, N.P. & K. HULSMAN. 1986. The breeding biology of the Crested Tern Sterna bergii. Emu 86: 23–32. The breeding biology of the Crested Tern Sterna bergii was studied on One Tree Island, Capricornia section of the Great Barrier Reef Marine Park, Australia. The dense nesting habit with its associated adaptations resemble those found in related species of terns. Clutch size was 1.01 with a mean incubation period of 28 days. Laying was spread over 53 days, but individual subcolonies were more synchronised (18 ± 11.5 days). Hatching success in 1979/80 was 69%, most failures being attributed to predation by the Silver Gull Larus novaehollandiae. Smaller subcolonies with proportionally more nests on the perimeter were subjected to greater predation of eggs than were large subcolonies. Overall, there was a decline in hatching success with season. Fledging success was high (85%) with most mortality in 1979/80 being the result of a tropical cyclone. Gulls stole from a third to half of the fish brought to the colony in January 1982. Fledging period varied between 35–43 days. The growth constant (K) was about 0.120, compared with 0.165 for the north temperate Sandwich Tern Sterna sandvicensis. These results are discussed with particular reference to Silver Gull predation.

A revision of the subfamily haplorchinae looss, 1899 (Trematoda: Heterophyidae). III ? Genera Cercarioides and Condylocotyla n.g.

The genus Cercarioides Witenberg, 1929 is redefined from studies on its valid species, C. aharonii Witenberg, 1929 and C. ardeolae Oshmarin, 1970. C. aharonii is redescribed from the single type specimen and from new material from Butorides striatus from Kuala Selangor, Selangor, and Kuala Gula, Perak, West Malaysia, and from Hydroprogne caspia and Larus novaehollandiae from Townsville, Queensland, Australia. C. baylisi Gohar, 1930, C. gonacanthodes Deblock, 1966, and C. orientalis Gu et al., 1979 are reduced to synonymy with C. aharonii. A redescription is given of C. ardeolae from Butorides striatus from Kampung Pueh, First Division, Sarawak; Kuala Selangor, Selangor, West Malaysia; Sungai Menggatal, Kota Kinabalu, Sabah; and Pulau Halang, Riau, Sumatra.

Dispersal of Silver Gulls, Larus novaehollandiae Stephens, from Breeding Colonies in South Australia

Dispersal of Larus novaehollandiae Stephens, from 10 colonies in South Australia, was studied during 1968-8 1 by means of bands designed for identification of free-living, uncaptured individuals. Dispersal patterns were characteristic of each colony, even for three colonies which were, at most, 10 km apart. Almost all dispersal records came from the area between Adelaide and Melbourne, and within 30 km of the coast. After breeding, the majority of gulls disperse eastwards; however, dispersal from each colony was correlated with a shift of gull population into areas where food was available from human sources such as rubbish dumps. From colonies 80 km south-east of Adelaide, a major human population, the predominant winter dispersal of these gulls was north-west, into the city and suburbs. The maximum direct-line dispersal distances recorded for 95% of the 3133 resighted gulls were &lt;458 km. The greatest direct-line distance recorded was 1430 km. Overall, there was no significant difference in the mean dispersal distances of juveniles and adults, although at distances &gt;480 km significantly more juveniles (&lt;2y) were seen than adults (&gt;2y). This involved only 2.5% of the total number of birds resighted. It is suggested that older, dominant birds maintain high status at preferred feeding places, and juveniles are possibly more erratic in their movements, as they search for food. This would account for the difference in the dispersal ofjuveniles and adults from a particular colony, and also for the significantly higher proportion of juveniles found at extreme distances from their natal colonies.

Reproductive Periodicity in a Population of Crested Terns, Sterna bergii Lichtenstein in South Australia

Crested terns breeding in the Fremantle area of south-western Australia nest over an 8-month period, from early April to early November. However, laying is markedly bimodal, with subseasons in autumn and spring. Observations of individually marked breeding crested terns indicated a sedentary population utilizing a number of alternative, traditional colony sites all of which were within the study area. Individual crested terns tended to lay in the same part of the season as in the previous year. Colonies made up of terns with similarly phased reproductive cycles formed at different times within the protracted laying period. Individuals completed only one nesting cycle within a season, remaining in breeding condition for approximately 11-13 weeks. Breeding cycles were broadly circannual but potentially sub-annual. Despite superficial similarities at the populational level, this laying pattern differs markedly from that recorded for the silver gull in the same area. The pattern of breeding shown by crested terns therefore provides a second model to explain the double-nesting phenomenon observed in a number of seabird species on the western Australian coastline.

Selection of Prey and Success of Silver Gulls Robbing Crested Terns

Selection of Prey and Success of Silver Gulls Robbing Crested Terns

Observations on the histology of Austrobilharzia terrigalensis (Trematoda: Schistosomatidae) infection in the silver gull, Larus novaehollandiae

Appleton C. C. 1984. Observations on the histology of Austrobilharzia terrigalensis (Trematoda: Schistosomatidae) infection in the Silver Gull, Larus novaehollandiae. International Journal for Parasitology 14: 23–28. Necropsies were carried out on Silver Gulls, Larus novaehollandiae, naturally infected with the schistosome Austrobilharzia terrigalensis. Adult A. terrigalensis were found in the branches of the meseriteric vein but the liver, lungs and intestine were the organs most affected by the deposition of the parasite's eggs. Descriptions of egg granulomata in these tissues are given and the nature of the damage to the organs is discussed.

Studies on Austrobilharzia terrigalensis (Trematoda: Schistosomatidae) in the swan estuary, Western Australia: Infection in the definitive host, Larus novaehollandiae

The prevalence of Austrobilharzia terrigalensis infection in the Silver Gull ( Larus novaehollandiae) population of the Swan Estuary, Western Australia was shown from autopsies to be 80.7% with a median worm load of five pairs. Maximum egg-output was recorded about 3 weeks after the first eggs were voided in the faeces of experimentally-infected birds. Few worms were thought to live longer than 2–3 months. Egg-output from naturally infected L. novaehollandiae was generally low, with a median rate of 24 eggs/g for birds living within 125 km radius of Perth. The liver, duodenum and small intestine were the organs most heavily involved in A. terrigalensis infection.

Amino-acid sequence of feather keratin from fowl.

The amino acid sequence of a single polypeptide chain, B-4, from fowl feather barbs has been determined. The B-4 chain was found to consist of 96 amino acid residues and to have a molecular weight of 10206 in the S-carboxymethylated form. The N terminus of this protein was an N-acetylserine residue. The B-4 protein contained seven S-carboxymethylcysteine residues, six of which are located in the N-terminal region (residues 1-26), and other one in C terminus. The central region of the peptide chain was rich in hydrophobic residues. There were homologous amino acids at 66 positions in the sequences of the feather keratins of fowl, emu and silver gull. The variation (substitution, deletion and insertion) in sequence was found to be localized in both terminal sections of the polypeptide chain. The B-4 protein structure was predicted to contain beta-sheet (about 30%), turn and random-coil-like structure, and no alpha-helix. beta-Sheet structure is mostly located in the central region (residues 22-70). On the other hand, both terminal regions are almost devoid of secondary structure.

Populations of Little Penguins, Short-Tailed Shearwaters and other Seabirds on Phillip Island, Victoria, 1978

SUMMARYHARRIS, M. P., and K. G. BODE. 1981. Populations of Little Penguins, Short-tailed Shearwaters and other seabirds on Phillip Island, Victoria, 1978. Emu 81: 20–28.The numbers of burrows in colonies of the Short-tailed Shearwater Puffinus tenuirostris and the Little Penguin Eudyptula minor on Phillip Island during October and November 1978 were estimated as 542,300 and in the order of 6,000 respectively. Most (66%) of the Shearwaters' burrows are on Cape Woolamai; almost all the Little Penguins' burrows are at the western end of the Island.Though the number of Shearwater colonies on the Island appears to have increased this century, the total population of Shearwaters may have changed little in recent times. The colonies of both species are being threatened by encroaching real-estate development and increased tourism. Therefore, and because habitats suitable for colonization are unlikely to be available in future, we suggest that reserves should be established or consolidated round the more secure colonies rather than elsewhere.Records of breeding populations of the Silver Gull Larus novaehollandiae, Kelp Gull L. dominicanus and Crested Tern Sterna bergii are also summarized.

Annual Variation in the Clutch and Egg Sizes of Silver Gulls, Larus novaehollandiae

In two seasons following lower than average annual rainfall, silver gulls laid smaller clutches, their eggs were smaller and the sequential decrease in egg volume within a clutch was more pronounced than in a year preceded by heavier rainfall.

The Use of Simple Measurements to Determine the Age of Silver Gull Eggs

The fresh weight of silver gull eggs is closely related to the volume, which is calculable from the length and breadth. Since eggs lose weight at a constant rate during incubation, the density (weight/volume) indicates the duration of incubation. Accuracy of the method was k 2 days in 217 of 250 tests. A curve of age against density is provided.

Multiple Laying by the Silver Gull, Larus novaehollandiae Stephens, on Carnac Island, Western Australia

In 1977 and 1978, silver gulls on Carnac I., near Perth, W.A., bred continuously from March to November, with laying peaks in April, June and August-September. Many pairs laid several times during the year, showing complex patterns of replacement and post-refractory clutches. This prolonged breeding appears to have resulted from sustained predation pressure in an environment with few climatic or food constraints. Intra-clutch egg variation and seasonal changes in clutch and egg sizes followed the patterns common among gulls. Egg sizes in clutches laid by the same individual were very similar, irrespective of time of year.

The isolation of Saumarez Reef virus, a new flavivirus, from bird ticks Ornithodoros capensis and Ixodes eudyptidis in Australia.

Strains of a new flavivirus, for which the name Saumarez Reef Virus is proposed, were isolated from seabird ticks collected from four localities. Two strains were isolated from ticks of the species Ornithodoros capensis Neumann 1901 collected from the nests of Sooty Terns, Sterna fuscata Linnaeus 1766 on coral cays off the east coast of Queensland, Australia. The other three strains were isolated from ticks of the species Ixodes eudyptidis Maskell 1885 taken from two dead Silver Gulls Larus novaehollandiae Stephens 1826 in northern Tasmania. The new virus was compared serologically with 50 other flaviviruses at the Yale Arbovirus Research Unit and was found to be most closely related to Tyuleniy virus.