Buller's Albatross Research Articles

Human exploitation assisting a threatened species? The case of muttonbirders and Buller's albatross.

Albatrosses are flexible and adaptable predators, relying on live prey as well as carrion. Use of predictable food sources and reliance on human-produced resources are well-known trait in long-range feeders like albatrosses and petrels. Breeding Buller’s albatrosses studied at Solander I. (Hautere), New Zealand fed their chicks the remains of sooty shearwater juveniles (tītī in Māori), which are harvested from nearby muttonbirding sites. Evidence of this food type was found at over 10% of nests examined, and 17–40% birds that were fitted with GPS loggers visited muttonbirding sites in this and previous studies. Muttonbirding is a traditional practice that has continued for centuries, with up to 120 tonnes of offal discharged to the sea annually during the present day harvest. It coincides with the energetically-demanding early chick period for the albatrosses. Our finding suggests that the offal may be an important, but overlooked element in the albatross diet. As an important supplementary food for the albatrosses it is likely to have contributed to the 3% per annum growth of their populations since the first comprehensive population surveys in 1969.

Modelling the effect of fishing on southern Buller's albatross using a 60-year dataset

Many albatross populations are declining and a major cause is believed to be incidental mortality from fishing. We investigated the effect of fishing on southern Buller's albatross Thalassarche bulleri bulleri, using a new approach to seabird population modelling that allows estimation of demographic parameters from multiple data types. Three types of data were used: a 60-year set of mark–recapture observations, four censuses of the breeding population, and estimates of fishing effort and bycatch. The fisheries risk to the viability of this population over the last 60 years appears to have been small, since the adult population is estimated to have increased about five-fold over that time. There is some cause for concern in recent changes (population growth has slowed, and perhaps reversed, and adult survival rates are falling). The most common age at first breeding was 12 years, and about 80% of adults breed each year. Annual survival was estimated to be 0.91 for juveniles, and varied between this value and 1 for adults. Though this population is not in immediate danger from fishing, there is a need for continued monitoring to see whether the recent fall in survival rates persists and causes a decline in abundance. Our analysis showed that when, as is common, mark–recapture data do not provide good estimates of all demographic rates, the assessment of seabird population trends can be improved by the use of other types of data, particularly abundance.

Natal philopatry does not lead to population genetic differentiation in Buller's albatross (Thalassarche bulleri bulleri)

Genetic variability in the only two existing populations of Buller's albatross (Thalassarche bulleri bulleri) was assessed using six polymorphic microsatellite loci. Large biological samples were obtained from both the Snares (n = 99) and the Solander Islands (n = 27). Several measures of genetic differentiation including F(ST) and R(ST) and a principal coordinates analysis (PCO) suggest a complete absence of genetic structure between three breeding colonies on the Snares Islands, and between them and one breeding colony on the Solander Islands. Mark/recapture studies of recently banded albatross chicks on the Snares found high natal philopatry in T. b. bulleri, but the microsatellite DNA data suggest that sufficient gene flow still occurs between all four breeding colonies to maintain a genetically homogeneous population overall.

Increases in the numbers of breeding pairs in two populations of Buller's Albatross (Thalassarche butteri butteri)

The abundance and distribution of the southern subspecies of Buller's Albatross (Thalassarche b. bulleri) breeding on the Solander and Snares Islands were investigated during February—March 2002. At the Solander Islands, a total of 4912 breeding pairs was estimated from aerial and ground counts. This total compares to an adjusted total of 4147 breeding pairs estimated during February 1996 using the same methods, and indicates average annual increases of 3.1% during the period 1996–2002, compared with relatively stable numbers estimated for the period 1985–96. At the Snares Islands, a total of 8165 breeding pairs was counted on North East Island and associated islets from ground and vantage-point counts, and 8713 breeding pairs were estimated for the Snares Islands as a whole. Analysis of annual counts of breeding pairs on the North Promontory of North East Island showed an estimated increase in the breeding population of 3.2% per year. In 2002, the estimated total breeding population of Buller's Albatross at the Snares and Solander Islands was 13625 pairs.

Variation in the size of Buller's albatross (Thalassarche bulleri) eggs

The effect of minimum maternal experience, individual and year on egg size variation, breeding success and sex of the surviving chick were investigated in Buller's albatrosses (Thalassarche bulleri) breeding at the Snares Islands. Minimum maternal experience and individual effects were studied over the 9 years 1996–2004, while a second set of data allowed inter‐annual variation in egg size to be investigated over 4 additional years (1961, 1969, 1970, and 1993). Egg length, breadth, volume and eccentricity did not vary between years, but all four variables varied significantly between individuals. The size of eggs laid by one individual varied less than the variation across the population as a whole. Egg volume increased with minimum maternal breeding experience, mainly because eggs became broader but not longer, up to the fourth breeding attempt. There was a weak positive relationship between egg size and breeding success, but this correlation was confounded by maternal breeding experience. Breeding success decreased markedly among birds with >20 years breeding experience. There was no relationship between egg size and the sex of the resulting chick. The significant effects of minimum breeding experience and individual on egg size appear to be typical of seabirds. However, unlike other studies of egg size in albatrosses, we did not detect any between‐year effects, perhaps because the experience of the breeding population changed little during the study period.

Simulating the distribution of southern Buller's albatross using an individual‐based population model

Summary A spatially explicit, individual‐based population model (IBPM) for southern Buller's albatross Thalassarche bulleri bulleri was developed to simulate the species’ at‐sea distribution and interactions with fishing fleets. Satellite tracking data for birds from colonies on Snares Islands and Solander Island (south of South Island, New Zealand) suggest that the feeding grounds utilized by a bird, and the duration of its foraging trips, are dependent upon colony, sex, pairing status and developmental stage of egg/chick. These dependencies were incorporated into the IBPM. Simulated distributions were compared with independent shipboard observations by using the IBPM to make replicated ‘virtual counts’ corresponding to each shipboard count. Each shipboard count was assigned a score reflecting the likelihood that a count of this magnitude would have arisen if the true populations behave as described by the IBPM. Randomization tests indicated that, for the months in which we had adequate telemetry data (March–July), predicted and observed distributions were very similar at scales down to 1 degree2. There was some evidence that bird densities around the south‐west corner of New Zealand's South Island were underpredicted in July, and at the scale of individual shipboard counts the ship data showed greater fine‐scale aggregation than the virtual data. Comparison of observed and simulated distributions early in the breeding season (January and February, for which we had no telemetry data) suggested that the foraging behaviour of birds prior to egg laying differs from that exhibited by either breeding or pre‐breeding birds later in the season. Synthesis and applications. In combination with reported by‐catch rates, our IBPM may enable us to derive fishing gear‐specific per‐capita capture rates for Buller's albatross. Our results also emphasize that it may be necessary to represent responses of individual birds encountering vessels at a finer spatiotemporal scale before it will be possible to make robust demographic predictions of the consequences of changes in fishing practices.

Distribution, abundance and behaviour of Buller’s, Chatham Island and Salvin's Albatrosses off Chile and Peru

During 15 cruises between 1980 and 1995, we studied three species of albatross that nest in New Zealand but occur as non‐breeders along the Pacific coast of South America: Buller's Thalassarche bulleri, Chatham Island T. eremita, and Salvin's Albatross T. salvini. We logged 547 h of observation, surveying 7638 km2 of ocean surface, and recorded 86, 27, and 475 individuals, respectively, of the three species. Chatham Island and Salvin's Albatrosses occurred throughout the Humboldt Current, but habitats differed. Buller's and Salvin's Albatrosses preferred the continental slope, while Chatham Island Albatrosses frequented mostly pelagic waters. On a latitudinal basis, Salvin's Albatross distribution was skewed northward in the austral autumn and southward in spring; Chatham Island Albatross occurred southward during autumn, but was everywhere scarce in spring; and Buller's Albatross occurred almost exclusively in the south (30°S to 40°S) in both seasons. Upwelling and wind speed were positively correlated with densities of Buller's and Salvin's Albatrosses. Densities of Chatham Island Albatrosses also were positively correlated with wind speed, but they occurred further offshore in more stratified waters (with less mixing/upwelling) than did the other two. Pelagic population estimates for the Humboldt Current system, analysed using generalized additive models, peaked at 26 700 individuals for Buller's Albatross (95% confidence interval (CI) 13 100–37 100); 6790 for Chatham Island Albatross (CI 3900–11 100); and 133 100 for Salvin's Albatross (CI 82 800–183 600). Based on adult:subadult ratios observed in the study area, our best estimates for the number of wintering adults were 9100, 5800 and 114 400 birds, respectively, or 20%, 73% and 75% of the numbers estimated (44 500, 8000 and 153 300 birds) for the breeding populations at respective colonies. If we subtract from the autumn count the number of adult‐plumaged birds seen in spring (assumed to be non‐breeders), then respective percentages were 0%, 73% and 65%. Foraging locations and attraction by these birds to commercial fishing operations makes them susceptible to mortality as a result of the recent development of a long‐line fishery on the continental slope of Chile.

Diet of southern Buller's albatross (Diomedea bulleri bulleri) and the importance of fishery discards during chick rearing

Southern Buller's albatrosses (Diomedea bulleri bulleri Rothschild) are frequently associated with fishing vessels off southern New Zealand, and may depend substantially on discards from fishing vessels, particularly trawlers, during chick rearing. To test this hypothesis, the diet was determined from 188 chick regurgitations collected at The Snares (May 1996, July 1996 and 1997) and Solander Island (May and July 1997). Fish (mostly discards but also some small species obtained naturally) was the dominant prey category, occurring in 92% of samples, and forming 65% by weight of solid food consumed. Salps (Pyrosoma sp. and lasis zonaria) were the most abundant prey items (44% of all items), and second most important by frequency of occurrence (78%) and weight (24%). Cephalopod remains (mostly arrow squid (Nototodarus spp.) and Histioteuthis atlantica) occurred in 53% of samples, but contributed only 17% by number and 7% by weight. Other dietary items included crustaceans (chiefly Munida gregaria, Nectocarcinus antarctica, and Lepas anatifera), bird feathers, and flotsam. Fishery discards were present in 70% of samples, constituted 60% of the diet by weight, and comprised 91% of the weight of all fish consumed. Discard composition was dominated by Gadiformes (mostly hoki (Macruronus novaezelandiae) and macrourids) in 1996, and by jack mackerel (Trachurus sp.) in 1997. Breeders at The Snares took more discards in July 1997 (68 g per sample) than May or July 1996 (31 and 28 g respectively), those at Solander Island took more in May (56 g) than July 1997 (29 g). In May 1996, the diet of birds at The Snares tended to be biased towards fish (both discards and natural prey) after long foraging trips, but towards cephalopods after short trips. Sexual differences in diet and discard consumption tended to be more pronounced amongst samples from The Snares. The high, and apparently increased proportion of fish in the diet, strongly suggest that discards from fishing operations have a beneficial effect on the population of southern Buller's albatrosses breeding on The Snares.

Population size and trends within the two populations of Southern Buller's Albatross Diomedea bulleri bulleri

The abundance and distribution of Southern Buller's Albatross ( Diomedea bulleri bulleri) were investigated at the Solander Islands in February 1996 and at The Snares in March 1997. The total breeding population of this endemic subspecies was estimated at 11 502 breeding pairs. At the Solander Islands, a total of 2625 occupied nests was estimated from aerial and ground counts in the first accurate census that included all islands in the group. Comparisons with the number of chicks counted on Little Solander Island in 1985 indicated a possible decrease of 18.7% or no change in the numbers of breeding pairs during the period 1985–1996. At The Snares, a total of 8242 occupied nests was counted and a further 635 were estimated on North East Island, Broughton Island, and associated islets and stacks. A comparison with the numbers of occupied nests counted on North East Island, The Snares, during 1969 and 1992 indicated population increases of 78% and 8% during the periods 1969–1992 and 1992–1997, respectively. Differences in the rates of change within The Snares population demonstrate the complexity of population parameters within a single seabird species, thus emphasising the need for careful formulation of conservation measures.

Distribution and movements of Buller's albatross (Diomedea bulleri) in Australasian seas

The distribution and movements of Buller's albatross in Australasian seas are analysed using results of shipborne surveys (13 238 10‐min counts), counts from trawlers, banding data, recoveries on beaches and fishing vessels, and records from the literature. Patterns of marine distribution are documented by monthly accounts and maps. During the breeding season, highest abundances are recorded over shelves and slopes off southern New Zealand (The Snares shelf to 41–43°S off the South Island, D. b. bulleri), around the Chatham Islands and over oceanic subtropical waters east of New Zealand (probably D. b. platei), with marked seasonal variations observed off southern New Zealand. Both subspecies disperse mostly outside Australasian waters during the non‐breeding season. Birds banded on The Snares were recovered off south‐eastern New Zealand (Stewart Island to Cook Strait) and in the eastern tropical Pacific. Immatures accounted for only 0.25% of birds censused during the ship‐borne surveys; they are recorded around the New Zealand mainland in August‐October and February‐May, off south‐eastern Australia and in the Tasman Sea in November‐December, February, and June‐July. Around New Zealand, males predominate among birds recovered along the eastern seaboard, whereas the sex ratio in south‐western waters tends to vary according to water depth and season. Distribution patterns and movements in New Zealand and Australian seas are discussed in relation to breeding events and breeding status.

Reproductive Activity of Force-Paired Cockatiels (Nymphicus hollandicus)

Reproductive Activity of Force-Paired Cockatiels (Nymphicus hollandicus)

BEHAVIOUR OF BLACKBROWED AND GREYHEADED ALBATROSSES AT BIRD ISLAND, SOUTH GEORGIA

Summary Tickell, W. L. N. 1984. Behaviour of Blackbrowed and Greyheaded Albatrosses at Bird Island, South George. Ostrich 55:64-85. The behaviour of Blackbrowed and Greyheaded Albatrosses. Diomedea melanophris and D. chrysostoma, on the breeding grounds at Bird Island, South Georgia are described. Comparisons are made with Buller's Albatross D. bulleri, the Yellownosed Albatross D. chlororhynchos and the Whitecapped Albatross D. cauta. It is concluded that all five species (the mollymauks*) have a basically similar repertoire of displays.

A Census of Buller's Albatross Diomedea Bulleri at the Snares Islands, New Zealand

A Census of Buller's Albatross <i>Diomedea Bulleri</i> at the Snares Islands, New Zealand

Further Occurrences of Buller's Albatross in Australia

Further Occurrences of Buller's Albatross in Australia

Butler's Albatross: An Addition to the Australian List

The first Australian specimen of Buller's Albatross is recorded and notes are given on the identification of the species in the field and in the hand. Ecto- and endoparasites from the specimen are listed.