Egg formation and the pre-laying period of Black-browed and Grey-headed Albatrosses Diomedea melanophris and D. chrysostoma at Bird Island, South Georgia

Egg composition and factors influencing egg formation were studied in Black-browed and Grey-headed Albatrosses Diomedea melanophris and D. chrysostoma at Bird Island, South Georgia. At nests where eggs were laid, females arrived 6–7 days after males, stayed one day during which 96% of observed copulations occurred, then departed to sea for c. 16 days in D. chrysostoma, c. 10 days in D. melanophris , returning c. two days before laying. Yolk deposition, however, lasted 21 and 20 days, and started 32 and 29 days before laying, in D. chrysostoma and D. melanophris respectively. Therefore, it is probably initiated by environmental factors not by copulation. Egg, albumen and yolk mass are significantly greater in D. chrysostoma but the proportionate composition of the species' eggs is nearly identical. Reduced differences in chick mass at hatching may reflect the longer incubation period in D. chrysostoma or relate to subsequent differences in chick growth rate.     

Foraging energetics of Grey-headed Albatrosses Diotnedea chrysostoma at Bird Island,South Georgia

At-sea metabolism (CO₂ production) and water turnover of six breeding Grey-headed Albatrosses Diomedea chrysostoma were measured, using the doubly labelled water method, at Bird Island, South Georgia, Mean food consumption (estimated from a water influx rate of 1.01 1 d^-1 and data on dietary composition) was 1200gd^-1 or 50.4 W. At-sea metabolism (derived from a rate of CO₂ production of 3.98 1 h^-1) was 27.7 W, 2.5 times the estimated basal metabolic rate (BMR). On average the birds ingested nearly twice as much food energy as they expended to obtain it. The metabolic rate during flight (estimated from at-sea metabolism and activity budget data) was 36.3 W (range 34.7–39.0 W) or 3.2 (range 3.0–3.4) times the predicted BMR. This is the lowest cost of flight yet measured, but consistent with the highly developed adaptations for economic flight shown by albatrosses. These results are briefly compared with data for other polar vertebrates (penguins, fur seals) exploiting similar prey.     

Moult in Black-browed and Grey-headed Albatrosses Diomedea melanophris and D. chrysostoma

We recorded the age of individual wing and tail feathers of Black-browed and Grey-headed Albatrosses Diomedea melanophris and D. chrysostoma of known age and breeding status at Bird Island, South Georgia. Breeders and non-breeders of both species moult their rectrices annually. Non-breeders moult primaries biennially. In the first year of a cycle, the outer three and some inner primaries are moulted descendantly; in the next year the inner primaries are moulted ascendantly, starting from primary seven. There is a general progression to moulting equal numbers of primaries in each half of the cycle by the time breeding starts at about 10 years of age. Grey-headed Albatrosses usually moult fewer primaries than Black-browed Albatrosses, particularly as 3-year-olds, when they undertake substantial plumage change in body moult. Most secondaries in Black-browed Albatrosses have been replaced once by age 4 years. Breeding Black-browed Albatrosses continue the moult pattern established as immatures whether they fail or not, as do failed Grey-headed Albatrosses. Successful Grey-headed Albatrosses, which breed again 16 months later, moult their three innermost primaries after breeding in the remainder of the current year and, after a period when moult is interrupted, renew the remaining primaries the following year. Comparisons between species and between failed and successful birds within species indicate that moult rate is not closely linked to the length of the interval between breeding attempts. Interspecies differences are better explained by breeding latitude, with tropical albatrosses moulting twice as fast as sub-Antarctic species, possibly reflecting food availability outside the breeding season.     

Foraging energetics of Grey-headed Albatrosses Diotnedea chrysostoma at Bird Island, South Georgia

At-sea metabolism (CO₂ production) and water turnover of six breeding Grey-headed Albatrosses Diomedea chrysostoma were measured, using the doubly labelled water method, at Bird Island, South Georgia, Mean food consumption (estimated from a water influx rate of 1.01 1 d^-1 and data on dietary composition) was 1200gd^-1 or 50.4 W. At-sea metabolism (derived from a rate of CO₂ production of 3.98 1 h^-1) was 27.7 W, 2.5 times the estimated basal metabolic rate (BMR). On average the birds ingested nearly twice as much food energy as they expended to obtain it. The metabolic rate during flight (estimated from at-sea metabolism and activity budget data) was 36.3 W (range 34.7–39.0 W) or 3.2 (range 3.0–3.4) times the predicted BMR. This is the lowest cost of flight yet measured, but consistent with the highly developed adaptations for economic flight shown by albatrosses. These results are briefly compared with data for other polar vertebrates (penguins, fur seals) exploiting similar prey.     

Individual quality and reproductive performance in the Grey-headed Albatross Diomedea chrysostoma

The reproductive performances of Grey-headed Albatrosses Diomedea chrysostoma with a previous record (≤5 years) of consistent success (≤70% chicks fledged from eggs laid—"top" birds) or failure (≤ 70% of attempts failed—"bottom" birds) were compared during 1993 -1995. In 1995, top birds arrived back at the colony significantly earlier, had significantly shorter first and second incubation shifts and hatched larger chicks which grew significantly faster than bottom birds. In 1994, top birds also had larger hatchlings with higher rates of growth than bottom birds. In 1994, top birds had significantly higher hatching, fledging and therefore overall breeding success than bottom birds; very similar trends were evident in 1993 and 1995. Chick-rearing success and all indices of chick growth suggested that food availability was high in 1995 (and 1993) and low in 1994. Therefore the superior performance of top birds was maintained in years of very different conditions, with the chick-rearing period particularly critical. A simple model (using published demographic parameters for Grey-headed Albatrosses on South Georgia) suggests that top birds would produce 2.5 more chicks over their lifetime than bottom birds. With the currently declining population numbers, the relative contribution of top birds to the next generation may be even greater than this.     

Reproductive endocrinology of the Black-browed albatross Diomedea melanophris and the Grey-headed albatross D. chrysostoma

Gonadal size and the circulating concentrations of two pituitary hormones (luteinizing hormone and prolactin) and three gonadal steroids (testosterone, progesterone and oestradiol-17β) were measured in two closely related Diomedea albatrosses at South Georgia. The Grey-headed albatross D. chrysostoma , if successful in rearing a chick, usually breeds biennially, whilst the Black-browed albatross D. melanophris normally breeds annually. Direct examination (by laparoscopy) of the gonads showed that the testes of both species underwent annual cycles, whilst endocrine data confirmed that those male Grey-headed albatrosses at the colony in the pre-laying period but not breeding in that year (having bred successfully the previous year) were apparently in full reproductive condition with elevated testosterone levels typical of breeding birds. However, the females of the two species differed markedly. Grey-headed albatrosses, in a year following successful breeding, had undeveloped ovaries with low levels of circulating oestradiol but high levels of progesterone, whereas the Black-browed albatrosses showed a pattern consistent with annual ovarian development. The profiles of gonadal steroids through the breeding season were similar for the males of both species but differences existed between the females. In the female Grey-headed albatrosses, transient peaks of progesterone were present throughout chick rearing but these were absent from Black-browed albatrosses. Prolactin had a similar profile in both species, with uniformly high levels throughout incubation and a rapid fall near the end of the brood-guard period. It is suggested that Grey-headed, like Black-browed, albatrosses are intrinsically annual breeders. However, if a female Grey-headed albatross breeds successfully in one year, then nutritional factors operate to ensure that in the following year the female does not show ovarian development, although the ovary is active in terms of progesterone secretion.     

Extrapair paternities in black-browed Thalassarche melanophris, grey-headed T. chrysostoma and wandering albatrosses Diomedea exulans at South Georgia

Extrapair paternities (EPP) are relatively common in passerines, but rare in seabirds. Like most seabirds, albatrosses are long lived, form long-term pair bonds and require biparental care for chick-rearing. Microsatellite analyses of 327 chicks from black-browed Thalassarche melanophris , grey-headed T. chrysostoma and wandering albatrosses Diomedea exulans over two breeding seasons revealed the presence of EPP in all three species. Though EPP rates varied between species and years, up to 21% of offspring were the result of extrapair matings. Rates were highest in wandering albatrosses (6–21%) followed by grey-headed (3–10%) and black-browed (0–9%) albatrosses. EPP rates were lower in 1998 compared to 1999 in both black-browed and grey-headed albatrosses, whereas the reverse was true for wandering albatrosses. Interspecific differences in EPP rates may reflect differences in breeding phenology and sexual size dimorphism. Differences in timing and frequency of breeding may promote different opportunities for interactions with birds other than their normal partner. The different breeding habitat, dispersion and mate-attraction rituals in wandering albatross, together with the disparity in size between the sexes may also offer more scope for higher rates of EPP. Despite extensive sampling within each colony, we were unable to identify sires for many of the extrapair young; however males from other colonies were involved, raising interesting questions regarding the timing and nature of such events.     

Influence of adult breeding experience on growth and provisioning of Wandering Albatross Diomedea exulans chicks at South Georgia

For most seabirds, reproductive performance improves with age; in albatrosses this is thought not to be so (experience being acquired before starting breeding) but only one study (of chick growth in a single season at one site) has specifically addressed this. We compared the provisioning performance and growth rates of chicks of Wandering Albatrosses Diomedea exulans breeding for the first (IN), second and third (LE) and fourth or more times (EE) on Bird Island, South Georgia in the austral winters of 1996 and 1997. Eggs from EE adults were significantly heavier than the other two categories and these chicks had a greater mass and longer wings up to 160 days of age and longer culmen and tarsus up to 115 days old. However chicks from all categories fledged at the same average mass, size and age. No significant differences between categories in feeding frequency or meal size were detected but experienced adults made shorter long foraging trips and spent more time at the nest than less experienced birds. Adults that remained at the nest gave chicks smaller meals than those that left immediately after feeding the chick. Although provision of smaller but more frequent meals by experienced adults promotes more rapid chick growth, the resulting differences do not persist into the late chick-rearing period. Our results were very similar to those from Iles Crozet in the Indian Ocean, supporting the hypothesis that when Wandering Albatrosses start to breed they are fully competent foragers but that it takes a while, during early chick-rearing, for birds breeding for the first time to adapt to the additional demands of provisioning a chick.     

Fly or die: the role of fat stores in the growth and development of Grey-headed Albatross Diomedea chrysostoma chicks

Chicks of albatrosses, like other Procellariiformes, become independent at a mass similar to their parents but during growth attain a peak mass some 30% or more greater, before losing mass prior to fledging. The current views are that this high peak mass represents chicks storing fat reserves as an energy sink, or as an insurance against periodic food scarcity, or as a Consequence of natural stochastic variation in provisioning rate. We analysed growth and body composition of Grey‐headed Albatross Diomedea chrysostoma chicks at Bird Island, South Georgia in 1984 and 1986, two years of very different food availability. In 1984 when overall breeding success was only 28% (the lowest in 20 years and less than halt that in 1986), chicks were significantly smaller in terms of peak mass (by 37%), primary length (by 25%), liver, lung, heart and kidney size (by 18–34%) and fat (by 75–80%) but not significantly different in terms of skeletal (tarsus, culmen, ulna, sternum) or muscle (pectoral, leg) size. Despite these differences, there were some important similarities in the patterns of growth in both years. Up to the attainment of peak mass, most of the growth of organs and of skeletal structures was completed and little fat was deposited. In the remaining part of the chick‐rearing period, feather growth and acquisition of fat stores were undertaken. Thus Grey‐headed Albatross chicks begin to acquire substantial fat stores only during the later part of the development period; this is contrary to the predictions of any of the existing hypotheses concerning provisioning patterns and the role of fat stores in Procellariiformes. We propose that the deposition of fat in the later stages of chick growth is an adaptation to: (a) ensure against energy demands and/or nutritional stress affecting the quality of flight feathers (many of which are not renewed for up to three years after fledging); and (b) provide an energy reserve for chicks to use in the critical period immediately after independence.     

Fish prey of the Wandering Albatross Diomedea exulans at South Georgia

Summary The fish diet (45% of total diet by weight) of Wandering Albatrosses rearing chicks at South Georgia during the austral winters of 1983 and 1984 was investigated using otoliths retrieved from regurgitations. These provide the first quantitative data for this species and for any albatross. By number of identified otoliths (32% could be identified only as ?Macrouridae and ?Moridae), Pseudochaenichthys georgianus (35%), Muraenolepis microps (33%) and Chaenocephalus aceratus (20%) predominated, with Notothenia gibberifrons, Pagothenia hansoni and Champsocephalus gunnari (together 12%) also present. Composition by weight (estimated from otolith length) of the main species was Pseudochaenichthys 51%, Muraenolepis 14%, Chaenocephalus 27%; if digestion and wear had reduced otoliths by 10% the values would be Pseudochaenichthys 54%, Chaenocephalus 25%, Muraenolepis 13%. Composition by weight (actual or corrected values) was almost identical between years but epipelagic fish were significantly more abundant in 1983 than 1984. All identified fish eaten by Wandering Albatrosses are common on the South Georgia continental shelf and most of them are caught in the commercial fishery there. However, two of the three main target species of this fishery in 1983–1984, Notothenia rossii and Champsocephalus were not, or rarely, caught by Wandering Albatrosses. It seems unlikely, therefore, that the albatrosses depend greatly on the fishery for acquisition of fish prey but how they catch several species, including Muraenolepis, which are mainly benthic in habit is unknown.     

Population dynamics of Black-browed and Grey-headed Albatrosses Diomedea melanophrys and D. chrysostoma at Campbell Island, New Zealand, 1942–96

The numbers of Black-browed Albatrosses Diomedea melanophrys and Grey-headed Albatrosses D. chrysostoma at Campbell Island, New Zealand, have declined dramatically since the 1940s. Black-browed Albatross numbers went into a steep decline in the 1970s and, since at least 1984, have been increasing slightly at average rates of 1.1% and 2.1% per annum at two colonies. The long-term downward trend in numbers of the Grey-headed Albatross has continued into the 1990s, averaging annually between 3.0% and 4.8% per annum at different colonies. A demographic study carried out between 1984 and 1996 indicates that Black-browed and Grey-headed Albatrosses have similarly high annual adult survival rates (0.945 and 0.953, respectively). Black-browed Albatrosses breed for the first time at a younger average age than do Grey-headed Albatrosses (10 years and 13.5 years, respectively), have a higher average breeding success (0.663 compared with 0.397 for the latter species) and are annual breeders whereas Greyheaded Albatross show a typical biennial pattern of breeding. Both show low survival from fledging to first breeding; averaging 0.186 and 0.162 for Black-browed and Grey-headed Albatrosses, respectively. Both species are accidentally killed in the Japanese long-line fishery for tuna Thunnus sp. in the Australasian region. The steep decline of Black-browed Albatross numbers in the 1970s was concomitant with the development of this fishery in the foraging region of the Campbell Island birds. Currently, the slight increase in numbers is due to high adult survival rates and breeding success, and is coincident with a great reduction in long-line fishing. With stable and high adult survival rates, it is expected that future population trends will be mainly influenced by the recruitment rates. The continuous decline in Grey-headed Albatross numbers since the 1940s, before long-line fishing developed in this region, indicates that natural environmental processes contributed to the downward trend in breeding numbers. Modelling indicates that Grey-headed Albatross numbers will continue to decrease with the present demographic parameters. A comparison between the species breeding at different sites shows that differing environmental conditions influence demographic characteristics.     

Attendance patterns and behaviour in relation to experience and pair-bond formation in the Wandering Albatross Diomedea exulans at South Georgia

Recruitment of Wandering Albatrosses Diomedea exulans to the breeding population at South Georgia took between 2 and 8 years after they first returned to their natal colony. In successive seasons, from first return to pairing, the date of arrival became earlier and the number of days spent ashore and the time spent interacting with other birds increased. Pairing birds arrived earlier and spent more time ashore than birds of similar experience which did not pair in that season. In the season following pairing they returned at the same time as breeding birds, but most did not breed; when ashore they spent much of their time alone or with their partner at the nest site. They left in mid-season before other non-breeders and bred the following season. Some birds accomplished this process by spending much time (50–60 days) ashore in two or three seasons but most birds spent a similar total time ashore spread over more seasons. Until the season prior to breeding, the number of birds of the opposite sex with whom interactions occurred was proportional to the amount of time spent ashore. There was, therefore, considerable scope for inter-individual assessment of potential partners before interactions were confined essentially to a single partner in the season before the first breeding attempt.     

Annual variation in breeding biology of macaroni penguins, Eudyptes chvysolophus, at Bird Island, South Georgia

The breeding biology of the macaroni penguin, Eudyptes chrysolophus , was studied over four years, 1976 and 1986–88, at Bird Island, South Georgia. Birds were migratory, being absent during winter (May to September). Arrival at the colony was highly synchronous between years: 14–23 October, over a 7-year period. The pre-breeding, incubation and chick-brooding period was characterized by long fasts ashore, for 36 and 39 days in males and 41 days in females, alternating with long periods at sea. Within years egg-laying was highly synchronous: 95% of clutches initiated within 4–6 days. Arrival date and mean egg-laying date were later (by 3 days), and breeding population size lower (by 20%) in 1987, compared to other years. The incubation period was 35 days and comprised three long shifts, the first shared by the male and female, the second by the female and the third by the male. In 1986 and 1988 these were of 12, 12 and 9 days' duration, but in 1987 the first shift was significantly shorter: 9 days. Chicks creched at 23–25 days of age and fledged at 60 days of age. Neither chick age nor weight at creching or fledging varied between the years 1986–88. The breeding biology of macaroni penguins at Bird Island is compared with that of other Eudyptes penguins, and with the sympatric gentoo penguin, Pygoscelispupuu. There is little variation in breeding biology within the genus Eudyptes , except in the length of time spent at sea prior to the annual moult. This is much shorter at Bird Island, probably reflecting a greater food availability compared to other localities. Inter-annual variation in certain breeding parameters, e.g. laying date, breeding population size, is much greater in the gentoo penguin than in the macaroni penguin. The shorter breeding season, rearing of only one chick and proportionately lower chick fledging weight in macaroni penguins, may be linked to this species' migratory strategy.     

The fish diet of black-browed albatrossDiomedea melanophris and grey-headed albatrossD. Chrysostoma at South Georgia

 The fish component of the diet of black-browed and grey-headed albatrosses at South Georgia was investigated by intercepting 155 meals from adults arriving to feed chicks during February 1986 and 1994. Fish represented 30% and 72% by mass of the diet of black-browed albatrosses and 14% and 60% by mass of the diet of grey-headed albatrosses in 1986 and 1994 respectively. We determined the identity and quantified the contribution (by numbers, size and mass) of fish species mainly by using otoliths (54 representing 9 taxa and 57 representing 17 taxa in black-browed and grey-headed albatross samples respectively). For black-browed albatrosses in 1986 the main fish prey was Patagonotothen guntheri (77% of otoliths, 51% of estimated fish biomass) and a single large specimen of Icichthys australis (40% estimated biomass), whereas in 1994 Pseudochaenichthys georgianus was the main fish prey (57% of estimated biomass) with Magnisudis prionosa (30%) and Champsocephalus gunnari (12%) also making substantial contributions. Grey-headed albatross samples from 1986 were dominated by southern lampreys (40% by number, 79% of estimated biomass), lanternfish (32% of numbers, 9% by mass) and Patagonotothen guntheri (11% by mass); in 1994 Champsocephalus gunnari (42% by numbers, 24% by mass), Magnisudis prionosa (13% by number, 36% by mass), Muraenolepis microps (90% by number), Pseudochaenichthys georgianus (15% by mass) and lanternfish (18% by number but only 1% by mass) were the main prey. The importance of Patagonotothen guntheri to both species in 1986 and its absence in 1994 probably reflect albatrosses obtaining it from the commercial fishery, which was active in 1986 but closed in 1994. Otherwise the fish diet of black-browed albatrosses is dominated by krill-feeding fish, characteristic of the waters of the South Georgia shelf. In contrast, the grey-headed albatross diet comprises deeper water mesopelagic species, especially lanternfish, which reflect its affinity for the Antarctic Polar Frontal Zone and associated oceanic upwellings. Received: 28 June 1995 / Accepted: 8 October 1995     

Annual variation in breeding biology of gentoo penguins, Pygoscelis papua, at Bird Island, South Georgia

The breeding biology of the gentoo penguin, Pygoscelis papua , was studied over a three-year period (1986–1988) at Bird Island, South Georgia, with particular reference to birds of known age or breeding experience. Laying date varied significantly between all three years, being three weeks later in 1987, when the breeding population decreased markedly. Factors involved in the timing of breeding are discussed. Within years egg-laying was highly synchronous: 95% of clutches were initiated in 14·5 days or less. The incubation period was 35 days and the laying interval, between the two eggs, 3·3–3·4 days. Chicks creched when 25–30 days old, and this varied between years, possibly related to food supply and chick growth. Chicks left the colony for the first time between 75 and 85 days of age. The breeding population at Bird Island decreased by 20% and increased by 84% in successive years during the study period. Breeding success (chicks fledged per egg laid) varied between 0·33 and 0·65 within colonies, but for the whole island was very consistent over the three years: 0·45, 0·51 and 0·47. Overall, colony differences were not correlated between years. Disturbance from Antarctic fur seals, Arctocephalus gazella , is suggested as the cause of consistently lower breeding success at one colony. Mean egg weight varied annually, and with age of the breeding bird, nest location and, in one year, with laying date. Young, first-time breeders laid smaller eggs and had lower breeding success compared to older, experienced birds, similar to other seabirds. However, they differed from other species in laying on average earlier than older birds. The relationship between age, egg weight, laying date and breeding success is discussed in relation to predation and seasonal food supply.     

The use of acoustics to monitor burrow-nesting white-chinned petrels Procellaria aequinoctialis at Bird Island, South Georgia

Tape recordings of two types of vocalisations were used to assess burrow occupancy by white-chinned petrels (Procellaria aequinoctialis) at South Georgia. Birds responded to the rattle call on 74% of occasions and a wheezy call on 85%, with only 10% failing to respond to both calls played one after the other. Occupancy was determined throughout the pre-egg and incubation period and results confirmed what is known about patterns of occupancy by white-chinned petrels. Adults in burrows known to hatch a chick responded on average to 69% of recordings during incubation and less than 10% in only 4% of burrows. Significant inter-site and inter-annual variations in occupancy were recorded, suggesting that this method is sensitive to changes in the number of petrels returning to breed. A sampling protocol for providing population indices for monitoring purposes is recommended. Accepted: 6 March 2000     

Interannual variation in the breeding biology of the Antarctic prion Pachyptila desolata at Bird Island, South Georgia

Interannual variation in aspects of the breeding biology of Antarctic prions was studied for three summers (1989–1992) at Bird island, South Georgia. Egg size, mass and incubation period remained constant. Laying, hatching and fledging were significantly delayed and less synchronous in 1991/92 (range of laying dates 51 days compared to 10–15 days in the two other seasons). This was due to an unusually cold and protracted winter, with ice blocking burrows into the spring, restricting availability of nest sites. Brooding lasted longer in 1991/92 but the overall fledging period was unchanged. Skeletal growth rates did not vary amongst years; growth in mass was slower in 1989/90 but fledging mass was similar in all three years. In 1989/90 and 1991/ 92 later hatched chicks grew (in mass) faster. The survival of chicks from hatching to fledging did not vary amongst years or with hatching date. Feeding frequency was similar between years, once allowance had been made for starlit nights. Thus late and asynchronous breeding in 1991/92 did not result in reduced breeding success either through predation or starvation.
Crustaceans formed 98–99% of the mass of the identifiable portion of regurgitated food samples. Significant annual variation was found within these crustaceans with the presence of krill (least in 1990/91) being inversely related to that of amphipods and copepods. There was no relationship between diet composition and chick growth or survival. Other seabird species, lacking the morphological specialization for feeding on copepods and amphipods, had very low breeding success in 1990/91, when krill was scarce.