Unexpectedly high genetic diversity of mtDNA control region through severe bottleneck in vulnerable albatross <Emphasis Type="Italic">Phoebastria albatrus</Emphasis>

In the late part of the nineteenth century and the early part of the last century, the short-tailed albatross Phoebastria albatrus was in danger of extinction owing to feather hunting. In the middle of the last century, the total number of this species was inferred to be approximately 50–60 with breeding occurring only on Torishima Island of the Izu Islands. Recently, the number of individuals has increased to more than 2,000 and that of their breeding islands to three, namely, Torishima Island, and Minami- and Kita-kojima Islands of the Senkaku Islands. Here, we show that the 44 short-tailed albatrosses we examined represent 29 haplotypes in the control region of mitochondrial DNA, and have a considerably higher genetic diversity than most avian species, but not very high in albatross species; the h and π were 0.96 and 0.013, respectively. However, the parsimony network clearly showed that many intermediate haplotypes were lost. It was concluded that the majority of the haplotypes in the founder population have been maintained. Judging from these findings and the exponential increase in the number of individuals, the present population of the short-tailed albatross seems not to be affected by inbreeding depression through a severe bottleneck. The conservation and expansion of their breeding grounds, and effective protection from bycatch mortality in foraging areas are important for the future survival of this species.     

Use and exploitation of channel waters by the black-browed albatross

Black-browed albatrosses are the most abundant albatross species of the southern hemisphere, breeding on sub-Antarctic and Antarctic oceanic islands around the globe. Their foraging habitat during the breeding season is reasonably well known along its distributional range, indicating a preferred use of waters <500 m deep. The discovery of a colony inserted within the Admiralty Sound, Tierra del Fuego, poses an interesting challenge to the known precepts on foraging behavior for the species. In this study, we present the first record on the foraging distribution of the only known inner-channel colony of albatrosses in the world, using high-resolution GPS loggers. Black-browed albatrosses breeding at the Albatross Islet used exclusively inner-channel waters, at least during the chick-guard stage. Our results indicate a significant smaller foraging range during chick-guard compared with conspecifics from Diego Ramirez and Falklands/Malvinas Islands. Implications for the conservation of this colony are discussed.     

Giant petrels as predators of albatross chicks

Giant petrels Macronectes spp. are not thought to be important predators of albatross chicks, although they are known to kill pre-fledging Thalassarche and Phoebetria albatrosses. We report the first records of predation of healthy great albatross Diomedea spp. chicks, killing wandering albatrosses D. exulans at night on sub-Antarctic Marion Island. Breeding success of this species has decreased markedly in the area where attacks occurred, suggesting that giant petrel predation events are a recent phenomenon. Mouse attacks on wandering albatross chicks may have contributed to the development of this hunting technique. We also report the first observations of giant petrel predation on pre-fledging grey-headed albatross T. chrysostoma chicks as well as additional records of sooty albatross P. fusca chicks being targeted. Only adult northern giant petrels M. halli have been confirmed to kill albatross chicks on Marion Island. Given the threatened status of wandering albatrosses, and the importance of Marion Island for this species, monitoring of their breeding success is necessary to assess whether the predation of chicks by giant petrels spreads around the island.     

Foraging in a changing environment: habitat shifts of an oceanic predator over the last half century

Spatial modelling studies stress the importance of predicting future species distribution in changing environments, but it is also important to establish historical distribution ranges of species to provide baseline conditions for understanding distribution shifts. We focused on pelagic ecosystems, the largest ecosystem on Earth. Based on boosting algorithms, we reconstructed the foraging patterns of an oceanic predator, wandering albatross Diomedea exulans, in the highly dynamic Southern Ocean over the last half century. To access the unobserved past oceanographic conditions, we used simulations of the OPA‐PISCES oceanic model for the 1958–2001 period. Firstly, we validated the simulated oceanographic variables (sea surface temperature and height, wind speed and chlorophyll a) for the 1998–2001 period with remotely sensed oceanographic data, which were highly correlated, except chlorophyll a. Secondly, we developed two habitat models (based on simulated and observed oceanographic variables) describing the foraging probability of albatrosses. We detected no statistically significant differences between the two models and predictions of both models matched the observed distribution patterns reasonably. Finally, we projected the most likely historical key pelagic habitats of albatross for the 1958 to 2001 period and characterised recurrent, occasional and unfavourable foraging areas in a decadal basis based on average predictions and their standard deviations. Our findings 1) provided a historical baseline (1958–1968) of recurrent, occasional and unfavourable foraging habitats, 2) evidenced a progressive habitat shift the following decades driven by a propagation of sea surface height from SE South Africa towards Antarctica from 1958 to 2001 and 3) measured habitat change rates of wandering albatross over the last half century. To our knowledge, our study provides the first quantitative long‐term assessment of the spatial response of a marine top predator to changing pelagic habitats of the Southern Ocean and highlighted the oceanographic mechanisms involved, offering new insights on future effects of climate change on the pelagic realm.     

Environmental heterogeneity and the evolution of foraging behaviour in long ranging greater albatrosses

Habitat selection in heterogeneous environments is assumed to allow diversification. Wide‐ranging species like pelagic seabirds present a paradox, in that their diversity appears difficult to reconcile with a frequent lack of geographical isolation between populations. We studied the foraging strategies of three closely related species of greater albatrosses, wandering albatross, Diomedea exulans, Amsterdam albatrosses D. amsterdamensis and royal albatross, D. epomophora, in relation to environmental heterogeneity at coarse‐grained and fine‐grained scales. During the incubation period the three species foraged at long distances from their colonies. We observed significant differences between the species in the duration of foraging trips and the distance travelled per day. There were significant differences in preference for habitat types in relation to bathymetric features, and in chlorophyll a concentrations in the waters traversed. Royal albatross preferred shallower waters (<1500 m depth), which were rich in chlorophyll (>0.5 mg/m³), while the other species spent on average 80% of their time in waters deeper than this, where chlorophyll levels were lower. Wandering albatrosses foraged in colder waters than Amsterdam albatrosses. Patterns of activity divided the species into two groups: those exploiting oceanic habitats (wandering and Amsterdam albatrosses) spent high proportions of time on the water (49%), and had on average 1.35 takeoffs and landings per hour, while royal albatross, which foraged mainly over neritic waters spent only 35% of their time sitting on the water, and made on average 2.6 takeoff per hour. Further, royal albatross showed a similar pattern of activity during all periods of the day, while wandering and Amsterdam albatrosses were mostly inactive during the night. We link these differences in activity to prey patch availability in two contrasting habitats – continental shelf areas compared to open ocean habitats. The divergent styles of foraging observed in this study suggest that these closely‐related and wide‐ranging species could effectively co‐exist by dividing the resources available to them by different modes of exploitation.     

Distribution of albatross remains in the Far East regions during the Holocene, based on zooarchaeological remains

Many albatross remains have been found in the Japanese Islands and the surrounding areas, such as Sakhalin and South Korea. These remains are interesting for two reasons: numerous sites from which albatross remains have been found are located in coastal regions of the Far East where no albatrosses have been distributed recently, and there are some sites in which albatross remains represent a large portion of avian remains, although albatrosses are not easily preyed upon by human beings. We collected data on albatross remains from archaeological sites in the Far East regions during the Holocene and arranged the remains geographically, temporally and in terms of quantity. Based on these results, we showed that coastal areas along the Seas of Okhotsk and Japan have rarely been used by albatrosses in Modern times, though formerly there were many albatrosses. We proposed two explanations for the shrinkage of their distributional range: excessive hunting in the breeding areas, and distributional changes of prey for albatrosses.     

Documenting the short‐tailed albatross (Phoebastria albatrus) clades historically present in British Columbia,Canada, through ancient DNA analysis of archaeological specimens

The short‐tailed albatross (Phoebastria albatrus) is a threatened seabird whose present‐day range encompasses much of the North Pacific. Within this species, there are two genetic clades (Clades 1 and 2) that have distinctive morphologies and foraging ecologies. Due to a global population collapse in the late 19th and early 20th centuries, the frequency of these clades among the short‐tailed albatross population that historically foraged off British Columbia, Canada, is unclear. To document the species'' historical genetic structure in British Columbia, we applied ancient DNA (aDNA) analysis to 51 archaeological short‐tailed albatross specimens from the Yuquot site (Borden site number: DjSp‐1) that span the past four millennia. We obtained a 141 bp cytochrome b sequence from 43 of the 51 (84.3%) analyzed specimens. Analyses of these sequences indicate 40 of the specimens belong to Clade 1, while 2 belong to Clade 2. We also identified a single specimen with a novel cytochrome b haplotype. Our results indicate that during the past four millennia most of the short‐tailed albatrosses foraging near Yuquot belonged to Clade 1, while individuals from other lineages made more limited use of the area. Comparisons with the results of previous aDNA analyses of archaeological albatrosses from Japanese sites suggest the distribution of Clades 1 and 2 differed. While both albatross clades foraged extensively in the Northwest Pacific, Clade 1 albatrosses appear to have foraged along the west coast of Vancouver Island to a greater extent. Due to their differing distributions, these clades may be exposed to different threats.     

A comprehensive isotopic investigation of habitat preferences in nonbreeding albatrosses from the Southern Ocean

Albatrosses are among the world's most endangered seabirds. Threats during the nonbreeding period have major impacts on their population dynamics, but for most species, detailed information on distribution and ecology remains essentially unknown. We used stable isotope values (δ¹³C and δ¹⁵N) in feathers to infer and compare the moulting (nonbreeding) habitats of 35 populations that include all the 20 species and subspecies (444 individuals) of albatrosses breeding within the Southern Ocean and in fringing subtropical waters. Isotopic values together with a review of available information show that the 20 albatrosses can be categorized into three groups depending on their favoured moulting grounds: 12 (60%) taxa forage primarily in warm neritic waters, six (30%) in northern oceanic waters and two (10%) in oceanic waters of the Southern Ocean. Stable isotopes indicate that habitat preferences during the nonbreeding period vary much less among different breeding populations in some species (wandering, Salvin's, grey‐headed and light‐mantled sooty albatrosses), than others (black‐browed, Indian yellow‐nosed and sooty albatrosses). The major finding of our isotopic investigation is that the great majority of albatrosses spend the nonbreeding period outside the Southern Ocean, with only three species (and in the sooty albatross, just one of the breeding populations) favouring oceanic subantarctic waters at that time. Hence, the study highlights the overwhelming importance of subtropical waters for albatrosses, where the birds are known to interact with human activities and are more likely to be negatively affected by the diverse range of fisheries operating in both neritic and oceanic waters.     

Postnatal dispersal of wandering albatrosses Diomedea exulans: implications for the conservation of the species

Many large marine vertebrates are today threatened by human activities and it is therefore crucial to obtain information on their distribution and behaviour at sea. In particular little is known about the time necessary for juveniles to acquire the foraging skills of adults. We tracked 13 juvenile wandering albatrosses Diomedea exulans by satellite telemetry during their first year at sea. They covered an average distance of 184,000 km during the first year and restricted their dispersal to the unproductive waters of the subtropical Indian Ocean and Tasman Sea. This region of low wind velocities does not overlap with the foraging areas used by adults. After an innate phase of rapid dispersal with a fixed flight direction, young birds progressively increased their daily flight distances and attained adult flight efficiency within their first six months at sea. The complete overlap of the juveniles’ foraging ranges with major long‐line fisheries in the subtropical waters constitutes a major threat that could jeopardize the long term recovery ability of populations of the endangered wandering albatross in the Indian Ocean.     

Differences in the timing and extent of annual moult of black-browed albatrosses Thalassarche melanophris living in contrasting environments

Moult entails costs related to the acquisition of energy and nutrients necessary for feather synthesis, as well as the impact of reduced flight performance induced by gaps in the wing plumage. Variation in moult strategies within and between populations may convey valuable information on energetic trade-offs and other responses to differing environmental constraints. We studied the moult strategies of two populations of a pelagic seabird, the black-browed albatross Thalassarche melanophris, nesting in contrasting environments. According to conventional wisdom, it is exceptional for albatrosses (Diomedeidae) to moult while breeding. Here we show that black-browed albatrosses breeding on the Falklands regularly moult primaries, tail and body feathers during chick-rearing, and the majority of those at South Georgia show some body feather moult in late chick-rearing. The greater moult-breeding overlap at the Falklands allows the birds to annually renew more primary feathers than their counterparts at South Georgia. The results of the present paper, pooled with other evidence, suggest that black-browed albatrosses from South Georgia face a more challenging environment during reproduction. They also serve to warn against the uncritical acceptance of conventional ideas about moult patterns when using feathers to study the ecology of seabirds and other migrants for which there is scant information at particular stages of the annual cycle.     

Annual energy budget and food requirements of breeding wandering albatrosses (<Emphasis Type="Italic">Diomedea exulans</Emphasis>)

Energy budgets form an integral part of our understanding of animal energetics, particularly when presented in the context of reproduction. In this paper, I created a time-energy budget for a breeding pair of wandering albatrosses (Diomedea exulans) to estimate the annual breeding costs and food requirements of the population at Possession Island, Crozet Archipelago. For a breeding cycle that lasts 356 days on average, a pair uses 2,733 MJ to raise a single chick to fledging. This estimate is 1.21 times higher than previously calculated for wandering albatrosses breeding at Marion Island. Unlike the current analysis, the previous study assumed that foraging costs were constant across all stages of the breeding cycle. Recent evidence shows that foraging costs vary during breeding for wandering albatrosses at Crozet and this is probably true for all populations. Incubation costs have also been shown to be substantially lower than previously determined. Therefore, if a wandering albatross pair at Crozet uses a total of 2,733 MJ to breed, they would need to consume at least 1.7 kg bird^–1 day^–1 of fresh food, on average, to balance their own energy requirements and to provision a single chick for approximately 278 days. At this rate of food consumption, the breeding population at Crozet would consume approximately 340 tonnes of fresh food per breeding season.     

The Evangelistas Islets,Chile: a new breeding site for black-browed albatrosses

A previously undescribed population of black-browed albatrosses (Thalassarche melanophrys) is reported at the Evangelistas Islets, Straits of Magellan, Chile. The population was censused from aerial photographs taken on 13 October 2002 that yielded an estimate of the number of breeding pairs. A combined total of 4,670 pairs of black-browed albatrosses were found nesting at Elcano and Lobos Islets, 2 of the 4 islets in the Evangelistas group. This new record raises to four the number of breeding islands of this albatross species in Chile.     

Regulation of foraging trips and incubation routine in male and female wandering albatrosses

The resolution of the conflict between eggcare and foraging was studied in male and female wandering albatrosses. The foraging zone and range, duration of incubation shifts and foraging trips, and associated changes in body mass were studied. Costs during incubation, expressed as the time spent incubating and the proportional loss of body mass, were similar for both sexes. The mass gained at sea was related to the duration of foraging trips, but the relationship was much less significant in males, where foraging ranges, though similar on average to those of females, were very variable. Males foraged in more southerly waters than females, and gained mass more rapidly. Only females appeared to regulate the duration of foraging trips, and this compensated for the mass lost during the incubation fast. Previous breeding experience had no influence on foraging efficiency. Egg desertion because of depletion of body reserves was very rare because birds have a wide safety margin, i.e. the difference between the average body mass when relieved and that at nest desertion. This safety margin enables the birds to compensate for the high variability in the duration of foraging trips, and is probably a reason for the high breeding success of wandering albatrosses. Decisions to return from the sea to the nest or to desert the nest are probably related to the status of body reserves, and have been selected in the large wandering albatross so that both present and future reproductive success are maximised.     

Predator–prey interactions: why do larger albatrosses eat bigger squid?

The relationship between predator sizes and prey sizes is well documented for terrestrial but rarely for marine ecosystems. We show that wandering albatrosses, the biggest albatross species, feed on larger cephalopod prey than those consumed by smaller albatrosses (grey-headed and black-browed albatrosses). This reflects differences in timing of breeding, foraging ecology and their feeding methods. Wandering albatrosses breed later in the year, during the austral winter, than smaller albatrosses (therefore catching older squid) and forage most of the year in Antarctic open waters, sub-Antarctic, subtropical and tropical waters, overlapping minimally with the smaller albatrosses' foraging range while breeding. Also, wandering albatrosses mostly scavenge whereas smaller albatrosses feed more on live prey. Prey ecology may also play a key role because many squid species might experience post-spawning mortality during the austral winter, becoming easily available to wandering albatrosses. Spawning in winter can be linked to predator avoidance (i.e. reduction in mortality in winter by avoiding pelagic predators) and would allow squid larvae to develop and take advantage of the high productivity (i.e. Antarctic phytoplankton bloom) in spring and at the beginning of summer. Thus, aspects of prey and predator ecology may combine to generate observed differences in prey size.     

Seasonal sexual segregation in two Thalassarche albatross species: competitive exclusion,reproductive role specialization or foraging niche divergence?

Sexual segregation by micro- or macrohabitat is common in birds, and usually attributed to size-mediated dominance and exclusion of females by larger males, trophic niche divergence or reproductive role specialization. Our study of black-browed albatrosses, Thalassarche melanophrys, and grey-headed albatrosses, T. chrysostoma, revealed an exceptional degree of sexual segregation during incubation, with largely mutually exclusive core foraging ranges for each sex in both species. Spatial segregation was not apparent during brood-guard or post-guard chick rearing, when adults are constrained to feed close to colonies, providing no evidence for dominance-related competitive exclusion at the macrohabitat level. A comprehensive morphometric comparison indicated considerable species and sexual dimorphism in wing area and wing loading that corresponded, both within and between species, to broad-scale habitat preferences relating to wind strength. We suggest that seasonal sexual segregation in these two species is attributable to niche divergence mediated by differences in flight performance. Such sexual segregation may also have implications for conservation in relation to sex-specific overlap with commercial fisheries.     

Age-Related Variation in Foraging Behaviour in the Wandering Albatross at South Georgia: No Evidence for Senescence

Age-related variation in demographic rates is now widely documented in wild vertebrate systems, and has significant consequences for population and evolutionary dynamics. However, the mechanisms underpinning such variation, particularly in later life, are less well understood. Foraging efficiency is a key determinant of fitness, with implications for individual life history trade-offs. A variety of faculties known to decline in old age, such as muscular function and visual acuity, are likely to influence foraging performance. We examine age-related variation in the foraging behaviour of a long-lived, wide-ranging oceanic seabird, the wandering albatross Diomedea exulans. Using miniaturised tracking technologies, we compared foraging trip characteristics of birds breeding at Bird Island, South Georgia. Based on movement and immersion data collected during the incubation phase of a single breeding season, and from extensive tracking data collected in previous years from different stages of the breeding cycle, we found limited evidence for age-related variation in commonly reported trip parameters, and failed to detect signs of senescent decline. Our results contrast with the limited number of past studies that have examined foraging behaviour in later life, since these have documented changes in performance consistent with senescence. This highlights the importance of studies across different wild animal populations to gain a broader perspective on the processes driving variation in ageing rates.     

Cryptic speciation and population differentiation in the yellow-nosed albatross species complex

The two species of yellow-nosed albatross, Atlantic (Thalassarche chlororhynchos) and Indian (T. carteri), are morphologically similar, but they differ in breeding behaviour and distribution. Both species are listed as endangered by the IUCN due to the limited number of breeding sites, threats from introduced predators and diseases, and impact of commercial fishing. We quantified genetic variation between and within the two species. Using nuclear (microsatellites and two nuclear sequences) and mitochondrial (control region) markers, we analysed 354 samples from four breeding islands (Atlantic: Nightingale, Inaccessible, and Gough; Indian: Amsterdam) and bycatch samples from South Africa and New Zealand. In addition to all markers separating the two species, nuclear markers showed Atlantic yellow-nosed albatrosses from Gough Island are genetically distinct from those breeding at Nightingale and Inaccessible Islands in the Tristan da Cunha archipelago. Nuclear markers confirmed that all bycatch samples were Indian yellow-nosed albatrosses, however, the bycatch birds from South Africa and New Zealand were distinct from each other and from birds breeding on Amsterdam Island, suggesting colony specific dispersal at sea. Our study supports the current recognition of two yellow-nosed albatross species and recognises genetically distinct groups of both Atlantic and Indian yellow-nosed albatross breeding on different islands, which is important for their conservation and management.

     

Inter-annual variability in the breeding performance of seabirds in relation to oceanographic anomalies that affect the Crozet and the Kerguelen sectors of the Southern Ocean

Global warming is expected to increase the frequency and intensity of inter-annual variation in Sea-Surface Temperatures (SST) associated with a latitudinal shift of frontal structures in the Southern Ocean. However, the long-term consequences of these major climatic events on the biotic environment remain poorly understood. We studied the effect of SST anomalies in the southern Indian Ocean on the breeding success of eight seabird species, and found these temperature anomalies to have different effects depending on the foraging habitat of the species. The breeding success of four seabird species foraging mainly south of the Polar Front in Antarctic waters was significantly depressed by warm SST occurring mainly in winter and spring, prior to breeding. Conversely, warm SST anomalies were associated with a higher breeding success for species foraging mainly north of the Polar Front, while no significant effect was found for two species that forage on the Kerguelen plateau. These different responses to changes in the SST were also observed for two closely related species (sooty albatross Phoebetria fusca and light-mantled sooty albatross P. palpebrata ) breeding at Kerguelen. These observations highlight the importance of multi-species long-term monitoring programs for understanding the ecological consequences of environmental variability. Our results suggest that the predicted southward shift of the Polar Front caused by oceanic warming could lead to an important decrease in the breeding performance of top predator seabirds depending on the location and changes of their foraging habitat in relation the Polar Front.     

Dietary segregation of krill-eating South Georgia seabirds

The diets of six of the main seabird species (two petrels, two albatrosses, two penguins) breeding at Bird Island, South Georgia were studied simultaneously during the chick-rearing period in 1986. For five species, Antarctic krill Euphausia superba was the main food (39–98% by mass); grey-headed albatrosses took mainly the ommastrephid squid Martialia hyadesi (71%) and only 16% krill. The size of the krill taken was similar between seabird species, although there were small but significant differences between penguins and the other species. Sex and reproductive status of krill, however, was different between all seabird species, reflecting some combination of differences in foraging ranges, selectivity by predators, or differences in escape responses of krill. For the krill-eating species, the rest of the diet varied substantially between species, comprising Martialia and nototheniid fish (blackbrowed albatross and, along with lanternfish, white-chinned petrel), lanternfish and amphipods (Antarctic prion and macaroni penguin), and icefish (gentoo penguin). Long-term data on breeding success and information on diet in 5–10 other years suggest that in 1986 seabird diet and reproductive performance was indicative of a year of good availability of krill around South Georgia. In such circumstances, ecological segregation between krill-eating species appears to be maintained chiefly by differences in foraging range and feeding methods, which are reviewed. This situation is rather different from the few studies of seabird communities elsewhere, where prey type and size are believed to be the main mechanisms of dietary segregation.     

Mitigating Seabird Bycatch during Hauling by Pelagic Longline Vessels

Bycatch in longline fisheries threatens the viability of some seabird populations. The Hawaii longline swordfish fishery reduced seabird captures by an order of magnitude primarily through mitigating bycatch during setting. Now, 75% of captures occur during hauling. We fit observer data to a generalized additive regression model with mixed effects to determine the significance of the effect of various factors on the standardized seabird haul catch rate. Density of albatrosses attending vessels during hauling, leader length and year had largest model effects. The standardized haul catch rate significantly increased with increased albatross density during hauling. The standardized catch rate was significantly higher the longer the leader: shorter leaders place weighted swivels closer to hooks, reducing the likelihood of baited hooks becoming available to surface-scavenging albatrosses. There was a significant linear increasing temporal trend in the standardized catch rate, possibly partly due to an observed increasing temporal trend in the local abundance of albatrosses attending vessels during hauling. Swivel weight, Beaufort scale and season were also significant but smaller model effects. Most (81%) haul captures were on branchlines actively being retrieved. Future haul mitigation research should therefore focus on reducing bird access to hooks as crew coil branchlines, including methods identified here of shorter leaders and heavier swivels, and other potentially effective methods, including faster branchline coiling and shielding the area where hooks becomes accessible. The proportion of Laysan albatross (Phoebastria immutabilis) captures that occurred during hauling was significantly, 1.6 times, higher than for black-footed albatrosses (P. nigripes), perhaps due to differences in the time of day of foraging and in daytime scavenging competitiveness; mitigating haul bycatch would therefore be a larger benefit to Laysans. Locally, findings identify opportunities to nearly eliminate seabird bycatch. Globally, findings fill a gap in knowledge of methods to mitigate seabird bycatch during pelagic longline hauling.