Heritability of short-scale natal dispersal in a large-scale foraging bird, the wandering albatross

Natal dispersal is a key life history trait for the evolution and adaptation of wild populations. Although its evolution has repeatedly been related to the social and environmental context faced by individuals, parent-offspring regressions have also highlighted a possible heritable component. In this study, we explore heritability of natal dispersal, at the scale of the sub-Antarctic Possession Island, for a large-scale foraging seabird, the Wandering albatross Diomedea exulans, exploiting a pedigree spanning over four decades and a maximum of four generations. The comparison of three different methods shows that heritability on the liability scale can vary drastically depending on the type of model (heritability from 6% to 86%), with a notable underestimation by restricted maximum likelihood animal models (6%) compared to Bayesian animal models (36%). In all cases, however, our results point to significant additive genetic variance in the individual propensity to disperse, after controlling for substantial effects of sex and natal colony. These results reveal promising evolutionary potential for short-scale natal dispersal, which could play a critical role for the long-term persistence of this species on the long run.     

Demographic Responses to Oxidative Stress and Inflammation in the Wandering Albatross (Diomedea exulans)

One of the major challenges in ecological research is the elucidation of physiological mechanisms that underlie the demographic traits of wild animals. We have assessed whether a marker of plasma oxidative stress (TBARS) and plasma haptoglobin (protein of the acute inflammatory phase response) measured at time t predict five demographic parameters (survival rate, return rate to the breeding colony, breeding probability, hatching and fledging success) in sexually mature wandering albatrosses over the next four years (Diomedea exulans) using a five-year individual-based dataset. Non-breeder males, but not females, having higher TBARS at time t had reduced future breeding probabilities; haptoglobin was not related to breeding probability. Neither TBARS nor haptoglobin predicted future hatching or fledging success. Haptoglobin had a marginally positive effect on female survival rate, while TBARS had a marginally negative effect on return rate. Our findings do not support the role for oxidative stress as a constraint of future reproductive success in the albatross. However, our data point to a potential mechanism underlying some aspects of reproductive senescence and survival. Our results also highlight that the study of the consequences of oxidative stress should consider the life-cycle stage of an individual and its reproductive history.     

Extinction in relation to demographic and environmental stochasticity in age-structured models

The demographic variance of an age-structured population is defined. This parameter is further split into components generated by demographic stochasticity in each vital rate. The applicability of these parameters are investigated by checking how an age-structured population process can be approximated by a diffusion with only three parameters. These are the deterministic growth rate computed from the expected projection matrix and the environmental and demographic variances. We also consider age-structured populations where the fecundity at any stage is either zero or one, and there is neither environmental stochasticity nor dependence between individual fecundity and survival. In this case the demographic variance is uniquely determined by the vital rates defining the projection matrix. The demographic variance for a long-lived bird species, the wandering albatross in the southwestern part of the Indian Ocean, is estimated. We also compute estimates of the age-specific contributions to the total demographic variance from survival, fecundity and the covariance between survival and fecundity.     

Poor Transferability of Species Distribution Models for a Pelagic Predator,the Grey Petrel,Indicates Contrasting Habitat Preferences across Ocean Basins

Species distribution models (SDMs) are increasingly applied in conservation management to predict suitable habitat for poorly known populations. High predictive performance of SDMs is evident in validations performed within the model calibration area (interpolation), but few studies have assessed SDM transferability to novel areas (extrapolation), particularly across large spatial scales or pelagic ecosystems. We performed rigorous SDM validation tests on distribution data from three populations of a long-ranging marine predator, the grey petrel Procellaria cinerea, to assess model transferability across the Southern Hemisphere (25-65°S). Oceanographic data were combined with tracks of grey petrels from two remote sub-Antarctic islands (Antipodes and Kerguelen) using boosted regression trees to generate three SDMs: one for each island population, and a combined model. The predictive performance of these models was assessed using withheld tracking data from within the model calibration areas (interpolation), and from a third population, Marion Island (extrapolation). Predictive performance was assessed using k-fold cross validation and point biserial correlation. The two population-specific SDMs included the same predictor variables and suggested birds responded to the same broad-scale oceanographic influences. However, all model validation tests, including of the combined model, determined strong interpolation but weak extrapolation capabilities. These results indicate that habitat use reflects both its availability and bird preferences, such that the realized distribution patterns differ for each population. The spatial predictions by the three SDMs were compared with tracking data and fishing effort to demonstrate the conservation pitfalls of extrapolating SDMs outside calibration regions. This exercise revealed that SDM predictions would have led to an underestimate of overlap with fishing effort and potentially misinformed bycatch mitigation efforts. Although SDMs can elucidate potential distribution patterns relative to large-scale climatic and oceanographic conditions, knowledge of local habitat availability and preferences is necessary to understand and successfully predict region-specific realized distribution patterns.     

Population changes,movements of southern elephant seals on Crozet and Kerguelen Archipelagos in the last decades

Summary The elephant seal populations breeding on the Crozet and Kerguelen Archipelago were surveyed during the eighties. Elephant seals were observed moving between Kerguelen, Amsterdam, Heard Islands and Vestfold Hills and between Crozet and Prince-Edward Archipelagos. No exchanges were observed between Crozet and Kerguelen Archipelagos suggesting that the two populations are more isolated than previously stated. On the Crozet Archipelago, since 1966, the Possession Island population showed at 70% reduction in numbers of cows ashore and the population is still decreasing. On Kerguelen Island there has been a decline of 44% from 1956 to 1989 but the population appears to have stabilized since 1984. It is suggested that elephant seal populations in the Southern Indian Ocean may have been affected by a change at the trophic level over the last four decades. But the highest rate of decrease observed on the Crozet Archipelago and the fact that the population is still decreasing may be explained by additional factors, in particular by killer whale predation.     

Relationship between reversed sexual dimorphism,breeding investment and foraging ecology in a pelagic seabird,the masked booby

Reversed sexual dimorphism (RSD) may be related to different roles in breeding investment and/or foraging, but little information is available on foraging ecology. We studied the foraging behaviour and parental investment by male and female masked boobies, a species with RSD, by combining studies of foraging ecology using miniaturised activity and GPS data loggers of nest attendance, with an experimental study where flight costs were increased. Males attended the chick more often than females, but females provided more food to the chick than males. Males and females foraged during similar periods of the day, had similar prey types and sizes, diving depths, durations of foraging trips, foraging zones and ranges. Females spent a smaller proportion of the foraging trip sitting on the water and had higher diving rate than males, suggesting higher foraging effort by females. In females, trip duration correlated with mass at departure, suggesting a flexible investment through control by body mass. The experimental study showed that handicapped females and female partners of handicapped males lost mass compared to control birds, whereas there was no difference for males. These results indicate that the larger female is the main provisioner of the chick in the pair, and regulates breeding effort in relation to its own body mass, whereas males have a fixed investment. The different breeding investment between the sexes is associated with contrasting foraging strategies, but no clear niche differentiation was observed. The larger size of the females may be advantageous for provisioning the chick with large quantities of energy and for flexible breeding effort, while the smaller male invests in territory defence and nest guarding, a crucial task when breeding at high densities. In masked boobies, division of labour appears to be maximal during chick rearing—the most energy-demanding period—and may be related to evolution of RSD.     

Using stable-isotope analysis of feathers to distinguish moulting and breeding origins of seabirds

To determine whether stable isotope measurements of bird feathers can be used to identify moulting (interbreeding) foraging areas of adult seabirds, we examined the stable-carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopic composition of feathers of chicks and adults of black-browed albatrosses (Diomedea melanophrys) from Kerguelen Islands, southern Indian Ocean. Albatross chicks are fed primarily fish (75% by mass), the diet being dominated by various species of the family Nototheniidae and Channichthyidae which commonly occur in the shelf waters in the vicinity of the colony. δ¹³C and δ¹⁵N values in chick feathers, which are grown in summer in the breeding area, were lower than values in adult feathers, which are grown in winter (δ¹³C: –19.6‰ versus –17.6‰ and δ¹⁵N: 12.4‰ versus 15.7‰, respectively). No differences in δ¹³C and δ¹⁵N values were found in adult wing feathers moulted in 1993 and 1994 and in adult feathers formed at the beginning, middle and end of the 1994 moulting period. These data are consistent with adults moulting in the same area and feeding at the same trophic level from one year to the next and with no major changes in foraging ecology within a given moulting season; they suggest that foraging grounds were different in summer and winter and that these differed in their stable-isotope signature. Changes in both feather δ¹³C and δ¹⁵N values indicated feeding south of the Subtropical Front (STF) during chick rearing, which is in agreement with the known foraging ecology at this time and feeding north of the STF during moult. This, together with band recoveries from adult birds, indicates that black-browed albatrosses from Kerguelen Islands wintered in subtropical waters off southern Australia. The stable-isotope markers in feathers, therefore, have the potential for locating moulting areas of migratory seabird species moving between isotopically distinct regions and for investigating seabirds’ foraging ecology during the poorly known interbreeding period. Such information is needed for studies of year-round ecology of seabirds as well as for their conservation and the long-term monitoring of the pelagic environment. Received: 28 June 1999 / Accepted: 14 September 1999     

Speciation and phylogeography of giant petrels Macronectes

We examine global phylogeography of the two forms of giant petrel Macronectes spp. Although previously considered to be a single taxon, and despite debate over the status of some populations and the existence of minimal genetic data (one mitochondrial cytochrome b sequence per form), the current consensus based on morphology is that there are two species, Northern Giant Petrel M. halli and Southern Giant Petrel M. giganteus. This study examined genetic variation at cytochrome b as well as six microsatellite loci in giant petrels from 22 islands, representing most island groups at which the two species breed. Both markers support separate species status, although sequence divergence in cytochrome b was only 0.42% (corrected). Divergence was estimated to have occurred approximately 0.2 mya, but with some colonies apparently separated for longer (up to 0.5 my). Three clades were found within giant petrels, which separated approximately 0.7 mya, with the Southern Giant Petrel paraphyletic to a monophyletic Northern Giant Petrel. There was evidence of past fragmentation during the Pleistocene, with subsequent secondary contact within Southern Giant Petrels. The analysis also suggested a period of past population expansion that corresponded roughly to the timing of speciation and the separation of an ancestral giant petrel population from the fulmar Fulmarus clade.