Audubon's Shearwater Research Articles

The occurrence and status of black-and-white Puffinus shearwaters on the Kenyan and Tanzanian coasts, with the first specimen records of Persian Shearwater P. persicus persicus

We review specimens and sight records of small black-and-white Puffinus shearwaters in Kenya and Tanzania. An early specimen of an Audubon's Shearwater P. lherminieri sensu lato found inland at Limuru, Kenya in October 1963, long held to represent taxon bailloni (now treated as Tropical Shearwater P. bailloni), is reassigned here to P. b. nicolae. We refer three other specimens and two well-documented sight records to Persian Shearwater P. persicus persicus and a third sight record in northern Tanzania to P. persicus. We suggest that nominate persicus is a regular visitor to the central Kenya coast in December–March, probably as far south as the Pangani region of north-east Tanzania at least, concurrent with a seasonal upwelling event on the Kenya Banks associated with the north-east monsoon. Tropical Shearwater, however, is no more than a rare visitor to East African shores based on current evidence. Our data clarify the status of these shearwaters in the region, provide additional biometric data to complement published sources, and extend the western Indian Ocean non-breeding range of the nominate subspecies of Persian Shearwater approximately 2,000 km south from northern Somalia.

Translocation of mitochondrial DNA into the nuclear genome blurs phylogeographic and conservation genetic studies in seabirds.

Mitochondrial DNA (mtDNA) translocated into the nuclear genome (numt), when co-analysed with genuine mtDNA, could plague phylogeographic studies. To evaluate numt-related biases in population genetics parameters in birds, which are prone to accumulating numts, we targeted the mitochondrial mt-cytb gene. We looked at 13 populations of Audubon's shearwater (Puffinus lherminieri), including five mitochondrial lineages. mt-cytb homologue and paralogue (numt) sequences were determined by Sanger sequencing with and without prior exonuclease digestion of nuclear DNA. Numts formed monophyletic clades corresponding to three of the five mitochondrial lineages tested (the remaining two forming a paraphyletic group). Nineteen percent of numt alleles fell outside of their expected mitochondrial clade, a pattern consistent with multiple translocation events, incomplete lineage sorting (ILS), and/or introgression. When co-analysing mt-cytb paralogues and homologues, excluding individuals with ambiguities underestimates genetic diversity (4%) and differentiation (11%) among least-sampled populations. Removing ambiguous sites drops the proportion of inter-lineage genetic variance by 63%. While co-analysing numts with mitochondrial sequences can lead to severe bias and information loss in bird phylogeographic studies, the separate analysis of genuine mitochondrial loci and their nuclear paralogues can shed light on numt molecular evolution, as well as evolutionary processes such as ILS and introgression.

The use of social attraction techniques to restore seabird colonies on Desecheo Island, Puerto Rico

Abstract Desecheo Island (117 ha) was historically an important seabird island in the Caribbean with 15 species recorded, of which seven are known to breed, including major populations of brown boobies and red‐footed bobbies. The introduction of invasive mammals, plus the use of the island as a bombing range, contributed to the extirpation of five of the seven known breeding populations of seabird species and vastly reduced numbers of the remaining two species. The island became a National Wildlife Refuge in 1976 and major conservation interventions have included the eradication of invasive goats, rhesus macaques and rats between 1976 and 2016. Removing these critical threats from the island has allowed other active restoration goals to be realized, including restoring seabird colonies to the island. Here, we report on the installation of social attraction equipment in 2018 to augment bridled tern and brown noddy colonies and establish a species of conservation concern, the Audubon's shearwater. We supported these actions through a review of historic seabird nesting and roosting on Desecheo. Motion‐sensing cameras were installed to document activity at each social attraction site and evaluate the effectiveness of our methods. During the 2 years of deployment and monitoring, a total of seven bridled tern nests were documented in new and historic sites for the species, two of them next to a decoy colony; however, no brown noddy visits or nests were detected. In 2018 and 2019, one and two Audubon's shearwaters, respectively, were attracted to one of the sound system speakers, representing the first record for this species on the island. Social attraction efforts on Desecheo appears to be a feasible activity that may help support seabird recolonization and support conservation goals for this National Wildlife Refuge.

Phylogenetic Position of Endangered Puffinus lherminieri bannermani

Abstract Puffinus lherminieri bannermani is a small black-and-white shearwater, which is endemic to the Ogasawara Islands, Japan. The taxonomic position of this shearwater is contentious. It is treated as a subspecies of Audubon's Shearwater P. lherminieri or the Tropical Shearwater P. bailloni in some checklists, while it is as considered monotypic, as Bannerman's Shearwater P. bannermani, in others. We examined the mitochondrial cytochrome b region to determine the taxon's phylogenetic position. While on the one hand the results showed that it was not genetically related to either P. lherminieri or P. bailloni, but formed a clade with P. myrtae, P. newelli, and P. auricularis, on the other hand, bannermani has diverged substantially from the other three taxa in both genetic and morphological features. This shearwater was first described as Bannerman's Shearwater, and our results confirm that P. lherminieri bannermani should be split from Audubon's Shearwater, and the monotypic Bannerman's Shearwater is ...

Blanchard Cave 2: A historical period Audubon's shearwater (Puffinus lherminieri) nesting site in Marie-Galante (Guadeloupe islands, FWI)

In this paper we present a natural deposit in Marie-Galante island (French West Indies), Blanchard 2, where historical-period Audubon's shearwater remains dominate the vertebrate assemblage. We combined a study of sediment geometry, a taphonomic analysis of molluscs, crustaceans and vertebrate remains, and direct radiocarbon dating on bird bone to demonstrate that the cave was used as a nesting ground during the island's colonial period. This approach also allows the discussion of the causes leading to the desertion of the site by birds. Finally, we investigate hypotheses regarding the dynamics of Audubon's shearwater nesting during prehistoric and historical times and the impact of anthropogenic phenomenon on these birds.

Some like it hot: effect of environment on population dynamics of a small tropical seabird in the Caribbean region

AbstractAn understanding of how environmental changes affect life history traits and population dynamics is essential for predicting the effects of climate change, managing ecosystems, and determining how species and habitats can best be preserved. This applies particularly to seabirds, which, as top marine predators, are often considered as indicators of marine ecosystem changes. Most studies have so far been conducted in polar or temperate regions. However, important changes in the functioning of tropical marine ecosystems have been reported, but the responses of top predators remain poorly known. This study focused on a tropical seabird, Audubon's shearwater Puffinus lherminieri, analyzing the relationships between climate change and the survival of adults, nesting success, and population dynamics. The population studied breeds in Martinique, in the south of the Caribbean region, which is strongly influenced by the Amazon and Orinoco rivers. A data set for the period 1995 to 2014 was used to estimate the survival by age classes and breeding success and to determine which climate variables most affected demographic parameters. The population dynamics were modeled to predict the future population growth rates in response to climate change. The annual adult survival rate increased over the last 20 years, currently standing at 94% for adult birds more than 6 years old. Adult survival increased with sea surface temperature (SST) during the nonbreeding season as well as with Amazon River discharge, although the latter with a lag of 1 year. The effect of SST was explained by the positive relationship between SST and chlorophyll a during years of high discharge from the Amazon and Orinoco. The population decreased between 1995 and 2007 at a rate of 3% per year and then increased between 2008 and 2014 at a rate of 7% per year. The increase in adult survival observed should continue as temperatures increase in the future, and the population models predicted a stable or increasing population over the next 50 years (λ = 1.018). These results contrast with the negative effect of increasing SST on seabird populations found in temperate and polar regions, emphasizing the need to study the impact of climate change on tropical seabirds.

Current and former populations of Audubon's Shearwater (Puffinus lherminieri) in the Caribbean region

ABSTRACT Cryptic species are often difficult to count and thus protect. Audubon's Shearwater (Puffinus lherminieri) is a cryptic seabird that has disappeared from many colonies, but knowledge of the population's status is incomplete. This paper reviews the survey methods in detail and assesses the status. This species nests or once nested on at least 154 islands in the Caribbean and remains on 137 today, with most habitat just above sea level. Remaining colonies represent 1% of the former breeding area and are remote, with 98 sites lacking any estimate of density. In 16 plots searched on multiple nights using playback, the probability of detection of defended nests was 79 ± 5% (57 of 72 defended nests) in a single night of searching. Pairs were attempting to breed in 54 ± 6% (39 of 72) of defended nests. Average densities, adjusted for missed detections, ranged from 0.6 to 246 defended nests ha−1 (n = 21 colonies, median = 18.5 ha−1, area-weighted mean = 104 ha−1). Using the best data from every colony, a...

Breeding seabird populations in Brazilian oceanic islands: historical review, update and a call for census standardization

In recent decades, several seabird populations have declined globally due to anthropogenic activities. In Brazil, 14 seabird species breed at four oceanic islands and one atoll: the Abrolhos, Fernando de Noronha, and Sao Pedro and Sao Paulo (SPSPA) archipelagos; the Trindade/Martin Vaz Islands; and the Atol das Rocas. Seven species are listed as nationally threatened by extinction. This study aimed to present new information on breeding seabird populations in Brazilian oceanic islands, compile all available data previously published and, when possible, to provide updated information on population estimates from censuses carried out sporadically at different islands between 2006 and 2013. Based on new data and the thorough review provided here, of the 35 seabird breeding populations analysed, 14% were increasing (as Red-billed Tropicbird Phaethon aethereus , Magnificent Frigatebird Fregata magnificens and Brown Noddy Anous stolidus in Abrolhos), 11% were decreasing (as Brown Booby Sula leucogaster in Atol das Rocas and Great Frigatebird Fregata minor in Trindade Island), 23% were stable (as White-tailed Tropicbird Phaethon lepturus in Fernando de Noronha and Brown Noddy and Black Noddy Anous minutus in Sao Pedro and Sao Paulo Archipelago), and the remaining 49% were unknown or not possible to evaluate. The Red-footed Booby ( Sula sula ) is locally extinct in Trindade Island, however there are colonies of only a few individuals of other species, such as the Audubon's Shearwater Puffinus lherminieri and Red- billed Tropicbird in Noronha, Black Noddy in Martin Vaz, and Great ( Fregata ariel trinitatis ) and Lesser ( F. m. nicoll i) Frigatebirds in Trindade, that may become extinct soon. Censuses at distinct periods of the breeding cycles and protocols were highly variable, making temporal comparisons difficult. These results indicate an urgent need for long-term studies to improve the scenario to assess seabird population trends based on comparable methodologies, in order to determine trends in the future.

Seabirds of the Cay Sal Bank, The Bahamas

Abstract. The Cay Sal Bank in The Bahamas is one of the Caribbean region's most important areas for breeding seabirds, but the colonies previously lacked solid estimates. This paper describes results of four visits between 2010 and 2012. The Santaren Channel, used to transit to and from Cay Sal Bank, contained high numbers (6.1 ± 0.4 birds per km2) of seabirds. The Cay Say Bank has at least 117 detectable islands with 484 ha of land area; the most numerous colony was at Elbow Cay (23 ha). Audubon's Shearwaters (Puffinus lherminieri) were breeding at 97 pairs per ha (total: 2,200; 95% CI = 1,650–2,800 pairs), Sooty Terns (Onychoprion fuscatus) at 382 pairs per ha (total: 8,800; 95% CI = 6,900–10,700 pairs), Bridled Terns (Onychoprion anaethetus) at 38 pairs per km coastline (5,829 m coastline; total: 220; 95% CI = 145–295 pairs) and Brown Noddies (Anous stolidus) at 72 pairs per ha (total: 1,609; 95% CI = 1,070–2,250 pairs). The population of Audubon's Shearwaters is among the largest in the world while po...

Potential geographic distribution and conservation of Audubon's Shearwater, Puffinus lherminieri in Brazil

Audubon's Shearwater (Puffinus lherminieri Lesson 1839) is a tropical seabird occurring mainly between southern Canada and the southeast coast of Brazil. Puffinus lherminieri is considered Critically Endangered on the Brazilian Red List because it only occurs in two known localities, both of which contain very small populations. However, many offshore islands along the Brazilian coast are poorly known and the discovery of new colonies would be of considerable significance for the conservation of this species. The aim of this study was to estimate the potential geographic distribution of Audubon's Shearwater in Brazil, based on ecological niche model (ENM) using Maxent algorithm with layers obtained from AquaMaps environmental dataset. The ENM was based on 37 records for reproduction areas in North and South America. The model yielded a very broad potential distribution, covering most of the Atlantic coast ranging from Brazil to the US. When filtered for islands along the Brazilian coast, the model indicates higher levels of environmental suitability near the states of São Paulo, Rio de Janeiro, Espírito Santo and Bahia. However, P. lherminieri prefers islands in environments with warm saline water. Thus, based on the influence of currents that act on the Brazilian coast we can infer undiscovered colonies are most likely to occur on islands on coast of Bahia, Espírito Santo and extreme north of the Rio de Janeiro. These should be intensively surveyed while the islands south of Cabo Frio should be discarded. The existence of new populations would have profound effects on the conservation status of this enigmatic and rarely seen seabird.

A nomenclatural history of Audubon's Shearwater with designation of a neotype forPuffinus lherminieriLesson, 1839 (Aves: Procellariidae)

The nomenclatural history of the small Antillean species that now goes by the name Audubon's Shearwater Puffinus lherminieri is briefly summarized. The type material of Puffinus lherminieri Lesson, 1839, supposed to be in a museum in Rochefort, France, could not be located and is presumed lost. The stated type locality “ad ripas Antillarum” is so general as to encompass almost the entire breeding range of the species, which is widely distributed in the Antillean region and has been regarded as showing variation meriting subspecific designation. Although the type locality was apparently legitimately restricted to Guadeloupe in 1948 or earlier, it was elsewhere erroneously restricted to “Straits of Florida” from 1931 to 1998 and up to the present. To resolve these numerous conflicts and uncertainties, a neotype collected in Saint Barthélemy, once administratively part of Guadeloupe, is here designated.

Foraging over Sargassum by Western North Atlantic Seabirds

Drifting reefs of Sargassum (a brown alga) are used by a variety of pelagic seabirds in the western Atlantic Ocean. We examined gut contents from 964 individuals of 39 seabird species collected 5 to 60 km off the coast of North Carolina for evidence of Sargassum use. Sargassum pieces or Sargassum-associated prey were found in nine of 10 Procellariiformes species and less frequently among Charadriiformes (12 of 25 species). No Sargassum-associated prey was found in Pelecaniformes examined, but observational data indicated that Atlantic tropicbirds (Phaethon lepturus and P. aethereus) and Masked Boobies (Sula dactylatra) commonly foraged over Sargassum. Four species were considered Sargassum specialists, having frequencies of occurrence >25% and high volumes of Sargassum-associated prey: Audubon's Shearwater (Puffinus lherminieri), Royal Tern (Thalasseus maximus), Bridled Tern (Onychoprion anaethetus), and Red-necked Phalarope (Phalaropus lobatus). Seven species fed in Sargassum to a lesser extent, and nine species had ingested Sargassum pieces, but contained no Sargassum-associated prey. It is likely that other seabird species forage regularly over Sargassum, as our conclusions are based on relatively small sample sizes taken during random sampling in the open ocean. Our conservative analysis and extensive observational data indicate the Sargassum community is critical for feeding for some western North Atlantic seabirds. Degradation of Sargassum habitats by oil development, harvest, and/or ocean acidification would undoubtedly have negative effects on fitness of these birds.

A New Species of Shearwater (Puffinus) Recorded from Midway Atoll, Northwestern Hawaiian Islands

Abstract. Small black-and-white shearwaters of the genus Puffinus are distributed globally, and their phylogenetic relationships are complex and uncertain. In 1963 a small shearwater collected at Midway Atoll in the North Pacific Ocean was identified as a Little Shearwater (P. assimilis), but several physical features suggest closer alliance with Audubon's Shearwater (P. lherminieri) and its relatives. Biometrics indicate that the taxon this specimen represents is smaller than any other known shearwater, and phylogenetic analyses indicate it is distinct, with a pair-wise sequence divergence of at least 3.8% from related taxa. We thus propose a new species based on the specimen: Bryan's Shearwater (Puffinus bryani nom. nov.). The breeding and nonbreeding ranges of Bryan's Shearwater are unknown, but a physical resemblance to the North Atlantic boydi (of controversial taxonomic status within Puffinus) suggests an affiliation with subtropical or tropical waters. Bryan's Shearwater is apparently rare and coul...

Quaternary Intertidal Deposits Intercalated with Volcanic Rocks on Isla Sombrero Chino in the Galápagos Islands (Ecuador)

A stratigraphic succession composed of limestone intercalated with volcanic ash and basalt capped by a conglomerate of mixed limestone and basalt cobbles was deposited in a trough-shaped depression approximately 25 m wide and 50 m long to a thickness of 1.62 m on the southwest side of Isla Sombrero Chino in the Galápagos Islands of Ecuador. Two layers of well-cemented calcarenite up to 20 cm thick accumulated as beach deposits with bioclasts of gastropods dominated by the Galápagos Periwinkle (Nodilittorina galapagiensis), a representative of the Beaded Hoofshell (Hipponix grayanus), broken crab fragments, and bird bones. Crustacean remains most likely belong to the Sally Lightfoot Crab (Graspus graspus). The bird bones are attributed to Audubon's Shearwater (Puffinus iherminieri). Distinctly intertidal in origin, such a mixed assemblage of invertebrates and vertebrates is unusual, and the association with basalt flows is seldom met in the rock record. The pristine state of the volcanic cone on Sombrero Chino is consistent with a 3He exposure age of 13 ± 0.8 ka. The age of the basalt-limestone sequence is unknown but must be younger than the 3He exposure age. The basalt-limestone sequence is elevated approximately 3 to 4 m above current sea level. This implies that the intertidal limestone was deposited during an interval of higher sea level or, more likely, was uplifted by magmatic inflation. Such intertidal deposits, in conjunction with more precise dating, have the potential to constrain the history of relative sea-level change during island growth and isostatic subsidence related to volcanism and lithospheric cooling. Intertidal deposits of the kind reported here also help to distinguish between monogenetic as opposed to polygenetic history for volcanic islands.

Mercury levels in the feathers of breeding seabirds in the Seychelles, western Indian Ocean, from 1996 to 2005

We analysed mercury levels in the breast feathers of several breeding seabirds—White-tailed Tropicbird (Phaethon lepturus), Audubon's Shearwater(Puffinus lherminieri), Lesser Noddy (Anous tenuirostris), White Tern (Gygis alba), Sooty Tern (Onychoprion fuscata) and Roseate Tern (Sterna dougallii)—on Aride Island in the Seychelles during three periods between 1996 and 2005. Mercury concentrations tended to be higher in the second sampling period (2002–03) than the first (1996–97), particularly for inshore-feeding species. El Niño events in 1997–99 and 2002–03 might help to explain this pattern, through an increase in mercury bioavailability for seabirds that forage inshore. However, levels of mercury in tissue decreased significantly from the first period (1996–97) to the third period (2004–05) for inshore-foraging species (Lesser Noddy mean ± s.e.: 0.82 ± 0.02 mg g−1 v. 0.53 ± 0.06 μg g−1 respectively) and more wide-ranging, offshore-feeding species (Sooty Tern: 1.16–0.05 v. 0.59 ± 0.04; White-tailed Tropicbird: 1.82 ± 0.05 v. 1.43 ± 0.09). Wide-ranging species of seabirds are more likely to be useful bioindicators at large spatial scales, with such species suggesting a decreasing trend in mercury pollution in the western Indian Ocean.

Comparative foraging ecology of a tropical seabird community of the Seychelles, western Indian Ocean

We studied the foraging ecology of a tropical seabird community in 2 islands of the Seychelles from 2005 to 2007. Chick dietary samples were used to compare feeding habits among species and assess inter-annual and seasonal variations in diet. Fish prey dominated the diet of the community (68 to 100%, of prey consumed), although cephalopods were present in 61.3, 40.0, 27.1 and 32.9% of the food samples from white-tailed tropicbirds, sooty terns, brown noddies and wedge-tailed shearwaters, respectively. We found high diet overlap between species (Mullidae fish being the first prey consumed [30 to 90%] for all species except for the white-tailed tropicbird [\textless2%]) but some segregation in prey length. Other important prey were Exocoetidae, Carangidae, Scombridae and Clupeidae mainly for white-tailed tropicbirds, sooty terns and brown noddies, Hemiramphidae and Coryphaenidae for white-tailed tropicbirds, and Engraulidae and fish larvae for lesser noddies and Audubon's shearwaters. Despise some inter-annual and seasonal variations in diet, these were not consistent within the community. Responses of the seabird community to an environmental perturbation that negatively affected chick growth and breeding success of lesser noddies emphasised the higher vulnerability of species with smaller foraging ranges and/or with lower ability to switch diet (lesser noddy, roseate tern) compared to less range-restricted and/or more opportunistic ones (white-tailed tropicbird, brown noddy, sooty tern, white tern). Although situated in a tropical region, the food availability in the Seychelles seems to be predictable at a large (annual) temporal scale, but highly unpredictable at a small (intra-seasonal or daily) temporal scale.

Trophic ecology of marine birds and pelagic fishes from Reunion Island as determined by stable isotope analysis

Stable nitrogen and carbon isotopes were used to investigate trophic ecology in tropical marine bird and fish communities from Reunion Island, western Indian Ocean. Firstly, isotope signa- tures in the liver of Barau's petrels Pterodroma baraui, Audubon's shearwaters Puffinus lherminieri bailloni, and white-tailed tropicbirds Phaethon lepturus were used to compare their trophic levels and determine whether they forage in the same areas while breeding on Reunion Island. Spatial and trophic segregations were noted among these seabirds. Barau's petrels seem to feed on prey of higher trophic levels than Audubon's shearwaters. Different isotopic signatures in adults and juveniles of these species suggest that these chick-rearing Procellariiformes adopt a dual food-provisioning strat- egy, making separate foraging trips to feed their fledglings and for their own maintenance. Satellite tracking should be undertaken to verify this hypothesis. Furthermore, novel data were obtained on the seabirds' interbreeding period by analyzing feather signatures. White-tailed tropicbirds are thought to change foraging areas during this season, although none of the birds seemed to shift diets. Secondly, isotopic signatures in the muscle of yellowfin tuna Thunnus albacares, skipjack tuna Katsuwonus pelamis, and common dolphinfish Coryphaena hippurus were used to gather informa- tion on their feeding behaviors in Reunion Island waters. Spatial and trophic segregations were also observed, particularly between common dolphinfish and the tuna species, where the former fed more on low trophic level coastal organisms under fish aggregating devices than did the latter. Finally, trophic interactions in bird and fish communities were investigated. Seabirds appear to be trophically more structured than fish, foraging in a wider range of areas. Our results confirmed feeding associa- tions between Audubon's shearwaters and yellowfin tuna.

Mercury in seabird feathers: Insight on dietary habits and evidence for exposure levels in the western Indian Ocean

Breast feathers were used to estimate mercury levels in six marine birds nesting in the tropical western Indian Ocean, i.e. Sooty Tern (Sterna fuscata), Brown Noddy (Anous stolidus), Lesser Noddy (Anous tenuirostris), Audubon Shearwater (Puffinus lherminieri bailloni), Barau's Petrel (Pterodroma baraui) and the White-tailed Tropicbird (Phaethon lepturus). Juveniles consistently showed lower plumage mercury than adults. The lowest mean level was noted in juvenile Sooty Terns from the Glorioso Archipelago (0.05 microg g(-1)). The highest levels were obtained for adult Barau's Petrels from Reunion Island (0.96 microg g(-1)). An inter-site analysis of Sooty Tern showed higher mercury levels in birds nesting on Juan de Nova Island. Levels were low in comparison with values reported in the plumage of seabirds worldwide. The potential impacts of the size, the type (fish/cephalopod) and the origin (epi-/meso-pelagic) of prey on mercury intake in birds are discussed. Although the diet composition of individuals within a species appeared to be quite variable, combining results on mercury levels with common knowledge of each species allowed additional information on their dietary and foraging habits to be unraveled.

Preliminary results on trace element levels in three species of seabirds from the western Indian Ocean

As top predators of pelagic food webs, marine birds naturally bioaccumulate essential and non-essential elements. Levels of arsenic (As), cadmium (Cd), copper (Cu), iron (Fe), mercury (Hg), manganese (Mn), selenium (Se) and zinc (Zn) were determined in the liver, kidneys and muscles of three species of marine birds found on Réunion Island: Barau's Petrel (Pterodroma baraui), Audubon's Shearwater (Puffinus lherminieri bailloni) and the White-tailed Tropicbird (Phaethon lepturus). The study of the 89 birds sampled put forth variations of the elemental levels between organs, age groups (juveniles versus adults) and species. Adult Barau's Petrels showed the highest values of Hg and Cd. This study offers a first glimpse of the levels of impregnation of eight trace elements in top predators of the western Indian Ocean and brings answers to certain questions related to the processes of bioaccumulation in marine top predators of the tropical Indian Ocean. Situés au sommet des réseaux trophiques pélagiques, les oiseaux marins bioaccumulent naturellement des éléments essentiels et non-essentiels tout au long de leur vie. La mesure des teneurs en arsenic (As), cadmium (Cd), cuivre (Cu), fer (Fe), mercure (Hg), manganèse (Mn), sélénium (Se) et zinc (Zn) a été effectuée dans le foie, les reins et les muscles de trois espèces d'oiseaux de l'île de La Réunion, le pétrel de Barau (Pterodroma baraui), le puffin de baillon (Puffinus lherminieri bailloni) et le paille-en-queue à brins blancs (Phaethon lepturus). L'étude des 89 oiseaux échantillonnés fait apparaître des variations des teneurs métalliques entre les organes, les classes d'âge (juvéniles vs adultes), ainsi qu'entre les espèces, les pétrels de Barau adultes ayant les plus fortes teneurs en Hg et Cd. Cette étude offre ainsi, un premier aperçu des niveaux d'imprégnation de 8 éléments traces chez des prédateurs supérieurs de l'Océan Indien occidental tropical et propose des éléments de réponses quant aux processus de bioaccumulation chez ces espèces.

Trace Elements in Three Marine Birds Breeding on Reunion Island (Western Indian Ocean): Part 1—Factors Influencing Their Bioaccumulation

This work aimed to use seabirds as bioindicators of trace element levels in the tropical waters and food webs of the Western Indian Ocean. The accumulation patterns of selected toxic (Cd and Hg) and essential (Cu, Fe, Mn, Se, and Zn) elements were determined in liver, kidney, and pectoral muscle of 162 marine birds belonging to 3 species collected in Reunion Island between 2002 and 2004. These pelagic seabirds belong to the following species: Barau's Petrel (Pterodroma baraui), Audubon's Shearwater (Puffinus lherminieri bailloni), and White-Tailed Tropicbird (Phaethon lepturus). Hg levels were also measured in breast feathers. Highest mean kidney Cd and liver Hg levels (respectively, 27.79 +/- 13.78 microg x g (-1) dry weight (dw) and 24.31 +/- 14.13 microg x g (-1) dw) were found in the squid-eating Barau's Petrel. Barau's Petrel feather Hg levels fell in the range of 0.6 to 2.7 microg x g(-1) dw previously reported for other petrels and shearwaters. The values of the other elements were also in the same range as those previously reported in the published literature concerning related seabirds, although Se and Zn burdens in the Reunion birds were among the highest values. Levels of Zn, Fe, and, to a lesser extent, Cu appeared to be regulated in seabird tissues. Uptake and pathways of metabolism and storage seemed to be similar for the five essential elements. The reproductive status of the bird did not seem to affect element levels, which, moreover, were not significantly different between male and female birds. However, trace elements in sampled birds varied according to the tissue considered, the age of the animal, and its species. Diet was seemingly a major influencing factor. Health status also appeared to have an impact on element levels.