Puffinus Gravis Research Articles

Low burrow occupancy and breeding success of burrowing petrels at Gough Island: a consequence of mouse predation

SummaryThe predatory behaviour of introduced house mice Mus musculus at Gough Island is known to impact on albatross and petrels, resulting in the Tristan Albatross Diomedea dabbenena and Atlantic Petrel Pterodroma incerta being listed as “Critically Endangered” and “Endangered”, respectively. Although predation has been documented for two burrowing petrels and one albatross species, the impact of house mice on other burrowing petrels on Gough Island is unknown. We report burrow occupancy and breeding success of Atlantic Petrels, Soft-plumaged Petrels Pterodroma mollis, Broad-billed Prions Pachyptila vittata, Grey Petrels Procellaria cinerea and Great Shearwaters Puffinus gravis. With the exception of the Great Shearwater, breeding parameters of burrowing petrels at Gough Island were very poor, with low burrow occupancy (range 4–42%) and low breeding success (0–44%) for four species, and high rates of chick mortality in Atlantic Petrel burrows. Breeding success decreased with mass, suggesting that smaller species are hardest hit, and winter-breeding species had lower breeding success than summer breeders. The results indicate that introduced house mice are having a detrimental impact on a wider range of species than previously recorded and are likely to be causing population declines among most burrowing petrels on Gough Island. The very low values of burrow occupancy recorded for Soft-plumaged Petrels and Broad-billed Prions and greatly reduced abundance of burrowing petrels in comparison to earlier decades indicate that Gough Island’s formerly abundant petrel populations are greatly threatened by the impact of predatory house mice which can only be halted by the eradication of this species from the island.

Diurnal seabird movements at Cabo Carvoeiro (Peniche, Portugal): observations in early October 2012

The ecology and movements of seabirds are still inadequately understood, mainly because they can rarely be studied efficiently from land. The potential of Cabo Carvoeiro (Peniche, Portugal) for monitoring seabird movements from land is poorly known internationally, as few results from this site have been published in English. Here we present data from standardised counts in October 2012 and draw attention to recent organised seabird counts in Portugal. Despite unfavourable weather conditions for concentrating seabirds towards land, we observed a strong passage of Northern Gannet Morus bassanus, Cory's Shearwater Calonectris diomedea, Great Skua Stercorarius skua, and Balearic Shearwater Puffinus mauretanicus (mean morning passage of 252, 99, 19, and 21 birds / hour, respectively). Manx Shearwater Puffinus puffinus, Sooty Shearwater P. griseus and Great Shearwater P. gravis occurred regularly in low numbers. Extrapolation indicates that thousands of seabirds passed daily within a few kilometres from land. The high counts of some species and the fairly high species diversity observed by us and in the RAM (Rede de observação de Aves e Mamiferos marinhos) initiative show that Cabo Carvoeiro is an outstanding site for monitoring and studying seabirds in the eastern Atlantic, as it is also located further south in the flyway than most other seawatch points. We hope this note will inspire ornithologists from other countries to participate in standardised seabird counts at Cabo Carvoeiro and other Portuguese sites.

ANISAKIASIS WITH PROVENTRICULAR PERFORATION IN A GREATER SHEARWATER (PUFFINUS GRAVIS) OFF THE COAST OF GEORGIA, UNITED STATES

A juvenile male greater shearwater (Puffinus gravis) found off the Georgia coast, United States, was lethargic, hypothermic, dehydrated, and emaciated. It was provided with supportive care but subsequently died. The coelomic cavity contained fibrinous fluid intermixed with hundreds of nematodes, some of which protruded through a perforation in the proventriculus. Nematodes were embedded in the wall of the proventriculus from the lamina propria to the serosal surface and were surrounded by granulocytes, epithelioid macrophages, multinucleate giant cells, lymphocytes, and fibroplasia. A full-thickness tear in the proventriculus was lined by heterophils and multinucleate giant cells. The nematode histomorphology was consistent with Anisakis spp. The definitive hosts of Anisakis spp. are marine mammals, which are infected through ingestion of parasitized fish and crustaceans. Marine birds are aberrant hosts of Anisakis spp., and young, inexperienced, immunocompromised birds might be more susceptible to severe infestations. Fatal anisakiasis is rarely reported in birds.

Predation of Atlantic Petrel chicks by house mice on Gough Island

The impacts of predation by invasive mammals on island fauna are a major driver of insular biodiversity loss. Devastating, hitherto unsuspected impacts of predatory house mice on breeding seabirds have been described recently. We studied the fate of 178 Atlantic Petrel Pterodroma incerta nests at Gough Island, over four seasons, from October 2003 to January 2008. Introduced house mice Mus musculus were found in all study burrows checked for mouse visits. From October 2003 to September 2004, we video-recorded attacks by mice on six (of 13) live, healthy Atlantic Petrel chicks and on one (of three) great shearwater Puffinus gravis chicks. In all years, chicks died from mouse attacks. Stage-specific daily nest survival rates were modelled, from which estimates of breeding success were derived that accounted for the variable exposure periods studied among years. Average daily survival rate of eggs was 0.998, and hatching success through the entire incubation period (55.5 days) was 0.924 [95% confidence interval (CI) 0.903–0.940]. Daily chick survival rates were 0.990, which gave a modelled fledging success of 0.247 (CI 0.165–0.338) over the 138-day chick period, and average annual breeding success (chicks fledged per breeding attempt) of 0.228 (CI 0.150–0.318), which is low compared with congeners. Productivity estimates were used as a parameter in a population simulation model, which predicted a population multiplication rate (λ) of 0.993 (CI = 0.966–1.021). However, in the one season studied from laying to fledging (2007), from 58 nests, only one chick fledged (1.7%). This suggests the wide errors on the model results may obscure a more severe reality. More than 60% of model simulations resulted in an International Union for Conservation of Nature classification of Endangered. Our results add support to calls to eradicate mice from Gough Island. More generally, mice cannot be ignored as a potential threat to island fauna, and island restoration and management plans should routinely include eradication of introduced mice.

Bycatch susceptibility in pelagic longline fisheries: are albatrosses affected by the diving behaviour of medium-sized petrels?

Species of petrels and shearwaters with high diving ability could facilitate the catch of albatrosses in pelagic longline fisheries, because they retrieve bait to the surface from depths that albatrosses cannot reach. Once on the surface, large seabirds such as albatrosses can easily displace smaller species thus gaining access to baited hooks which increases their likelihood of getting caught. This paper evaluates the extent to which diving species (i.e. Procellaria aequinoctialis, Procellaria conspicillata and Puffinus gravis) increase the susceptibility of albatross to bycatch in pelagic longline fisheries. In 48 sets, attacks on baits were quantified. When more than one bird (of the same or different species) tried to attack the same bait this was defined as a multiple attack. There were 384 attacks on baits, of which 260 were made by a single individual and 124 by more than one. Multiple attacks were the largest source of bycatch of albatrosses (22 of 27 albatrosses whose attacks were observed). Of the baits attacked by albatrosses (n = 244), 17% were indirectly facilitated by diving medium-sized petrels. Considering only the multiple attacks in which albatrosses participated (n = 114), 36% were initiated by these medium-sized petrels. Eleven (41%) of the albatrosses captured, and whose attacks were observed, resulted from a diving medium-sized seabird species first having contacted the terminal tackle. This paper shows that medium-sized petrels, with a strong ability to dive, increase considerably the access to bait, and indirectly, the incidental bycatch of albatrosses. Observations made in the absence of mitigation measures also provide useful information to improve the performance of tori lines. Based on the seabird behaviour, it is recommended that tori lines should have a minimum aerial coverage of 50 m. Copyright © 2012 John Wiley & Sons, Ltd.

ON THE RELATION OF ANTARCTIC AND SUBANTARCTIC SEABIRDS WITH ABIOTIC VARIABLES OF SOUTH AND SOUTHEAST BRAZIL

The distribution of wintering seabirds is influenced by biotic and abiotic oceanic processes. Ocean productivity is a main parameter at small and large scales, but the role of abiotic parameters at large scales may be explored indeed. Thus, we conduced bird counting between Rio grande and Rio de Janeiro (Brazil) onboard NApOc Ary Rongel from 11 until 13 april, 2009. The samples comprised 10 minutes each hour, from sunrise until sunset. Abiotic data were collected by NApOc Ary Rongel equipments. Data were analysed through CDA, PCA of species and CDA functions, and Multiple Regressions of CDA functions with sum of all Antarctic and Subantarctic abundances, and sum of all tropical and subtropical abundances. We verified Through PCA Thalassarche chlororhynchos and T. chrysostoma are associated with greater wind speed and air temperature, Calonectris diomedea and Puffinus gravis are associated with greater depths, sea temperature and atmospheric pressure. As a group, Antarctic / Subantarctic species are associated with higher wind speed, higher air temperature, lower atmospheric pressures and lower depths. Tropical / subtropical birds did not responded to any CDA functions. At small scales, seabirds tend to respond to gradients of productivity, chlorophyll concentrations, depth and salinity. Nonetheless at larger scales, Seabirds may be mainly driven by wind, associated with low pressures zones. At larger scales, the ability of disperse over greater distances may play a fundamental role.

Diving of Great Shearwaters (Puffinus gravis) in Cold and Warm Water Regions of the South Atlantic Ocean

BackgroundAmong the most widespread seabirds in the world, shearwaters of the genus Puffinus are also some of the deepest diving members of the Procellariiformes. Maximum diving depths are known for several Puffinus species, but dive depths or diving behaviour have never been recorded for great shearwaters (P. gravis), the largest member of this genus. This study reports the first high sampling rate (2 s) of depth and diving behaviour for Puffinus shearwaters.Methodology/Principal FindingsTime-depth recorders (TDRs) were deployed on two female great shearwaters nesting on Inaccessible Island in the South Atlantic Ocean, recording 10 consecutive days of diving activity. Remote sensing imagery and movement patterns of 8 males tracked by satellite telemetry over the same period were used to identify probable foraging areas used by TDR-equipped females. The deepest and longest dive was to 18.9 m and lasted 40 s, but most (>50%) dives were <2 m deep. Diving was most frequent near dawn and dusk, with <0.5% of dives occurring at night. The two individuals foraged in contrasting oceanographic conditions, one in cold (8 to 10°C) water of the Sub-Antarctic Front, likely 1000 km south of the breeding colony, and the other in warmer (10 to 16°C) water of the Sub-tropical Frontal Zone, at the same latitude as the colony, possibly on the Patagonian Shelf, 4000 km away. The cold water bird spent fewer days commuting, conducted four times as many dives as the warm water bird, dived deeper on average, and had a greater proportion of bottom time during dives.Conclusions/SignificanceGeneral patterns of diving activity were consistent with those of other shearwaters foraging in cold and warm water habitats. Great shearwaters are likely adapted to forage in a wide range of oceanographic conditions, foraging mostly with shallow dives but capable of deep diving.

Inter-annual variability in diet of non-breeding pelagic seabirds Puffinus spp. at migratory staging areas: evidence from stable isotopes and fatty acids

During nesting periods, seabirds are known to exhibit considerable inter-annual vari- ability in diets, yet little is known about the diets of pelagic seabirds during non-breeding periods. Over 5 yr (2005 to 2009), we studied dietary partitioning between sympatric greater and sooty shear- waters, Puffinus gravis and P. griseus, during migratory staging periods in the Northwest Atlantic. Stable-isotope (SI; n = 253) and fatty-acid (FA; n = 127) signatures from blood samples were used to assess inter-annual patterns in diet and quantify prey choices. In addition to significant effects of year, capture site, and body condition, SI signatures revealed subtle, but consistent, dietary partition- ing between species. In all years, greater shearwaters fed at slightly higher trophic levels (overall mean δ 15 N = 13.6‰) and lower δ 13 C (-19.1‰) than sooty shearwaters (δ 15 N = 13.3‰, δ 13 C = -18.9‰). SI mixing models revealed that sooty shearwaters relied more heavily on euphausiids Meganyc- tiphanes norvegica, while greater shearwaters consumed more herring Clupea harengus, squid Illex illecebrosus, and, in some years, mackerel Scomber scombrus. In 2005/2006, bird diets consisted pri- marily of herring and krill, but demonstrated a shift towards krill and squid during 2007-2009. FA from bird plasma showed little inter-specific partitioning but a strong signal of annual variation for both species. We used a subset of prey FA and a modified multivariate approach to model bird diets and obtained dietary preferences broadly in agreement with SI results. The present study revealed inter-annual variability and dietary partitioning in sympatric species of pelagic seabirds, and high- lights potential shifts in prey availability to predators in the Bay of Fundy.

The Tristan ThrushNesocichla eremitaas Seabird Predator

Tristan Thrushes or Starchies Nesocichla eremita are known to feed on seabird eggs. We show they are able to open the eggs of birds as large as small albatrosses. Starchies were involved in almost half of all egg losses by Great Shearwaters Puffinus gravis during the early incubation period in a small study colony at Inaccessible Island, South Atlantic Ocean. They also enter burrows to remove and kill petrel chicks up to at least 70 g. Starchies are thus potentially significant predators of seabird eggs and chicks, and may select against egg neglect and early cessation of brooding by burrowing petrels at the Tristan islands. Starchies previously were recorded killing adult White-bellied Storm Petrels Fregetta grallaria at Inaccessible Island. This behaviour now includes White-faced Storm Petrels Pelagodroma marina. It is likely that the Starchies hunt adult storm petrels directly, taking them from their burrows.

Feeding habits of the blue shark (Prionace glauca) off the coast of Brazil

Stomachs from 222 blue sharks collected along the Brazilian coast were analyzed - 116 from the northeastern region and 106 from the southern region. A total of 51 prey taxa were identified. The most important prey items in the southern region were Mysticeti whales, teleosteans, the gempylid Ruvettus pretiosus and the nomeid Arioma bondi. Cephalopods were more diverse, with dominance of vertical migrants Histioteuthis spp., Cranchiidae and the epipelagic octopus Ocythoe tuberculata. In the northeastern region, blue sharks consumed mainly teleosteans, including the alepisaurid Alepisaurus ferox and the gempylid Gempylus serpens. Among cephalopods, Histioteuthis spp. and the epipelagic octopus Tremoctopus violaceus were the dominant items. Predation upon schooling prey was occasional, as observed on Arioma bondi. Birds also were consumed in both regions; Puffinus gravis was the fifth most frequent item in the northeastern region. During the reproductive migration cycle, blue sharks likely prey in the thermocline, which is deeper in the northeastern region and closer to the surface in the southern region.

Occurrence of plastic particles in procellariiforms, south of São Paulo state (Brazil)

Seabirds ingest plastic particles floating on the surface of the world's oceans. The birds can ingest plastic particles that they mistakenly identify as prey items. Alternatively, plastics can be taken up in the stomach contents of prey species. Plastic is often passed from parents to chicks in regurgitated food. In this study, individual petrels and albatrosses brought in by the tide onto Ilha Comprida beach between January 2000 and December 2002 were collected. Ilha Comprida, a barrier island in southern São Paulo, Brazil, was traversed by car along a transect of 70 kilometers. A total of 110 birds of 10 species were collected and 64.54% had plastic particles in their stomach. Frequencies of occurrence were Macronectes giganteus (64.28%), Thalassarche melanophrys (73.07%), Thalassarche chlororhinchos (44.44%), Puffinus puffinus (85.71%), Puffinus gravis (7.41%), Puffinus griseus (63.63%), Fumarus glacialoides (33.33%), Daption capensis (75%), Pachyptila belcheri (33.33%), Procellaria aequinoctialis (25%). These results demonstrated the extent of contamination with plastic and the possible harmful effects on seabirds.

Plastic ingestion by Procellariiformes in Southern Brazil

The Procellariiformes are the birds most affected by plastic pollution. Plastic fragments and pellets were the most frequent items found in the digestive tract of eight species of Procellariiformes incidentally caught by longline fisheries as well as beached birds in Southern Brazil. Plastic objects were found in 62% of the petrels and 12% of the albatrosses. The Great shearwater, Manx shearwater, Cory’s shearwater and Antarctic fulmar were found to have greater quantities and frequencies of occurrence of plastic. There was no significant difference in the number of plastics between the birds from longline fisheries and beached birds. No correlation was found between the number of prey and number of plastics in the digestive tract of the birds analyzed, but this does not discard the hypothesis that, in some cases, the presence of plastic in the digestive tract has a negative effect on the feeding efficiency of these birds.

Synthetic polymers in the marine environment: A rapidly increasing, long-term threat

Synthetic polymers, commonly known as plastics, have been entering the marine environment in quantities paralleling their level of production over the last half century. However, in the last two decades of the 20th Century, the deposition rate accelerated past the rate of production, and plastics are now one of the most common and persistent pollutants in ocean waters and beaches worldwide. Thirty years ago the prevailing attitude of the plastic industry was that “plastic litter is a very small proportion of all litter and causes no harm to the environment except as an eyesore” [Derraik, J.G.B., 2002. The pollution of the marine environment by plastic debris: a review. Mar. Pollut. Bull. 44(9), 842–852]. Between 1960 and 2000, the world production of plastic resins increased 25-fold, while recovery of the material remained below 5%. Between 1970 and 2003, plastics became the fastest growing segment of the US municipal waste stream, increasing nine-fold, and marine litter is now 60–80% plastic, reaching 90–95% in some areas. While undoubtedly still an eyesore, plastic debris today is having significant harmful effects on marine biota. Albatross, fulmars, shearwaters and petrels mistake floating plastics for food, and many individuals of these species are affected; in fact, 44% of all seabird species are known to ingest plastic. Sea turtles ingest plastic bags, fishing line and other plastics, as do 26 species of cetaceans. In all, 267 species of marine organisms worldwide are known to have been affected by plastic debris, a number that will increase as smaller organisms are assessed. The number of fish, birds, and mammals that succumb each year to derelict fishing nets and lines in which they become entangled cannot be reliably known; but estimates are in the millions. We divide marine plastic debris into two categories: macro, >5 mm and micro, <5 mm. While macro-debris may sometimes be traced to its origin by object identification or markings, micro-debris, consisting of particles of two main varieties, (1) fragments broken from larger objects, and (2) resin pellets and powders, the basic thermoplastic industry feedstocks, are difficult to trace. Ingestion of plastic micro-debris by filter feeders at the base of the food web is known to occur, but has not been quantified. Ingestion of degraded plastic pellets and fragments raises toxicity concerns, since plastics are known to adsorb hydrophobic pollutants. The potential bioavailability of compounds added to plastics at the time of manufacture, as well as those adsorbed from the environment are complex issues that merit more widespread investigation. The physiological effects of any bioavailable compounds desorbed from plastics by marine biota are being directly investigated, since it was found 20 years ago that the mass of ingested plastic in Great Shearwaters was positively correlated with PCBs in their fat and eggs. Colonization of plastic marine debris by sessile organisms provides a vector for transport of alien species in the ocean environment and may threaten marine biodiversity. There is also potential danger to marine ecosystems from the accumulation of plastic debris on the sea floor. The accumulation of such debris can inhibit gas exchange between the overlying waters and the pore waters of the sediments, and disrupt or smother inhabitants of the benthos. The extent of this problem and its effects have recently begun to be investigated. A little more than half of all thermoplastics will sink in seawater.

An effective method for trapping scavenging seabirds at sea

ABSTRACT Most studies of seabirds that involve trapping and marking birds are carried out at breeding colonies. This bias toward the breeding period and colony-based research is partially caused by difficulties in capturing birds at sea. From 2005 to 2007, we used a cast net thrown by hand from a fishing boat to capture albatrosses and petrels at sea in the southwestern Atlantic Ocean. About 500 birds of 13 species were captured, ranging in size from the 30-g Wilson's Storm-petrel (Oceanites oceanicus) to the 10-kg Wandering Albatross (Diomedea exulans). Cast nets are potentially useful for capturing any seabird that can be attracted close to fishing vessels by bait, such as sardines, squid, offal, or shark liver, thrown into the water. Our method was most effective for capturing bold species, such as Cape (Daption capense), Spectacled (Procellaria conspicillata), and White-chinned (Procellaria aequinoctialis) petrels and Great Shearwaters (Puffinus gravis), but was not effective for capturing shy species, such as Cory's (Calonectris diomedea), Cape Verde (Calonectris edwardsii) and Manx (Puffinus puffinus) shearwaters, species that rarely sit on the water, such as Wilson's Storm-petrels, Thin-billed (Pachyptila belcheri) and Antarctic (Pachyptila desolata) prions and Atlantic Petrels (Pterodroma incerta), and species with excellent diving abilities, such as Sooty Shearwaters (Puffinus griseus). For many species of seabirds, cast nets would likely be more efficient for capturing large numbers of birds than other methods, such as hoop nets. La mayoría de los estudios sobre aves marinas son realizados en sus colonias de anidación. La dificultad para capturar aves en el mar en parte ha limitado el conocimiento sobre estas aves durante el periodo invernal. Entre 2005 y 2007 se empleó una red tipo atarraya para capturar albatros y petreles en el Océano Atlántico Sur Occidental. Fueran capturadas cerca de 500 aves de 13 especies y diferentes tamaños, desde el Petrel de las Tormentas de Wilson (Oceanites oceanicus) con solo 30 g de peso, hasta el Albatros Errante (Diomedea exulans) de 10 Kg. El método de captura es potencialmente aplicable a cualquier ave marina que se acerque a las embarcaciones pesqueras atraída por carnadas o descartes como sardinas, calamares, o hígado de tiburones. Este método fue más eficiente para la captura de especies confiadas, por ejemplo los Petreles Damero (Daption capense), de Antifaz (Procellaria conspicillata), Negro (Procellaria aequinoctialis) y la Pardela Capucho Negro (Puffinus gravis), pero no fue eficiente para la captura de especies tímidas cómo las Pardelas Cenicienta (Calonectris diomedea), de Cabo Verde (Calonectris edwardsii) y Común (Puffinus puffinus), para especies que difícilmente posan sobre el agua cómo el Petrel de las Tormentas de Wilson, Petreles Ballena de Pico Delgado (Pachyptila belcheri) y Ancho (Pachyptila desolata) y el Petrel Alas Negras (Pterodroma incerta), o especies con muy buena capacidad de buceo cómo la Pardela Negra (Puffinus griseus). Para muchas especies de aves marinas la red de atarraya es probablemente más eficiente para la captura en el mar que otros métodos que se han empleado como las redes de aro.

Seabirds indicate changes in the composition of plastic litter in the Atlantic and south-western Indian Oceans

I compare plastic ingested by five species of seabirds sampled in the 1980s and again in 1999–2006. The numbers of ingested plastic particles have not changed significantly, but the proportion of virgin pellets has decreased 44–79% in all five species: great shearwater Puffinus gravis, white-chinned petrel Procellaria aequinoctialis, broad-billed prion Pachyptila vittata, white-faced storm petrel Pelagodroma marina and white-bellied storm petrel Fregetta grallaria. The populations sampled range widely in the South Atlantic and western Indian Oceans. The most marked reduction occurred in great shearwaters, where the average number of pellets per bird decreased from 10.5 to 1.6. This species migrates between the South and North Atlantic each year. Similar decreases in virgin pellets have been recorded in short-tailed shearwaters Puffinus tenuirostris in the Pacific Ocean and northern fulmars Fulmarus glacialis in the North Sea. More data are needed on the relationship between plastic loads in seabirds and the density of plastic at sea in their foraging areas, but the consistent decrease in pellets in birds suggests there has been a global change in the composition of small plastic debris at sea over the last two decades.

Shearwater diet during migration along the coast of Rio Grande do Sul, Brazil

The coastline of the state of Rio Grande do Sul (Brazil) is used annually as a migratory route by a number of seabird species. Thirteen surveys were carried out between July 1997 and July 1998 to obtain information on the diet of Puffinus gravis, Puffinus griseus, and Puffinus puffinus along the coast of Rio Grande do Sul. Sampling efforts focused on dead beach-cast specimens. One hundred twenty-one stomach content analyses were performed on P. gravis from a total of 238 specimens; 17 stomach content analyses were performed on P. griseus from a total of 54 specimens; and 25 stomach content analyses were performed on 25 P. puffinus from a total of 61 dead specimens. Cephalopods were the main prey found in the stomachs of the three species and were present in 96% of the P. gravis stomachs. The following cephalopods were observed: Ommastrephidae, Gonatus antarcticus, Gonatus sp., Lycoteuthis lorigera, Lycoteuthis sp., Histioteuthis sp., Cycloteuthis sp., Loligo plei, Loligo sanpaulensis, Sepiidae, and Argonauta nodosa. The latter was the most abundant species in the three species of Puffinus. The following fish were identified from otoliths: Porichthys porosissimus, Ctenosciaena gracilicirrhus, Paralonchurus brasiliensis, Cynoscion guatucupa, and Trichiurus lepturus. There was also a high incidence of synthetic materials such as plastic, polyethylene and rubber.

Breeding biology, chick growth and provisioning of Great Shearwaters (Puffinus gravis) at Gough Island, South Atlantic Ocean

The Great Shearwater (Puffinus gravis) is the largest (860 g) and most abundant shearwater species of the South Atlantic Ocean, with a breeding population of six million pairs on the islands of Gough and Tristan da Cunha. The breeding ecology of the species was studied on Gough Island from September 2000 to May 2001. The breeding cycle of Great Shearwaters was ∼7.5 months from time of arrival to departure, with a highly synchronised return of birds to their burrows in mid-September, departure for a pre-laying exodus of ∼1 month from mid-October, and a peak of laying around 21 November. Chicks fledged by mid-May after an average rearing period of 108 days. Overall breeding success was 66%, with hatching (56%) and fledging (93%) success within the normal range for Puffinus species. Chick growth followed the normal pattern for Procellariiformes, gaining body mass rapidly to a maximum mass of ∼150% of adult mass, and then losing weight until fledging. Chicks were fed large meals (188 g) but only infrequently (every 3–4 days), with 22% of all meals delivered during daylight hours. The long interval between feeds suggests that adult Great Shearwaters could be foraging at a great distance from the breeding colonies.

The summer seabird community of the Flemish Cap in 2002

We describe the seabird community and the distribution of seabirds in the Flemish Cap in the summer of 2002. Data were collected by means of sixty-six 300 m wide boat transects of varied length in the first half of July. A total of 802 seabirds and 8 species were counted within census transects. Over 70% of seabirds were Great Shearwaters (Puffinus gravis), followed by Northern Fulmars (Fulmarus glacialis) with 17.1% of the seabirds recorded. The number of seabirds recorded per census transect was, on average, very low (mean = 10.68, SD = 19.54) and no seabirds were observed in 20 transects. Overall seabird abundance was 8.78 birds km-1 (n = 66, SD = 16.98). Seabird abundance and seabird species richness were not evenly distributed across the Flemish Cap but seemed to concentrate at the edges of the southern half of the study area. This pattern suggests that seabirds were mostly distributed in the area of confluence of the North Atlantic Current with the Labrador Current. We also call attention on the possibility that the Flemish Cap may be an important area for wintering Great Shearwaters.

Breeding biology of the Atlantic Petrel, Pterodroma incerta, and a population estimate of this and other burrowing petrels on Gough Island, South Atlantic Ocean

The Atlantic Petrel, Pterodroma incerta, endemic to the Tristan da Cunha group in the South Atlantic and globally threatened, is one of the least known of the world's seabirds. At Gough Island, Atlantic Petrels are winter breeders, with single eggs laid in June—July and chicks fledging in December. Birds were exclusively nocturnal on land. The pre-egg exodus of ∼50 days and nestling period of almost 140 days are near the longest recorded for Pterodroma species, and support the general pattern of prolonged development found in winter-breeding Procellariiformes. Chicks grew at a very slow rate, suggesting poor at-sea feeding conditions. Breeding success averaged only 20% and introduced House Mice, Mus musculus, were probably responsible for considerable losses of chicks in two breeding seasons. Preliminary population modelling predicts a decline in numbers. The potential impact of introduced mice suggests that the species’ conservation status be upgraded from Vulnerable to Endangered and that further research on this issue is a high priority. The first quantitative estimate of breeding numbers indicates a population of ∼1.8 million pairs of Atlantic Petrels. Provisional population estimates of Great Shearwaters, Puffinus gravis (980000 pairs), Soft-plumaged Petrels, Pterodroma mollis (400000 pairs), and Broad-billed Prions, Pachyptila vittata (1750000 pairs) confirm the international significance of Gough Island as a site for breeding seabirds.

Attendance of scavenging seabirds at trawler discards off Galicia, Spain

The occurrence of scavenger seabirds at fishing trawlers was studied off Galicia, Spain. A total of 9,368 seabirds of 23 species were recorded during 92 fishing operations in 1998 and 1999. The most common species were the yellow-legged and lesser black-backed gull ( Larus cachinnans and L. fuscus ), Sabine´s gull ( L. sabini ), the northern gannet ( Morus bassanus ), the great shearwater ( Puffinus gravis ), sooty shearwater (P. griseus), the Manx and Balearic shearwater ( P. puffinus and P. mauretanicus ), the great skua ( Catharacta skua ) and terns (mainly Sterna hirundo and S. paradisaea ). Other species occurred in small numbers: Leach´s petrel ( Oceanodroma leucorhoa ), the storm petrel ( Hydrobates pelagicus ), the little shearwater ( Puffinus assimilis ), Cory´s shearwater ( Calonectris diomedea ), the parasitic skua ( Stercorarius parasiticus ), the pomarine skua ( S. pomarinus ), the black-headed gull ( Larus ridibundus ), the glaucous gull ( L. hyperboreus ), the kittiwake ( Rissa tridactyla ), the sandwich tern (Sterna sandvicensis), the black tern (Chlidonias niger), the guillemot ( Uria aalge ) and the little auk ( Alle alle ). The maximum number of seabirds recorded at a haul was 320. The maximum number of a particular species ranged from 120 great shearwaters to 250 yellow-legged/lesser black-backed gulls during a single haul. The differences in ship-follower species abundance are related to migratory movements but fisheries could also have a strong influence at a smaller scale on the distribution of seabirds off Galicia. The degree to which seabirds rely on fishery discards as food was not quantified, but may be important for several species.