Puffinus Griseus Research Articles

Integrating habitat and partial survey data to estimate the regional population of a globally declining seabird species, the sooty shearwater

Many animal populations are thought to be in flux due to anthropogenic impacts. However, censusing organisms to understand such changes is often impractical. For example, while it is thought that over half of pelagic seabird populations are declining, most breed in burrows or on cliffs, in large, remote colonies, making them difficult to count. Burrow-nesting sooty shearwaters (Ardenna grisea) are abundant but declining in their core (South Pacific) breeding range, potentially due to introduced rodents and habitat loss. In contrast, Kidney Island, their largest colony in the Falkland Islands (Southwest Atlantic), purportedly grew by several orders of magnitude since the mid-1900s. This island is rodent-free, and native tussac grass (Poa flabellata) has increased following cessation of historical exploitation. To estimate the sooty shearwater population in the Falkland Islands, and its relationship with breeding habitat availability, we sampled burrow density and occupancy on Kidney Island and modeled these as functions of habitat. Both indices responded positively to a proxy for historical increases in tussac cover. We estimate that breeding sooty shearwaters occupy ∼140,000 (95% CI: 90,000–210,000) burrows on Kidney Island. Moreover, using additional survey data and Generalized Functional Response models to account for intra-island variation in habitat availability, we estimate that 25,000 (95% CI: 20,100 - 30,500) burrows could be occupied on nearby islands from which non-native rodents have been recently eradicated. Our study shows that habitat selection functions, generalized where necessary, not only improve population estimates but provide biological insights needed to reverse declines in seabirds and other species.

The depth of Sooty Shearwater Ardenna grisea burrows varies with habitat and increases with competition for space

The Sooty Shearwater Ardenna grisea, an abundant but declining petrel, is one of many seabird species that construct breeding burrows, presumably because these confer protection from predators and the elements. Little is known about the causes of variation in Sooty Shearwater burrow architecture, which can differ markedly both within and between breeding sites. We hypothesize that burrow architecture varies in response to habitat type and competition for space. To address these hypotheses, we recorded Sooty Shearwater burrow dimensions on Kidney Island, the largest Sooty Shearwater colony in the Falkland Islands, South Atlantic, and modelled these as functions of burrow density (a proxy for competition) and habitat indices. Our models suggest that Sooty Shearwaters burrow further underground in response to competition for breeding space, and that soil underlying dense tussac grass Poa flabellata is more easily excavated than other substrates, indicating how vegetation restoration could aid the conservation of this species.

First records from the Mediterranean of a Sooty Shearwater Ardenna grisea caught accidentally by a surface longline

First records from the Mediterranean of a Sooty Shearwater Ardenna grisea caught accidentally by a surface longline

Dietary Niche Shifts of Multiple Marine Predators under Varying Prey Availability on the Northeast Newfoundland Coast

Understanding species interactions among top marine predators and interactions with their prey can provide important insight into community-level responses to changing prey availability and the role of apex predators as indicators of ecosystem change. On the northeast Newfoundland coast, marine predators rely on capelin (Mallotus villosus), a dominant forage fish, as a food source. Capelin migrate into coastal regions to spawn during July, essentially transforming food supply from low during early summer (i.e. pre-spawning) to high later in the summer (i.e. spawning). During July-August, 2016, we used stable isotopic ratios of nitrogen (δ15N) and carbon (δ13C) to investigate shifts in dietary niche metrics at the predator group-level (trophic position, dietary niche breadth) and community-level (niche overlap, trophic diversity) for multiple marine predators under varying capelin availability. Predator groups included non-breeding shearwaters (great shearwater Ardenna gravis, sooty shearwater A. grisea), humpback whales (Megaptera novaeangliae), and gull chicks (herring gull Larus argentatus, great black-backed gull L. marinus). We also tested the sensitivity of community-level dietary metrics to a variety of published trophic discrimination factors. Tissue samples from shearwaters (blood cellular component), gull chicks (whole blood), and whales (skin), representing average diets over 2-3 weeks, were collected during three periods (early, mid, late) corresponding to increasing capelin availability. Isotopic niche breadth (Standard Ellipse Area, SEAb) narrowed and trophic position shifted toward higher δ15N for all predator groups as capelin availability increased, suggesting a higher reliance on capelin. Trophic diversity (distance to centroid) decreased with increased capelin availability, while pairwise niche overlap between predator groups was highly variable and sensitive to varying trophic discrimination factors. Findings suggest that although capelin is the dominant forage fish during the summer, predators rely on capelin as prey to varying degrees. Combining species- and community-level metrics of dietary niche and trophic diversity may provide a more complete picture of predator responses to prey availability and, thus, may be important monitoring tools to indicate changes in the food supply of marine predators.

Predator–prey interactions influenced by a dynamic river plume

Marine predator–prey interactions are often influenced by oceanographic processes that aggregate prey. We examined density distributions of seabirds and prey fish associated with the Columbia River plume to determine whether variation in plume size (i.e., volume or surface area) or location influences predator–prey interactions. Common murre (Uria aalge), sooty shearwater (Ardenna grisea), and forage fish, including northern anchovy (Engraulis mordax) and juvenile salmon (Oncorhynchus spp.), occurred disproportionately in plume waters relative to adjacent marine waters. Water clarity, an indicator of plume-influenced waters, was a significant predictor of seabird and prey densities throughout the survey area. Murres occurred within 20 km of the plume center of gravity, whereas shearwaters occurred ∼100 km north of the plume center of gravity, concurrent with the highest densities of prey fish. Global indices of collocation were relatively low between murres and prey compared with the high values between shearwaters and prey. Seabird densities were negatively correlated with plume size, suggesting that seabirds concentrate in the plume to maximize foraging effort. We conclude that variation in Columbia River plume size and location influences predator distributions, which increases predation pressure on prey, including threatened salmonid species.

Offshore surprises: new at-sea bird records for Suriname (2013\u20132015)

Bird observations were collected from various types of survey vessels in Suriname’s territorial waters between 2013 and 2015. Dedicated, effort-related surveys were carried out from geophysical seismic survey vessels within an area located 80–110 km offshore (in 2013) and 165–290 km (in 2015). Opportunistic observations were recorded during fisheries surveys on a shrimp trawler operating along the 30 m depth contour, approximately 40–60 km offshore (in 2014). In total, 10 bird (sub-)species were observed during these surveys that previously were not recorded for Suriname, including Manx Shearwater Puffinus puffinus, Ruff Calidris pugnax, South Polar Skua Stercorarius maccormicki, Long-tailed Jaeger Stercorarius longicaudus, Sandwich Tern Thalasseus sandvicensis (ssp. acuflavidus), Roseate Tern Sterna dougallii, Bridled Tern Onychoprion anaethetus, Black Noddy Anous minutus, Scarlet Tanager Piranga olivacea and Black-and-white Warbler Mniotilta varia. In addition, Lesser Black-backed Gull Larus fuscus and Bulwer’s Petrel Bulweria bulwerii were photographed for the first time in Suriname. A Sooty Shearwater Ardenna grisea was recorded just outside the Exclusive Economic Zone (EEZ), and therefore does not count as a new country record. This paper contributes to a better understanding of the avifauna frequenting the waters off Suriname, which historically has been poorly studied. Most of the species reported here are migratory. The timing of our sightings therefore also helps in a better understanding of their at-sea distribution and migration patterns.

Noteworthy seabird records from Paraná state, southern Brazil

We inventoried seabird specimens—skeletons and skins—collected during beach surveys of Parana, south Brazil, both the mainland coast and offshore islets during the period 1992–94. We found 184 specimens comprising four orders and 17 species. This represents the most important collection of seabirds from Parana and includes three new records for the state, Cory's Shearwater Calonectris borealis, Sooty Shearwater Puffinus griseus and Snowy Sheathbill Chionis albus. We recommend the removal of two species from the avifauna of Parana—Shy Albatross Thalassarche cauta and Broad-billed Prion Pachyptila vittata—due to the lack of tangible evidence. All of this material is held in publicly accessible natural history museums.

Westward range extension of Short-tailed Shearwaters Ardenna tenuirostris in the Southern Ocean

Short-tailed Shearwaters Ardenna tenuirostris are transequatorial migrants that breed at islands in southern Australia and spend the austral winter in the North Pacific. Adults feeding chicks undertake long foraging trips into Antarctic waters (to 70 degrees S) across a broad longitudinal range (mainly 55-180 degrees E). In mid-March 2017, we observed thousands of shearwaters in the vicinity of Bouvetoya (from 55 degrees S 0 degrees E to 50 degrees S 8 degrees E). These observations occurred more than 2000 km west of the documented range of this species, and raise the possibility that some Shorttailed Shearwaters migrate to the North Atlantic Ocean. Further observations are needed to determine whether this is a regular behaviour that has been overlooked in the past due to confusion with Sooty Shearwaters A. grisea, or whether 2017 was an unusual year for Short- tailed Shearwaters.

Fortune telling seabirds: sooty shearwaters (Puffinus griseus) predict shifts in Pacific climate

Indices calculated from “muttonbirding” diaries collected by the Rakiura Māori of New Zealand were correlated with future values of the Southern Oscillation Index (SOI), and the Pacific Decadal Oscillation (PDO) from 1957 to 2010. Spearman correlations showed that La Nina events tended to occur after those harvest seasons with relatively high success and chick size, whereas El Nino events tended to occur after harvest seasons with relatively low success and chick size. Generalized boosted regression models show that chick size alone is able to predict shifts in SOI from 0 to 12 months after the harvest. A model that included chick size, 2-year average PDO (prior to the harvest), and one year averages of SOI (prior to the harvest), was able to predict shifts in SOI 13–20 months after the harvest. It is likely that sooty shearwater adults (and therefore chick size and quantity) are being affected by oceanographic conditions that are also precursors to shifts in SOI, and that there is a complex interaction between PDO prior to the harvest, the harvest indices and SOI. The location and timing of adult birds at the time they are provisioning chicks could lead to potential mechanisms and requires further study.

Human exploitation assisting a threatened species? The case of muttonbirders and Buller's albatross.

Albatrosses are flexible and adaptable predators, relying on live prey as well as carrion. Use of predictable food sources and reliance on human-produced resources are well-known trait in long-range feeders like albatrosses and petrels. Breeding Buller’s albatrosses studied at Solander I. (Hautere), New Zealand fed their chicks the remains of sooty shearwater juveniles (tītī in Māori), which are harvested from nearby muttonbirding sites. Evidence of this food type was found at over 10% of nests examined, and 17–40% birds that were fitted with GPS loggers visited muttonbirding sites in this and previous studies. Muttonbirding is a traditional practice that has continued for centuries, with up to 120 tonnes of offal discharged to the sea annually during the present day harvest. It coincides with the energetically-demanding early chick period for the albatrosses. Our finding suggests that the offal may be an important, but overlooked element in the albatross diet. As an important supplementary food for the albatrosses it is likely to have contributed to the 3% per annum growth of their populations since the first comprehensive population surveys in 1969.

Modeling Nonresident Seabird Foraging Distributions to Inform Ocean Zoning in Central California.

Seabird aggregations at sea have been shown to be associated with concentrations of prey. Previous research identified Central California as a highly used foraging area for seabirds, with locally breeding seabirds foraging close to their colonies on Southeast Farallon Island. Herein, we focus on nonresident (i.e. non-locally breeding) seabird species off of Central California. We hypothesized that high-use foraging areas for nonresident seabirds would be influenced by oceanographic and bathymetric factors and that spatial and temporal distributions would be similar within planktivorous and generalist foraging guilds but would differ between them. With data collected by the Applied California Current Ecosystem Studies (ACCESS) partnership during cruises between April and October from 2004–2013, we developed generalized linear models to identify high-use foraging areas for each of six nonresident seabird species. The four generalist species are Phoebastria nigripes (black-footed albatross), Ardenna griseus (sooty shearwater), Ardenna creatopus (pink-footed shearwater), and Fulmarus glacialis (northern fulmar). The two planktivorous species are Phalaropus lobatus (red-necked phalarope) and Phalaropus fulicarius (red phalarope). Sea surface temperature was significant for generalist species and sea surface salinity was important for planktivorous species. The distance to the 200-m isobath was significant in five of six models, Pacific Decadal Oscillation with a 3-month lag in four models, and sea surface fluorescence, the distance to Cordell Bank, and depth in three models. We did not find statistically significant differences between distributions of individual seabird species within a foraging guild or between guilds, with the exception of the sooty shearwater. Model results for a multi-use seabird foraging area highlighted the continental shelf break, particularly within the vicinity of Cordell Bank, as the highest use areas as did Marxan prioritization. Our research methods can be implemented elsewhere to identify critical habitat that needs protection as human development pressures continue to expand to the ocean.

Size and dynamics of microplastic in gastrointestinal tracts of Northern Fulmars (Fulmarus glacialis) and Sooty Shearwaters (Ardenna grisea)

We found microplastic in 89.5% of 143 Northern Fulmars from 2008 to 2013 and 64% of 25 Sooty Shearwaters in 2011–2012 that were found dead or stranded on Oregon and Washington beaches. Average plastic loads were 19.5 pieces and 0.461g for fulmars and 13.3 pieces and 0.335g for shearwaters. Pre-manufactured plastic pellets accounted for 8.5% of fulmar and 33% of shearwater plastic pieces. In both species, plastic in proventriculi averaged 2–3mm larger in greatest dimension than in ventriculi. Intestinal plastic in fulmars averaged 1mm less in greatest dimension than ventricular plastic. There was no significant reduction in pieces or mass of plastic in 33 fulmars held for a median of seven days in a plastic-free environment. Three fulmars that survived to be released from rehabilitation regurgitated plastic, which provided an alternative outlet for elimination of plastic and requires reassessment of the dynamics of plastic in seabird gastrointestinal tracts.

Evidence of an unreported negative effect of fisheries discards on seabirds: death by choking on the Atlantic Midshipman, Porichthys porosissimus, in southern Brazil

The effects of the fishing industry on the marine environment have been studied and described over the past two decades. Trawl-netting is a common but non-selective method of fishing that often captures non-target specimens of no commercial value that are discarded at sea. We discovered an unreported threat caused by fisheries discards on seabirds attending fishing activities in Brazilian waters: choking by feeding on discarded Atlantic Midshipman (Porichthys porosissimus). Over 6 years of monitoring (2007–13), we recorded five procellariiform species—Atlantic Yellow-nosed Albatross (Thalassarche chlororhynchos), Cory's Shearwater (Calonectris diomedea), Sooty Shearwater (Ardenna grisea), Great Shearwater (Ardenna gravis) and Manx Shearwater (Puffinus puffinus)—dead on beaches with Atlantic Midshipman stuck in their throats and showing evidence of death by suffocation as a result of blockage of the airways through choking. This phenomenon has not been consistently described, and the consequences of the consumption of fishery discards by seabirds in Brazilian waters remain poorly understood.

Persistence of hotspots and variability of seabird species richness and abundance in the southern California Current

Aggregations of seabirds at sea may provide information on centers of enhanced trophic interactions and concentrating mechanisms, however, to date most studies lack quantification of persistence, a key hotspot characteristic. Persistence statistics may reduce uncertainty about seabird habitat use, improve understanding of the spatio‐temporal scales of pelagic food web dynamics, and inform conservation planning. Using 26 years (1987–2012, 47 surveys) of shipboard surveys from a 300K km2 study area within the southern California Current Ecosystem, we conduct a spatial assessment of the inter‐annual and seasonal dynamics of the persistence of seabird hotspots and identify recurring sites of elevated seabird species richness and abundance. Previous studies document declines in abundance, but were based on broad spatial standardizations to assess where declines may have occurred. Here, we refine the hypothesis that seabird populations have declined off southern California by focusing on persistently used habitats in nearshore or offshore domains. We demonstrate that spatio‐temporal variability of seabird distribution and abundance is characterized by anomalous events embedded within trends. In addition to identifying the locations of persistence of seabird aggregations, we found significant declines in species richness and the density of sooty shearwater (Puffinus griseus) and Leach's storm petrel (Oceanodroma leucorhoa); in contrast, black‐footed albatross (Phoebastria nigripes) abundance appear to be increasing. This assessment provides a spatially‐explicit framework for future evaluations of biophysical drivers of seabird hotspots and their associations and impacts on forage fish and zooplankton populations.

Nutritional composition of Mutton bird (Puffinus griseus) meat

Mutton birds (Puffinus griseus) are wild seabird chicks traditionally harvested by Maori but available commercially for seasonal consumption in New Zealand. Little information is available on the nutritional content of the meat from these birds. Proximate analysis and amino and fatty acid composition of Mutton bird breast meat (MBBM) were measured over two harvesting seasons, 2007 and 2008. Protein content was lower, and fat and ash contents were higher (P<0.05) in meat from birds harvested in 2008 (18.5, 13.0 and 11.7%, respectively) compared with that from 2007 (20.3, 11.8 and 10.3%, respectively). Higher lysine concentrations and lower proline, cysteine and methionine were found in MBBM compared with literature values for beef, lamb and pork. The essential amino acid content in Mutton bird (41.7 and 38.4% for 2008 and 2007, respectively) was slightly lower than those reported for common meats (42–43%). Palmitic, arachidonic, DHA, stearic, EPA, and oleic were the major fatty acids (FA) detected in MBBM and accounted for approximately 60% of the FA. The cholesterol concentration was not affected by season. Seasonal variations MBBM existed which may be of little nutritional consequence but might be a useful indicator for ecological events including changing feed availability.

Estimating Regions of Oceanographic Importance for Seabirds Using A-Spatial Data.

Advances in GPS tracking technologies have allowed for rapid assessment of important oceanographic regions for seabirds. This allows us to understand seabird distributions, and the characteristics which determine the success of populations. In many cases, quality GPS tracking data may not be available; however, long term population monitoring data may exist. In this study, a method to infer important oceanographic regions for seabirds will be presented using breeding sooty shearwaters as a case study. This method combines a popular machine learning algorithm (generalized boosted regression modeling), geographic information systems, long-term ecological data and open access oceanographic datasets. Time series of chick size and harvest index data derived from a long term dataset of Maori ‘muttonbirder’ diaries were obtained and used as response variables in a gridded spatial model. It was found that areas of the sub-Antarctic water region best capture the variation in the chick size data. Oceanographic features including wind speed and charnock (a derived variable representing ocean surface roughness) came out as top predictor variables in these models. Previously collected GPS data demonstrates that these regions are used as “flyways” by sooty shearwaters during the breeding season. It is therefore likely that wind speeds in these flyways affect the ability of sooty shearwaters to provision for their chicks due to changes in flight dynamics. This approach was designed to utilize machine learning methodology but can also be implemented with other statistical algorithms. Furthermore, these methods can be applied to any long term time series of population data to identify important regions for a species of interest.

The role of climate and food availability on driving decadal abundance patterns of highly migratory pelagic predators in the Bay of Biscay

Within the current context of changing ecosystems, many organisms are experiencing phenological changes in the timing of migration. Here, we assessed whether the abundance patterns of two trans-equatorial migrating pelagic seabirds, the great shearwater and the sooty shearwater (Puffinus gravis and P. griseus, respectively), have changed over recent decades in the Bay of Biscay in relation to the main drivers shaping their migratory journey: climatic factors and food availability. Specifically, we studied the staging dynamic by estimating dates of arrival and departure, staging duration and abundance during a 16-year temporal window (1995-2010) based on monthly at-sea observations performed onboard a commercial ferry. Climatic effects were studied at two temporal scales: oceanic winds and global oscillations indices (North Atlantic Oscillation – NAO) that represent climate variability at short and long time scales, respectively. Based on oceanic winds, we also estimated a hypothetical cost of flying on a monthly basis considering wind speed and the angle between flight and wind direction. Our results showed that both great and sooty shearwaters were influenced by the large scale NAO index but the shape of the relationship was different, while the sooty shearwater was also influenced by food availability. Thus, each species might rely on different cues before and during their migration to adjust to optimal flying conditions and foraging grounds. Both species shape their arrival in the Bay of Biscay with periods of potential minimum flying costs, following their migration from the western to the eastern North Atlantic. We foresee that the quantification of flying costs can integrate different processes at the level of migration and provide a wider understanding of the migratory dynamic of pelagic predators within current changing ecosystems.

Comparative seabird diving physiology: first measures of haematological parameters and oxygen stores in three New Zealand Procellariiformes

Within breath-hold diving endotherms, procellariiform seabirds present an intriguing anomaly as they regularly dive to depths not predicted by allometric models. How this is achieved is not known as even basic measures of physiological diving capacity have not been undertaken in this group. To remedy this we combined time depth recorder (TDR) measurements of dive behaviour with haematology and oxygen store estimates for 3 procellariiform species (common diving petrels Pelecanoides urinatrix urinatrix; grey-faced petrels Pterodroma macro ptera gouldi; and sooty shearwaters Puffinus griseus) during their incubation phase. Among species, we found distinct differences in dive depth (average and maximal), dive duration and dives h �1 , with sooty shearwaters diving deeper and for longer than grey-faced petrels and common diving petrels. Conversely, common diving petrels dove much more frequently, albeit to shallow depths, whereas grey-faced petrels rarely dived whatsoever. Such differences in dive behaviour were reflected in haematological parameters, with sooty shearwaters having higher red blood cell counts and haematocrit (Hct) values compared to common diving and grey-faced petrels; whereas common diving petrels had significantly lower Hct but possessed higher haemoglobin concentrations per cell and greater respiratory oxygen stores than both sooty shearwaters and grey-faced petrels. Such results provide the first insights into the physiological traits underpinning procellariiform dive behaviour, and confirm the trend for deep-diving seabirds to have proportionally lower blood and respiratory oxygen stores than shallow divers.

Stable isotope values delineate the non-breeding distributions of sooty shearwaters Puffinus griseus in the North Pacific Ocean

Following breeding, sooty shearwaters Puffinus griseus leave New Zealand waters and migrate to 1 of 3 distinct areas in the North Pacific Ocean, effectively exploiting environmen- tal resources across a large proportion of this northern ocean basin. In this study, we combined electronic tracking technology with stable isotope analyses (δ 15 N and δ 13 C) of feathers grown dur- ing the non-breeding period in order to evaluate whether isotope signatures can be used to iden- tify specific non-breeding areas used by sooty shearwaters. A region to the east of Japan was utilised by the majority of tracked birds, whereas others used areas off the west coast of North America. Stable isotope values of feathers allowed the discrimination of individuals that used each of the 3 different non-breeding areas, and suggested that birds off Japan can be further separated into 'coastal' and 'offshore' groups. Our results confirm the utility of using stable isotope analysis, validated by tracking devices, as a tool to determine distribution and habitat use of a long-range oceanic migrant, the sooty shearwater. These results also highlight the resource connectivity between the northern and southern Pacific Ocean basin.

Pattern recognition in long‐term Sooty Shearwater data: applying machine learning to create a harvest index.

Rakiura Māori (New Zealand's southernmost group of indigenous peoples) have harvested the chicks of burrow-nesting Sooty Shearwaters (Tītī; Puffinus griseus) for generations. As part of the harvest process, some families have maintained annual harvest diaries, some dating back to the 1950s. We used generalized boosted regression models, a machine-learning algorithm, to calculate a harvest index that takes into account factors that could impact the numbers of birds taken on any given hunt. For predicted vs. observed values, r2 was between 0.59 and 0.90 for the nanao (first half of the season, when chicks are harvested from burrows during the day) and 0.67 and 0.88 for the rama (second half of the season, during which chicks are harvested from the surface at night). Exploration of the controlling factors of the models revealed that “day of season” plays an important role in predicting daily harvest during the second half of the season (the rama). The nightly tally in the rama peaked approximately halfway through (10–15 days in), which is probably related to the timing of birds emerging from burrows to fledge. The models also suggested that data from the rama (when chicks are 100–120 days old) may be the most suitable for long-term monitoring of populations of Sooty Shearwaters due to consistencies in calculated harvest indices between diaries. Nanao harvest indices, although less consistent, showed patterns similar to those of the rama. When comparing these data to the harvest indices calculated by general linear models by Clucas and colleagues, we found that the agreement between both indices was r2 = 0.31 and r2 = 0.59 for the nanao and rama, respectively. The use of machine learning to correct for extraneous factors (e.g., hunting effort, skill level, or weather) and to create standardized measures could be applied to other systems such as fisheries or terrestrial resource management.