Global assessment of marine plastic exposure risk for oceanic birds

Plastic pollution is distributed patchily around the world's oceans. Likewise, marine organisms that are vulnerable to plastic ingestion or entanglement have uneven distributions. Understanding where wildlife encounters plastic is crucial for targeting research and mitigation. Oceanic seabirds, particularly petrels, frequently ingest plastic, are highly threatened, and cover vast distances during foraging and migration. However, the spatial overlap between petrels and plastics is poorly understood. Here we combine marine plastic density estimates with individual movement data for 7137 birds of 77 petrel species to estimate relative exposure risk. We identify high exposure risk areas in the Mediterranean and Black seas, and the northeast Pacific, northwest Pacific, South Atlantic and southwest Indian oceans. Plastic exposure risk varies greatly among species and populations, and between breeding and non-breeding seasons. Exposure risk is disproportionately high for Threatened species. Outside the Mediterranean and Black seas, exposure risk is highest in the high seas and Exclusive Economic Zones (EEZs) of the USA, Japan, and the UK. Birds generally had higher plastic exposure risk outside the EEZ of the country where they breed. We identify conservation and research priorities, and highlight that international collaboration is key to addressing the impacts of marine plastic on wide-ranging species.

Arthropod Predation of Vertebrates Structures Trophic Dynamics in Island Ecosystems

AbstractOn isolated islands, large arthropods can play an important functional role in ecosystem dynamics. On the Norfolk Islands group, South Pacific, we monitored the diet and foraging activity of an endemic chilopod, the Phillip Island centipede (Cormocephalus coynei), and used a stable isotope mixing model to estimate dietary proportions. Phillip Island centipede diet is represented by vertebrate animals (48%) and invertebrates (52%), with 30.5% consisting of squamates, including the Lord Howe Island skink (Oligosoma lichenigera) and Günther's island gecko (Christinus guentheri); 7.9% consisting of black-winged petrel (Pterodroma nigripennis) nestlings; and 9.6% consisting of marine fishes scavenged from regurgitated seabird meals. Centipede predation was the principal source of petrel nestling mortality, with annual rates of predation varying between 11.1% and 19.6% of nestlings. This means that 2,109-3,724 black-winged petrel nestlings may be predated by centipedes annually. Petrels produce a single offspring per year; therefore, predation of nestlings by centipedes represents total breeding failure for a pair in a given year. Our work demonstrates that arthropods can play a leading role in influencing vertebrate reproductive output and modifying trophic structures and nutrient flow in island ecosystems.

Assessing multiple threats to seabird populations using flesh-footed shearwaters Ardenna carneipes on Lord Howe Island, Australia as case study

Globally, seabird populations have been in decline due to multiple threats throughout their range. Separating simultaneous pressures is challenging and can require significant amounts of data over long periods of time. We use spatial contrasts to investigate the relative importance of several drivers for the purported decline in a species listed as in decline as an example species, the Flesh-footed shearwater (Ardenna carneipes). On Lord Howe Island in the Tasman Sea, Australia, this seabird suffers from habitat loss due to housing development, intensive mortality in fisheries, plastic ingestion, and roadkill due to vehicular traffic on its breeding island. We repeated a quantitative survey of the population to ascertain whether the decline previously reported had continued and to evaluate the purported mortality sources (Reid et al. in PLoS ONE 8(4):e58230, 2013, Lavers et al. in Global Ecol Conserv 17:e00579, 2019). We measured burrow density, area of occurrence, occupancy and breeding success, integrating them with previous surveys using a Bayesian statistical model to generate longer term estimates of demographic rates. We used spatial patterns to test whether mortality on roads or proximity to human habitation was influencing population demographics. In contrast to predictions, we found the population had stabilised or increased. Characteristics such as burrow occupancy and breeding success showed little pattern, with weak evidence for impacts from road mortality and housing development. Such a data-rich approach is substantially more informative and can better support seabird conservation and management efforts does require more field-time and additional equipment than most contemporary surveys, the data is substantially more informative and can better clarify the results of efforts in seabird conservation and management.

Phylogenetic affinities of the Fregetta storm-petrels are not black and white

The Fregetta storm-petrels generally are regarded to comprise two species: black-bellied storm-petrels F. tropica (monotypic) breed at Antarctic and sub-Antarctic islands (46-63°S), and white-bellied storm-petrels F. grallaria breed at south temperate islands (28-37°S), with four recognized subspecies. Confusion surrounds the status of birds at Gough Island (40°S), central South Atlantic, which have been attributed usually to a white-bellied form of black-bellied storm-petrel F. t. melanoleuca. We use cytochrome b and nuclear β-fibrinogen gene sequences to show that F. t. melanoleuca are present during the breeding season at Gough and islands in the nearby Tristan da Cunha archipelago (37°S), exhibiting limited divergence from F. t. tropica. We also show that there is greater diversity among F. grallaria populations, with eastern South Pacific F. g. segethi and F. g. titan differing by c. 0.011, and both differing from western South Pacific nominate F. g. grallaria by c. 0.059. The Tristan archipelago supports a population of F. grallaria closely allied to the nominate form, as well as a distinct form identified as F. g. leucogaster. Further research is needed to assess how F. grallaria and F. tropica segregate in sympatry at Tristan and Gough, and why this is the only location where both species have white-bellies.

High prevalence of Salmonella and IMP-4-producing Enterobacteriaceae in the silver gull on Five Islands, Australia

OBJECTIVES

The objective of this study was to investigate the silver gull as an indicator of environmental contamination by salmonellae and carbapenemase-producing Enterobacteriaceae (CPE) in south-east Australia.

METHODS

A total of 504 cloacal samples were collected from gull chicks at three nesting colonies in New South Wales, Australia [White Bay (n = 144), Five Islands (n = 200) and Montague Island (n = 160)] and were examined for salmonellae and CPE. Isolates were tested for carbapenemase genes and susceptibility to 14 antibiotics. Clonality was determined by PFGE and MLST. Genetic context and conjugative transfer of the carbapenemase gene were determined.

RESULTS

A total of 120 CPE of 10 species, mainly Escherichia coli (n = 85), carrying the gene blaIMP-4, blaIMP-38 or blaIMP-26 were obtained from 80 (40%) gulls from Five Islands. Thirty percent of birds from this colony were colonized by salmonellae. Most isolates contained the gene within a class 1 integron showing a blaIMP-4-qacG-aacA4-catB3 array. The blaIMP gene was carried by conjugative plasmids of variable sizes (80-400 kb) and diverse replicons, including HI2-N (n = 30), HI2 (11), A/C (17), A/C-Y (2), L/M (5), I1 (1) and non-typeable (6). Despite the overall high genetic variability, common clones and plasmid types were shared by different birds and bacterial isolates, respectively.

CONCLUSIONS

Our data demonstrate a large-scale transmission of carbapenemase-producing bacteria into wildlife, likely as a result of the feeding habits of the birds at a local waste depot. The isolates from gulls showed significant similarities with clinical isolates from Australia, suggesting the human origin of the isolates. The sources of CPE for gulls on Five Islands should be explored and proper measures applied to stop the transmission into the environment.

Epidemiology and molecular phylogeny of Babesia sp. in Little Penguins Eudyptula minor in Australia

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We examined blood smears from 263 wild little penguins in southeastern Australia.

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Babesia sp. was detected in penguins in New South Wales, Victoria and Tasmania.

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True prevalence is estimated between 3.4% and 4.5%.

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Babesia sp. from little penguins is closely related to B. poelea and B. uriae.

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Babesia infections were assymptomatic.

Blood parasites are potential threats to the health of penguins and to their conservation and management. Little penguins Eudyptula minor are native to Australia and New Zealand, and are susceptible to piroplasmids (Babesia), hemosporidians (Haemoproteus, Leucocytozoon, Plasmodium) and kinetoplastids (Trypanosoma). We studied a total of 263 wild little penguins at 20 sites along the Australian southeastern coast, in addition to 16 captive-bred little penguins. Babesia sp. was identified in seven wild little penguins, with positive individuals recorded in New South Wales, Victoria and Tasmania. True prevalence was estimated between 3.4% and 4.5%. Only round forms of the parasite were observed, and gene sequencing confirmed the identity of the parasite and demonstrated it is closely related to Babesia poelea from boobies (Sula spp.) and B. uriae from murres (Uria aalge). None of the Babesia-positive penguins presented signs of disease, confirming earlier suggestions that chronic infections by these parasites are not substantially problematic to otherwise healthy little penguins. We searched also for kinetoplastids, and despite targeted sampling of little penguins near the location where Trypanosoma eudyptulae was originally reported, this parasite was not detected.

Conservation of the endangered Gould's Petrel Pterodroma leucoptera leucoptera

The only population of Gould's Petrel Pterodroma leucoptera leucoptera has declined substantially during the last few decades. Adult mortality has been high, and has exceeded potential recruitment. Breeding success has been low. Entanglement in the sticky fruits of the Birdlime Tree Pisonia umbellifera and predation by Pied Currawongs Strepera graculina and Australian Ravens Corvus coronoides have been the major causes of petrel mortality on land. Experimental management actions aimed at ameliorating these threats were implemented, and their efficacy assessed. The removal of Pisonia and the control of avian predators dramatically lessened the mortality of Gould's Petrels ashore on Cabbage Tree Island. Instigation of these management actions in 1993 was coincident with a 68% rise in the number of birds brooding eggs in mid-December. Further small increases in the breeding population occurred in subsequent years. Management of the colony was also coincident with a substantial increase in breeding success (up from 25% to 45%). Breeding success increased to 59% in the 1994?95 season, but declined to 26% during 1995?96. Prior to management of the colony, an average of 30 birds fledged per annum (range 23?40; n= 4); after management, this rose to 167 per annum (range 105?233; n= 3). Management of the colony appears the most likely cause of this turnaround, but the possibility of it being due to extraneous factors such as weather or oceanographic perturbations cannot be excluded. The threats posed by Pisonia umbellifera and avian predators were, together, sufficient to account for the decline of Gould's Petrel. The demonstration that these two threatening processes can be ameliorated successfully suggests a high potential for recovery of the species.

The status of Gould's petrel, Pterodroma leucoptera leucoptera, on Cabbage Tree Island, New South Wales

Gould's petrel, Pterodroma leucoptera leucoptera, breeds only on Cabbage Tree Island, New South Wales. Annual surveys to estimate the size of the breeding population and the reproductive output were conducted between 1989 and 1992. Annual estimates of the total number of pairs breeding in the two gullies containing the main population were between 122 +/- 20 (s.e.) and 202 +/- 26. Breeding success was less than 20% between 1989 and 1991, but rose to 24.7% in 1992. This marginal improvement may be the result of management action undertaken to reduce mortality of breeding adults and fledglings. The total population is estimated to have declined from 2004 (95% confidence limits: 1464,3185) in 1970 to 1479 (1250,1815) in 1992, a decline of 26% in 22 years. The reasons for this decline are unclear.

Methods for population control within a silver gull colony

Silver gulls can threaten the welfare of humans and other wildlife. Current superabundant gull numbers should be managed to reduce this risk. Denying gulls access to food at artificial sites, combined with direct population control, may reduce silver gull numbers in the long term. Control measures implemented at gull colonies overseas were trialled. Human disturbance in the colony associated with routine visits to study plots led to reduced nesting density. Egg-pricking reduced nesting success; it did not induce adults to incubate for extended periods even though gulls were recorded sitting on nonviable (although not pricked) eggs for up to 76 days. Removal of eggs from nests within experimental plots did not affect overall nesting success for these plots. Habitat modification, by mowing of long grass at the colony site prior to the commencement of breeding, decreased both the density of nests in mowed areas and nesting success. Selective culling of breeding adults from experimental plots was effective in reducing population size immediately and suppressed nesting by other individuals that attempted to breed later in the breeding season. The combination of habitat modification, culling and human disturbance reduced breeding success at colonies.

Sexing and aging silver gulls, Larus novaehollandiae

Measurements of bill size differed between gulls from three widely separated Australian regions, suggesting that there are a number of different subpopulations. When assigning an individual to a sex, a geographical locality factor should be incorporated into the discriminant model. Bill colour may be a useful tool for ageing gulls and detailed colour categories have been identified which could be used to define relative ages. Free-flying gulls are here ascribed to one of seven categories. Colour categories may not be universal; therefore, the population should be considered region by region.

Silver gull breeding at two colonies in the Sydney-Wollongong regio, Australia

Silver gulls have increased in abundance in Sydney-Wollongong this century. Both the number of colonies and their sizes have grown. The largest colony of 43 000-50000 pairs is on Big I., off Wollongong. Breeding was compared at this colony with that at a satellite colony on artificial structures in Rozelle Bay, Sydney Harbour. Breeding occurred from July to February at Big I., a lengthening of the season since the 1960s. At Rozelle Bay, breeding occurred almost all year round. Egg and clutch size varied within and between years at Big I. First-eggs of clutches, laid during the first breeding peak, were significantly larger than those laid later in each breeding season. The size of third-eggs in clutches differed between years. It is proposed that these disparities were a result of differences in food availability between years. Clutch sizes were significantly larger during the first breeding peak than later clutches of each season. Clutch size was larger at Rozelle Bay. Variation in clutch size was linked to quality of individuals and food availability. Breeding success at colonies was low, indicating that carrying capacities have been reached.

Breeding and movements of wing-tagged silver gulls (Larus novaehollandiae) at the largest colony in New South Wales

Wing tags were used in preference to colour/metal band combinations to increase sighting frequency of silver gulls. Wing tags did not affect return rate of breeding adults to the colony compared with banded gulls. Approximately one-third of gulls lost their nests following wing-tagging. There were no instances of double-brooding with fledging success from both attempts. A total of 42% of adults that returned and bred, nested more than once in a season. Up to 4 clutches were produced by pairs within a season. Successful raising of young typically occurred from the first brood of the season. Successful breeders usually nested only once in any one season. In all, 19% of pairs successfully fledged young, but the percentage of young fledged from the number of eggs laid was much lower (5.3%). Nest sites were rarely repeatedly used by the same nesting pair. Individuals moved considerable distances between successive nesting sites within and between seasons. Fidelity to colony was 68% and to mate 22%; these estimates are lower than those from other colonies.