Larus Dominicanus Research Articles

Kelp and dolphin gulls cause perineal wounds in South American fur seal pups (Arctocephalus australis) at Guafo Island, Chilean Patagonia.

During five reproductive seasons, we documented the presence, extent and origin of perineal wounds in South American fur seal pups (Arctocephalus australis) on Guafo Island, Northern Chilean Patagonia. The seasonal prevalence of perineal wounds ranged from 5 to 9%, and new cases were more common at the end of the breeding season (February), when pups were on average two months old and were actively expelling hookworms (Uncinaria sp). Histologically, wounds corresponded to marked ulcerative lymphoplasmacytic and histiocytic dermatitis with granulation tissue and mixed bacterial colonies. In 2015 and 2017, kelp gulls (Larus dominicanus) and dolphin gulls (Leucophaeus scoresbii) were observed picking and wounding the perineal area of marked pups. This behaviour occurred more frequently after the pups' defecation, when sea gulls engaged in consumption of pups' faeces. The affected pups usually had moderate to marked hookworm infections along with bloody diarrhoea and anaemia. Pups with severe wounds (23% of affected animals) had swollen perineal areas and signs of secondary systemic bacterial infection. We propose that seagulls on Guafo Island have learned to consume remains of blood and parasites in the faeces of pups affected by hookworm infection, causing perineal wounds during this process. We conclude that this perineal wounding is an unintentional, occasional negative effect of an otherwise commensal gull–fur seal relationship.

Status and distribution of the suborder Lari in Paraguay, including new country records

The Lari of Paraguay are poorly known and only three species in two families occur regularly (Large-billed Tern Phaetusa simplex, Yellow-billed Tern Sternula superciliaris and Black Skimmer Rynchops niger). However, recent field studies have revealed that diversity is much greater than previously thought, and several new species have been added to the country list in recent years. With many of these species being of only transient presence, the distribution and status of Paraguayan species is reviewed here including first reports of four species (Laughing Gull Leucophaeus atricilla, Franklin’s Gull Leucophaeus pipixcan, Gull-billed Tern Gelochelidon nilotica, and Whiskered Tern Chlidonias hybrida) and one subspecies (Black Skimmer Rynchops niger cinerascens). The first South American record of the Whiskered Tern Chlidonias hybrida is remarkable coming from a country in the center of the continent. Reports of three other species (Kelp Gull Larus dominicanus, Snowy-crowned Tern Sterna trudeaui and Royal Tern Thalasseus maximus) are discussed and treated as hypothetical. Basic breeding data is provided for three species (Large-billed Tern, Yellow-billed Tern and Black Skimmer), showing that clutch sizes fall within clutch size ranges of other studies.

Influence of Delipidation on Hg Analyses in Biological Tissues: A Case Study for an Antarctic Ecosystem

The use of low-polarity organic solvents is widespread in cleanup/extraction processes in order to carry compounds of interest, remove interferences and separate phases, among other uses. A large number of studies have used delipidation to remove excess of lipids to analyse carbon stable isotopes in biological tissues for trophic and behavioural ecology investigations. In this context, the primary aim of this study is to assess the influence of one delipidation process on the results of total mercury (Hg) analyses and the possible use of delipidated samples from previous analyses, such as for stable isotopes, in Hg level determination. Samples of vegetation (angiosperm, lichens and mosses), invertebrates (krill and limpets), fish (marbled and black rockcod), bird liver and eggs (Antarctic, Gentoo and Adelie penguins, kelp gull, Antarctic tern, cape petrel and giant southern petrel) and pinniped tissues (Weddell seal, crabeater seal, southern elephant seal and Antarctic fur seal) were analysed for Hg before and after delipidation by cyclohexane. The difference between the two measurements ranged individually from −63 to 136% (in the moss Sanionia uncinata) and the averages ranged from −60 to 66% (in pinniped tissues). The proportion of organic Hg, which presents considerable lipophilicity, but also high affinity for sulfhydryl groups in proteins, might be responsible for such variability. Given the limitations of our study, we think it is safe to say that delipidated samples could not be used to infer total Hg values in non-delipidated ones.

Does the closed fishing season influence the ichthyofauna consumed by Larus dominicanus?

Abstract Fish that are incidentally caught by shrimp trawling represent a predictable and abundant resource for feeding several bird species, especially for the gull Larus dominicanus. This fishing activity is subject to disruptions throughout the year during closed fishing seasons, when other fishing modalities are exercised, which can alter the composition, abundance and size of the fish bycatch. This study evaluated the influence of the restriction of fishing period of shrimp (closed season) on the diet of L. dominicanus, on the Paraná State coast. From December 2013 to August 2014, 10 pellets were collected per month in two distinct areas that have shrimp trawl fishery as the main economic activity: one continental and another in an estuarine island. In total, 920 fish were identified, divided into four families and 15 species, especially the family Sciaenidae with 11 species. There were differences in abundance and biomass of species between areas and between seasons of pre-closure, closure and post-closure. Differences for the mean total length of the species were only detected between the pre-closed and closed seasons in one area. This study evidenced the strong relationship between L. dominicanus and the shrimp trawl fishery, the species composition identified in the pellets and their respective morphometric measurements follow the same pattern of the literature for fish discarded in trawling activities.

Environmental Predictors of Seabird Wrecks in a Tropical Coastal Area.

Beached bird surveys have been widely used to monitor the impact of oil pollution in the oceans. However, separating the combined effects of oil pollution, environmental variables and methodological aspects of beach monitoring on seabird stranding patterns is a challenging task. The effects of a comprehensive set of oceanographic and climatic variables and oil pollution on seabird strandings in a tropical area of Brazil were investigated herein, using two robust and innovative methods: Generalized Linear Mixed Models and Structural Equation Modeling. We assessed strandings of four resident seabird species along 480 km of beaches divided into 11 sampling areas, between November 2010 and September 2013. We found that increasing the distance from the nearest breeding island reduce the seabird stranding events. Storm activity and biological productivity were the most important factors affecting the stranding events of brown boobies Sula leucogaster, Cabot’s terns Thalasseus acuflavidus and kelp gulls Larus dominicanus. These species are also indirectly affected by warm tropical waters, which reduce chlorophyll-a concentrations. Beach surveys are, thus, useful to investigate the mortality rates of resident species near breeding sites, where individuals are more abundant and exposed to local factors associated with at-sea mortality. In contrast, conservation actions and monitoring programs for far-ranging seabird species are needed in more distant foraging areas. Furthermore, beach monitoring programs investigating the impact of oil pollution on seabirds need to account for the effects of environmental factors on stranding patterns. The present study also demonstrated that seabirds inhabiting tropical coastal waters are sensitive to climate conditions such as adverse weather, which are expected to increase in frequency and intensity in next decades.

Anthropogenic debris in the nests of kelp gulls in South Africa

Anthropogenic debris results in detrimental interactions with many marine species. Several seabirds include debris items in their nests, which can lead to entanglement of chicks and adults, resulting in injury or death. Anthropogenic debris was found in 4–67% of kelp gull Larus dominicanus nests in seven colonies in the Western Cape, South Africa. Nests contained two types of litter: items included in the nest structure during construction (mainly ropes and straps), and regurgitated items (mainly bags and food wrappers) that probably accumulate primarily during the chick-rearing period. Debris used in nest construction was more likely to injure gulls, and was found mainly at coastal sites where there was little natural vegetation for construction. Distance to the nearest urban waste landfill significantly affected the occurrence of debris items in nests, especially dietary-derived items. The amount of debris in kelp gull nests highlights the need for improved debris management in South Africa.

Breeding records of kelp gulls in areas newly exposed by glacier retreat on King George Island, Antarctica

In recent decades, the glaciers on the Antarctic Peninsula have been rapidly retreating. Using satellite images taken during the austral summer from 1989 to 2016, we estimated the glacier pattern on King George Island in the Antarctic Peninsula, Antarctica, and found that glacier boundaries have gradually retreated. We have recorded the kelp gull nest sites in this glacier-retreat region during four breeding seasons (from 2012–2013 to 2015–2016). Satellite images and newly established kelp gull nests suggest that glacier retreat could lead to an enlarged breeding habitat for kelp gulls.

Phylogenetic Placement of a Schistosome from an Unusual Marine Snail Host, the False Limpet (Siphonaria lessoni) and Gulls (Larus dominicanus) from Argentina with a Brief Review of Marine Schistosomes from Snails

In the blood fluke family Schistosomatidae, marine snails are well known as intermediate hosts. Eight families of marine snails have thus far been reported to host schistosomes across the world, most of which have been implicated in human cercarial dermatitis (HCD) outbreaks. As part of our larger effort to define the species diversity and biology of schistosomes in Argentina, in particular their role in causing HCD, we searched in the marine pulmonate snail (Siphonaria lessoni) for a schistosome species described previously from S. lessoni from southern Argentina. Additionally, gulls (Larus dominicanus) collected from a different project locality (inland) were examined, because they are known to spend time in the intertidal regions. Schistosome sporocysts were found in S. lessoni, and a small worm fragment was retrieved from a gull. Molecular phylogenies for 28S, ITS1-5.8S-ITS2, and cox1 genes revealed that the specimens from the gull and S. lessoni grouped closely together, suggesting they are conspecifics. Also, ITS1-5.8S-ITS2 sequences suggested one of the schistosomes from S. lessoni and a schistosome from a South African penguin were also conspecifics. Further study is needed to verify if these specimens comprise a distinct marine clade within the larger avian schistosome clade that is comprised mostly of species using freshwater snail hosts. Thus far, it appears this group of marine schistosomes may be more likely found in the southern hemisphere. It is unclear if the observed distribution pattern of schistosomes in Siphonaria is a result of sampling bias and/or indicative of a specific bird-snail-schistosome association. It is clear they are sharply differentiated from the basal marine clade of avian schistosomes that includes Austrobilharzia.

Erysipelothrix rhusiopathiae isolated from gull-inflicted wounds in southern right whale calves.

Southern right whales Eubalaena australis from Peninsula Valdés, Argentina, show wounds produced by kelp gulls Larus dominicanus that feed on the whales' dorsal skin and blubber. During the 2013 whale season, several calves were reported showing kelp gull injuries with a swollen area surrounded by rhomboid-shaped raised edges. Samples from 9 calves were taken in order to establish the etiology of these rhomboid-shaped wounds; 2 calves (one living, one dead) showed gull-inflicted injuries with rhomboid-shaped edges. Samples from the dead calf were histologically characterized by the presence of dermal congestion, suppurative dermatitis and panniculitis, necrotizing vasculitis and vascular thrombosis. Erysipelothrix rhusiopathiae was detected by culture and PCR in samples from both calves. In this study we report, for the first time to our knowledge, the isolation of E. rhusiopathiae from wounds produced by gull attacks on southern right whale calves, supplying evidence that these wounds may act as an entry route for pathogens. This work provides new information about the consequences of gull-inflicted injuries for whale health.

Molecular Characterization of Extended-Spectrum-Cephalosporin-Resistant Enterobacteriaceae from Wild Kelp Gulls in South America

Extended-spectrum-cephalosporin-resistant Enterobacteriaceae are a public health concern due to limited treatment options. Here, we report on the occurrence and the molecular characteristics of extended-spectrum-cephalosporin-resistant Enterobacteriaceae recovered from wild birds (kelp gulls). Our results revealed kelp gulls as a reservoir of various extended-spectrum cephalosporinase genes associated with different genetic platforms. In addition, we report for the first time the presence of a known epidemic clone of Salmonella enterica serotype Heidelberg (JF6X01.0326/XbaI.1966) among wild birds.

Evolutionary history of the Kelp Gull (Larus dominicanus) in the southern hemisphere supported by multilocus evidence

The high dispersal ability of seabirds and the absence of geographical barriers has led to high gene flow and reduced population differentiation. Nevertheless, some species with philopatric behavior have restricted gene flow among colonies, revealing a strong population structure. Gulls show widespread colonial behavior, and are long-lived species, which make them a good model for understanding evolutionary processes in seabirds. Previous genetic studies on the Kelp Gull (Larus dominicanus) have revealed low genetic variability in mitochondrial markers but relatively high genetic variation in a nuclear marker. These observations can be explained by the occurrence of a selective sweep on mtDNA, population genetic bottlenecks or a recent origin of the species. We used microsatellite data to further investigate these hypotheses, mainly by testing for bottleneck events. Low genetic variability (H o = 0.276–0.570) was detected in Kelp Gulls. However, population genetic structure was observed among regions (Chile, Argentina and Brazil), and between continents (South America and Antarctica). The population of the Kelp Gull in South America may have differentiated due to isolation by distance (r = 0.7273, p = 0.0013), whereas the population in the Antarctic seems to be isolated by non-physical barriers. Bottleneck events were detected in 6 out of 14 colonies studied. These colonies are at the limits of the distribution of the Kelp Gull, and thus experience harsh survival conditions. We believe that the Kelp Gull has a complex history in the southern hemisphere, with a recent origin, followed by bottlenecks and then population expansion. Thus, the genetic diversity found in Kelp Gull is similar to that observed for other species of Laridae.

Plastic ingestion by a generalist seabird on the coast of Uruguay

We analyzed plastic ingestion by Kelp Gull (Larus dominicanus) from 806 pellets collected between 2011 and 2013. Employing a Raman spectroscopy, we characterized those polymers used to produce the plastics ingested. Debris was recorded in 143 pellets (%FO=17.7%, n=202, 92.58g). Plastic was found in 119 pellets (%FO=83%) and non-plastic occurred in 56 pellets (%FO=39%). The most important debris category was plastic film with 55.3% (n=79). Plastic bags were observed in 19 pellets (%FO=2.4%, weight=25.02g). Glass was the second most important component (%FO=18.9%) followed by plastic fragments (%FO=17.8%). Plastic debris represented the 65.3% of the debris fragments (n=132, weight=58.84g), and was composed by polyethylene (52%), polypropylene (26%), polyamide (12%), polystyrene (6%), polyvinyl chloride (2%), and polyethylene terephthalate (2%). How plastics were obtained by gulls and the effects on individuals are discussed, as well as environmental considerations about plastic pollution on coastal environments.

Distribution and Trends in Kelp Gull (Larus dominicanus) Coastal Breeding Populations in South America

In South America, Kelp Gulls (Larus dominicanus) breed from Chilean Tierra del Fuego north to Rio de Janeiro, Brazil, on the Atlantic coast and to Piura, Peru, on the Pacific coast. This review presents the first synthesis of information on the distribution and size of Kelp Gull colonies at the country level in coastal environments of Uruguay, Chile and Peru; provides an update on the breeding situation of the species in Brazil and Argentina; and allows the first evaluation of the overall coastal breeding population in South America. The breeding population in South America is now estimated to number at least 160,000 pairs. The largest population (at least 106,000 breeding pairs) is found in Argentina. Colonies of more than 1,000 pairs are uncommon. Population trends differed among coastal sectors, and important increases in numbers and formation of new colonies were only observed in Argentina. Available information suggests that predictable and abundant anthropogenic food subsidies, such as fishery discards and urban waste, are key factors contributing to the population growth in some coastal sectors. There is no strong evidence that Kelp Gulls are currently expanding their breeding range. However, given the population expansion in some areas and the potential conflicts with humans, ongoing monitoring efforts and population evaluations are necessary as they will provide the information required to support management decisions.

Recent Trends of the Kelp Gull (Larus dominicanus) in South Africa

Abstract. South Africa's population of Kelp Gulls (Larus dominicanus vetula) numbered about 10,000 pairs during 1976/1977–1980/1981, increased to 21,000 pairs from 2000/2001–2004/2005 and then decreased to 17,500 pairs from 2009/2010–2013/2014. The increase in the late 20th century and the decrease in the early 21st century were mainly attributable to large increases and decreases in numbers breeding at islands off the west coast of South Africa. The increases followed cessation of controls on Kelp Gulls at the islands in the 1970s and were associated with supplementary food provided by fisheries and landfill sites, whereas the decreases were influenced by substantial predation of chicks by Great White Pelicans (Pelecanus onocrotalus). The decreases of Kelp Gulls at islands off the west coast of South Africa in the early 21st century were offset to some extent by an increase in numbers breeding on mainland sites, especially around greater Cape Town and along the south coast. The proportion of Kelp Gulls b...

GUIDELINES FOR MANAGING SEABIRDS IN THE ARVOREDO MARINE BIOLOGICAL RESERVE, SOUTHERN BRAZIL

Seabirds usually need productive waters and respond differently to environmental changes according to the oceanographic domain where they occur. The Arvoredo Marine Biological Reserve protects part of an important ecological region in Brazil and shelters substantial marine biodiversity. Here we studied seabird richness and abundance at this protected area to verify what kind of monitoring and managing protocols are needed for future conservation actions. We surveyed the Reserve’s islands and surrounding sea from the autumn 2010 to the autumn 2012. We also considered historical data from literature on seabird colonies to access specific issues related to management actions. Most of 14 surveyed species were migratory, rare, and recorded during winter. The Kelp Gull ( Larus dominicanus ) was dominant and its abundance pattern alternated with those of the other species along seasons. Deserta Island is an important breeding site and Gale Islets is an important stopover site at the Reserve. Few places along the Brazilian coastline support breeding colonies such as the ones in the Arvoredo Marine Biological Reserve. However, the Reserve needs seabird active management to fulfill its purpose of protecting marine biodiversity. Breeding success must be considered as an indicator for intervention and control of predators in the Reserve. The effects of climate changes and overfishing near the Reserve affect the seabirds therefore managers should join a large-scale integrated coastal management and marine spatial planning. A long-term monitoring protocol at-sea and in the colonies using new technologies also can help in this process.

GENETICS AND DEMOGRAPHY OF KELP GULLS IN PATAGONIA

The Kelp Gull (Larus dominicanus), a common seabird in coastal Patagonia, has recently increased in overall abundance and distribution, creating some concerns for the protection and conservation of other native, threatened species. We combined genetic and demographic data of four large Kelp Gull colonies distributed along 1800 km of the northern Patagonian coast of Argentina to further understand patterns of population growth and migration of the species. DNA analysis of variable intron sequences of two separate genes (myelin proteolipid protein, β-fibrinogen) revealed similar intra-colony levels of DNA sequence diversity. Pairwise FST comparisons revealed significant differentiation of the northernmost colony, Islote La Pastosa, from the two southern colonies, Punta Tombo and Isla Vernaci Sudoeste (p < 0.05). Indirect estimates of gene flow suggest significant mixing among colonies (Nm > 6). Demographic estimates revealed that Islote La Pastosa showed an increase in the number of breeding individuals over time (λ = 1.075), representing an area of potential population expansion. This is consistent with previous studies that have suggested that the demographic connectivity among Kelp Gull colonies in Patagonia may follow a source-sink dynamics, where growth rates of growing colonies are fuelled by the immigration of individuals from nearby colonies. The observed pattern also reflects the overall expansion of the species in the Patagonian region. This study suggests that proper management strategies for the Kelp Gull should take into account the genetic and demographic dynamics of this species.

System dynamics modelling of the Endangered African penguin populations on Dyer and Robben islands, South Africa

African penguins (Spheniscus demersus) in South Africa have been subject to rapid decline in the 20th century and are currently listed as “endangered” on the IUCN Red List. A stochastic, stage-specific system dynamics model with spatial components was developed to investigate the interaction of multiple pressures on penguin population development, and originally applied to study conservation management options for the penguin colony at Robben Island, Table Bay, South Africa. We here present an extension of the model to the nearby colony at Dyer Island. The modelled population was found to be strongly dominated by the effects of Cape fur seal (Arctocephalus pusillus pusillus) predation and immature emigration, which appear to be key drivers behind current declines in population numbers at this colony. Chronic low-level oiling also had a consistent impact despite ongoing mitigation measures, while kelp gull predation had a lower effect than expected. At current low population size, the pressure from either seal predation or immature emigration seems sufficient to mask any beneficial effects to penguins from possible improvements in available food biomass (e.g., from fishery restrictions). Results suggest that conservation management at this colony should focus on regular culling of predating seals combined with improving availability of prey (thus discouraging emigration) both in the foraging range of breeding penguins and in their general foraging area. Our findings demonstrate the use of site-specific scenario tools to explore conservation strategies in data-poor management situations.

Preliminary assessment of contaminants in the sediment and organisms of the Swartkops Estuary, South Africa

Urban estuaries are susceptible to metal and organic pollution, yet most remain understudied in South Africa with respect to the presence, concentrations and distribution of contaminants. Metal and organic chemical concentrations were assessed in sediment and organisms from different trophic levels in the lower reaches of the Swartkops Estuary. Species sampled included Upogebia africana (Malacostraca: Upogebiidae), Gilchristella aestuaria (Clupeidae), Psammogobius knysnaensis (Gobiidae), Mugil cephalus (Mugilidae), Lichia amia (Carangidae), Argyrosomus japonicus (Sciaenidae), Pomadasys commersonnii (Haemulidae) and Larus dominicanus (Avis: Laridae). This study is one of the most comprehensive studies to date assessing pollution levels in a food web in estuaries in South Africa. Due to biomagnification, higher concentrations of Arsenic, Lead, Mercury and Cadmium were found in the juveniles stages of popular angling fishes. High concentrations of Cadmium and Arsenic were recorded in the liver of L. amia, A. japonicus and P. commersonnii which exceed international quality food guidelines. Eggs from the gull, L. dominicanus, showed detectable concentrations of PCBs.

Increased Wounding of Southern Right Whale (Eubalaena australis) Calves by Kelp Gulls (Larus dominicanus) at Península Valdés, Argentina.

At least 626 southern right whale (Eubalaena australis) calves died at the Península Valdés calving ground, Argentina, between 2003 and 2014. Intense gull harassment may have contributed to these deaths. In the 1970s, Kelp Gulls (Larus dominicanus) began feeding on skin and blubber pecked from the backs of living right whales at Valdés. The frequency of gull attacks has increased dramatically over the last three decades and mother-calf pairs are the primary targets. Pairs attacked by gulls spend less time nursing, resting and playing than pairs not under attack. In successive attacks, gulls open new lesions on the whales’ backs or enlarge preexisting ones. Increased wounding could potentially lead to dehydration, impaired thermoregulation, and energy loss to wound healing. The presence, number and total area of gull-inflicted lesions were assessed using aerial survey photographs of living mother-calf pairs in 1974–2011 (n = 2680) and stranding photographs of dead calves (n = 192) in 2003–2011. The percentage of living mothers and calves with gull lesions increased from an average of 2% in the 1970s to 99% in the 2000s. In the 1980s and 1990s, mothers and calves had roughly equal numbers of lesions (one to five), but by the 2000s, calves had more lesions (nine or more) covering a greater area of their backs compared to their mothers. Living mother-calf pairs and dead calves in Golfo Nuevo had more lesions than those in Golfo San José in the 2000s. The number and area of lesions increased with calf age during the calving season. Intensified Kelp Gull harassment at Península Valdés could be compromising calf health and thereby contributing to the high average rate of calf mortality observed in recent years, but it cannot explain the large year-to-year variance in calf deaths since 2000.

HEMATOLOGIC AND BIOCHEMICAL PARAMETERS OF KELP GULLS (LARUS DOMINICANUS) CAPTURED IN THE CITY OF TALCAHUANO, CHILE

In order to provide tools for future health-based monitoring programs, we developed reference intervals for hematology and plasma biochemistry and partitioned data for sex and season (winter and autumn). Ninety-one physically healthy kelp gulls (Larus dominicanus) were sampled in the city of Talcahuano, Chile, during winter (July-September) of 2007, autumn (April-June) and winter of 2008, and autumn of 2009. After blood sampling, the kelp gulls were euthanized by cervical dislocation. Packed cell volume (PCV), hemoglobin, total plasma protein (TPP), and complete blood count were performed. Alanine amino transferase, gamma-glutamyl transpeptidase, lactate dehydrogenase, alkaline phosphatase (ALP), creatinine, urea, calcium, phosphorus, and uric acid were analyzed. No significant differences were found between sexes (P>0.05). When a comparison was made between the two seasons, the values of PCV, TPP, white blood cell, heterophils, eosinophils, and monocytes were significantly higher in winter than in autumn (P<0.05) while and urea and uric acid concentrations were higher in autumn. Heterophils were the predominant circulating leukocyte for all birds. There was no significant difference in body condition between autumn and winter nor between sexes. Body condition showed a significant relationship with TPP and basophil concentration and ALP activity.