Tern Thalasseus Research Articles

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.

Trophic ecology drives contaminant concentrations within a tropical seabird community

To support environmental management programs, there is an urgent need to know about the presence and understand the dynamics of major contaminants in seabird communities of key marine ecosystems. In this study, we investigated the concentrations and trophodynamics of trace elements in six seabird species and persistent organic pollutants (POPs) in three seabird species breeding on Grand Connétable Island (French Guiana), an area where the increase in human population and mining activities has raised concerns in recent years. Red blood cell Hg concentrations in adults were the highest in Magnificent frigatebirds Fregata magnificens (median: 5.6 μg g−1 dw; range: 3.8–7.8 μg g−1 dw) and lowest in Sooty terns Onychoprion fuscatus (median: 0.9 μg g−1 dw; range: 0.6–1.1 μg g−1 dw). Among POPs, dichlorodiphenyldichloroethylene (p,p’-DDE) was the most abundant compound in plasma of Cayenne terns Thalasseus sandvicensis (median: 1100 pg g−1 ww; range: 160 ± 5100 pg g−1 ww), while polychlorinated biphenyls (PCBs) were the most abundant compound class in plasma of Magnificent frigatebirds (median: 640 pg g−1 ww; range 330 ± 2700 pg g−1 ww). While low intensity of POP exposure does not appear to pose a health threat to this seabird community, Hg concentration in several adults Laughing gulls Leucophaeus atricilla and Royal terns Thalasseus maximus, and in all Magnificent frigatebirds was similar or higher than that of high contaminated seabird populations. Furthermore, nestling red blood cells also contained Hg concentrations of concern, and further studies should investigate its potential health impact in this seabird community. Differences in adult trophic ecology of the six species explained interspecific variation in exposure to trace element and POPs, while nestling trophic ecology provides indications about the diverse feeding strategies adopted by the six species, with the consequent variation in exposure to contaminants.

First report and breeding record of the Chinese Crested Tern Thalasseus bernsteini on the Korean Peninsula

The Chinese Crested Tern Thalasseus bernsteini is a critically endangered species (as designated by the IUCN (International Union for Conservation of Nature and Natural Resources). This report expands the known breeding grounds of these birds eastward. An individual of the Chinese Crested Tern was first observed at an uninhabited island of Jeollanam-do in Korea on April 28, 2016. On May 9, 2016 five Chinese Crested Terns (consisting of 2 breeding pairs and a single bird) were observed. Nests from the breeding pairs were found, at a distance of 0.6 m from each other; each pair was observed incubating one egg in the nest. To our knowledge, this is the easternmost record of breeding grounds for the Chinese Crested Tern.

When morphology is not reflected by molecular phylogeny: the case of three ‘orange-billed terns’ Thalasseus maximus, Thalasseus bergii and Thalasseus bengalensis (Charadriiformes: Laridae)

In order to elucidate genetic structure within the royal tern Thalasseus maximus, genetic analyses and phylogenetic reconstructions were performed on royal terns Thalasseus maximus albididorsalis from the West African breeding population and compared with sequences from American populations Thalasseus maximus maximus. The analysis shows that royal tern as currently defined is a paraphyletic species: West African royal tern is genetically distinct from American breeding populations of the nominate subspecies and forms part of a genetic cluster with lesser crested terns Thalasseus bengalensis (of all subspecies) and greater crested terns Thalasseus bergii. This represents the first published analysis of the genetic relationship between the two subspecies of royal terns, suggests that the West African population should be treated as a distinct species, and provides support to previous studies suggesting that morphological and genetic similarities are poorly correlated in the genus Thalasseus. Conservation and taxonomic implications are discussed.

The avifauna of Cartier Island Commonwealth Marine Reserve, north-western Australia

Cartier Island and the surrounding reef is an isolated Australian Territory situated in the Timor Sea. Little is known about the avifauna of the reef system and the adjacent waters. Here we summarise all known ornithological records from the Island and detail the results of twice-annual bird surveys conducted within the Cartier Island Commonwealth Marine Reserve between 2010 and 2014. By the conclusion of the surveys, a total of 34 bird species had been recorded within the Reserve. The Crested Tern Thalasseus bergii was shown to breed on the Island in small numbers. Several additional species of seabird and small numbers of shorebirds are regular visitors. Most other species occur as occasional visitors or vagrants.

Migration flyway of the Mediterranean breeding Lesser Crested Tern Thalasseus bengalensis emigratus

The Lesser Crested Tern Thalasseus bengalensis emigratus breeding population in the Mediterranean is found exclusively in Libya, on the two coastal islands of Gara and Elba and one wetland on the mainland coast at Benghazi. In order to improve knowledge of the species migration to wintering quarters in West Africa, a ringing programme was conducted from 2006–2008 and 2009–2012. From a total of 1 354 nestlings ringed using metal and/or colour rings, 64 were recovered along their flyway and in their wintering range, representing 6.9% of birds ringed with both colour and metal rings. This provided the opportunity to collect information on post-natal movements (staging and wintering ranges), breeding philopatry and recruitment, in addition to a preliminary estimate of their migration journey duration. This paper indicates sighting and recovery distributions in space and time, highlighting the important areas for the species during its journey between breeding and wintering sites. The findings indicate that several areas where ringed terns stop-over during pre- and post-breeding migration journeys are not protected, causing an additional threat to their survival, as some wintering areas are also not protected. Conservation of this highly localised and threatened population needs not only to address protection at breeding sites but also at migratory stop-overs and wintering strongholds.

Dietary studies in birds: testing a non‐invasive method using digital photography in seabirds

Summary Dietary studies give vital insights into foraging behaviour, with implications for understanding changing environmental conditions and the anthropogenic impacts on natural resources. Traditional diet sampling methods may be invasive or subject to biases, so developing non‐invasive and unbiased methods applicable to a diversity of species is essential. We used digital photography to investigate the diet fed to chicks of a prey‐carrying seabird and compared our approach (photo‐sampling) to a traditional method (regurgitations) for the greater crested tern Thalasseus bergii. Over three breeding seasons, we identified >24 000 prey items of at least 48 different species, more than doubling the known diversity of prey taken by this population of terns. We present a method to estimate the length of the main prey species (anchovy Engraulis encrasicolus) from photographs, with an accuracy <1 mm and precision ~ 0·5 mm. Compared to regurgitations at two colonies, photo‐sampling produced similar estimates of prey composition and size, at a faster species accumulation rate. The prey compositions collected by two researchers photo‐sampling concurrently were also similar. Photo‐sampling offers a non‐invasive tool to accurately and efficiently investigate the diet composition and prey size of prey‐carrying birds. It reduces biases associated with observer‐based studies and is simple to use. This methodology provides a novel tool to aid conservation and management decision‐making in the light of the growing need to assess environmental and anthropogenic change in natural ecosystems.

Pulau Ling: an important seabird hotspot on the east coast of Peninsular Malaysia

Pulau Ling is a small rocky island located to the south of Pulau Redang, forming with other southeast small islands, the Redang Archipelago, in the state of Terengganu, Malaysia. The island was highlighted in the early 1950s as an important seabird site, although little was then known on the status of seabirds on the island. Field visits were made between May 2015 and September 2015 to assess the importance of this small island to seabird species. Four tern species were identified: two of them, black-naped tern Sterna sumatrana and bridled tern Onychoprion anaethetus, were found to breed there, while the other two species, great crested tern Thalasseus bergii and roseate tern Sterna dougallii were found to use the island as a stopover site without any evidence of breeding. Furthermore, the Pacific Eastern Reef egret Egretta sacra (the black morph), was also found to breed on the island. Other species encountered included white-bellied sea eagle Haliaeetus leucogaster (recorded once in June 2015, soaring over the island). These preliminary data show the importance of such small rocky outcrops for tropical breeding and migrating seabirds, where food availability and lack of disturbance may be the two main drivers for diversity and survival.

Variation in Population Synchrony in a Multi-Species Seabird Community: Response to Changes in Predator Abundance.

Ecologically similar sympatric species, subject to typical environmental conditions, may be expected to exhibit synchronous temporal fluctuations in demographic parameters, while populations of dissimilar species might be expected to show less synchrony. Previous studies have tested for synchrony in different populations of single species, and those including data from more than one species have compared fluctuations in only one demographic parameter. We tested for synchrony in inter-annual changes in breeding population abundance and productivity among four tern species on Coquet Island, northeast England. We also examined how manipulation of one independent environmental variable (predator abundance) influenced temporal changes in ecologically similar and dissimilar tern species. Changes in breeding abundance and productivity of ecologically similar species (Arctic Sterna paradisaea, Common S. hirundo and Roseate Terns S. dougallii) were synchronous with one another over time, but not with a species with different foraging and breeding behaviour (Sandwich Terns Thalasseus sandvicensis). With respect to changes in predator abundance, there was no clear pattern. Roseate Tern abundance was negatively correlated with that of large gulls breeding on the island from 1975 to 2013, while Common Tern abundance was positively correlated with number of large gulls, and no significant correlations were found between large gull and Arctic and Sandwich Tern populations. Large gull abundance was negatively correlated with productivity of Arctic and Common Terns two years later, possibly due to predation risk after fledging, while no correlation with Roseate Tern productivity was found. The varying effect of predator abundance is most likely due to specific differences in the behaviour and ecology of even these closely-related species. Examining synchrony in multi-species assemblages improves our understanding of how whole communities react to long-term changes in the environment and suggests that changes in predator abundance may differentially affect populations of sympatric seabird species.

Egg morphology of Swift Terns in South Africa

Morphology of Swift Tern Thalasseus bergii bergii eggs was examined on Robben Island, South Africa. A recently formed colony was found abandoned en masse, probably following human disturbance, and 146 freshly laid eggs were collected. The mean±SD nest density was 7±2.5 nests m−2 and 3% of nests contained two eggs. Eggs ranged in shape from oval to pyriform and displayed black markings (blotched, streaked, scrawled or speckled) overlaying the eggs’ colour. The mean length and width of a sample of 105 eggs was 62.2 mm (56.3–66.9 mm) and 42.3 mm (39.8–45.3 mm), respectively. All collected eggs were weighed and the mean mass was 57.9±3.72 g. Estimated volume of eggs was calculated to be 56.3±3.74 cm3. This is the first report of mass measurements obtained from freshly laid eggs Swift Tern eggs and provides insight on egg morphology, for which knowledge is limited for this species.

Intra-specific plasticity in parental investment in a long-lived single-prey loader

Seabirds exhibit considerable behavioural flexibility in foraging investment in order to meet the nutritional needs of their chicks during variable environmental conditions. Although regulation of offspring provisioning is generally thought to be related to species-specific constraints imposed by central place foraging, some studies suggest different responses within the same species linked to local differences in foraging conditions. Under adverse conditions, seabirds are expected to be less flexible because they must secure their own survival chances first before investing in current reproduction. Short-ranging single-prey loaders are expected to show large intra-specific variation in time spent on foraging because their mode of foraging is energetically expensive, and because they face restricted possibilities to increase the numerical prey input to the colony compared to multiple prey loaders. In this study, we examined if and how the single-prey loading Sandwich Tern Thalasseus sandvicensis varies colony attendance based on the nutritional status of their chick as well as parental body condition in two study colonies. The proportion of time that a chick was left unattended at the colony negatively correlated with chick body condition, suggesting that the parents tried to counterbalance poor feeding conditions by investing more time in foraging. Energy transport rates to the chicks (corrected for time spent away from the colony) and body condition of the chicks were similar in both colonies. However, at Zeebrugge, where adults were in poor body condition, parental non-attendance was much lower than on Griend, even when chicks were in poor condition. Still, our results suggest that parental nest non-attendance in Sandwich Terns is merely a corrective response to food loss to kleptoparasitic gulls in order to meet the nutritional status of the chick, although an effect of adult body condition could not be excluded.

First Record of a Banded Sandwich Tern (Thalasseus sandvicensis) Moving from England to the United States

Abstract. A Sandwich Tern (Thalasseus sandvicensis sandvicensis) banded as a chick in 2002 at Coquet Island off the northeast coast of Great Britain was observed at two locations on Cape Cod, Massachusetts, USA, in August and September 2013. This is the first record of a banded Sandwich Tern from the United Kingdom being observed in the United States.

Bird mortality from the Deepwater Horizon oil spill. II. Carcass sampling and exposure probability in the coastal Gulf of Mexico

Two separate approaches, a carcass sampling model and an exposure probability model, provided estimates of bird mortalities of 600 000 and 800 000, respectively, from the 2010 Deepwater Horizon MC 252 oil spill in coastal waters of the Gulf of Mexico. Monte Carlo simula- tion of parameter uncertainty led to respective 95% uncertainty intervals of 320 000 to 1200 000 and 160 000 to 1900 000. Carcass sampling relied on expansion factors multiplied by counts of bird carcasses retrieved in shoreline surveys, whereas exposure probability estimated bird deaths as a product of estimated coastal bird density, average oil slick size, slick duration, and proportionate mortality due to oiling. The low proportion of small-sized carcasses recovered, compared with considerably higher proportions of small live birds in coastal Gulf habitats, indicate an especially low probability of recovery for small birds after oil spills at sea. Most mortality affected 4 species: laughing gull Leucophaeus atricilla (32% of the northern Gulf of Mexico population killed), royal tern Thalasseus maximus (15%), northern gannet Morus bassanus (8%) and brown pelican Pele- canus occidentalis (12%). Declines in laughing gulls were confirmed by ~60% reductions in National Audubon Society Christmas Bird Count data for 2010−2013 along the Gulf coast. Popu- lation-level effects in apex predators of this magnitude likely had effects on prey populations that warrant careful assessment.

Predation of Greater Crested Tern (Thalasseus bergii) Eggs by Juvenile Brown Boobies (Sula leucogaster) on Ashmore Reef

As young seabirds approach independence, a range of tactics are sometimes employed in an attempt to secure additional food items prior to departing the nest. Detailed here are previously unreported kleptoparasitic and predatory behaviors of juvenile Brown Boobies (Sula leucogastei) on Ashmore Reef in the Timor Sea. From 14–20 November 2013, the number of Greater Crested Terns (Thalasseus bergii) breeding adjacent to a Brown Booby colony was reduced from 128 adults attending the colony to 59 adults. During this time, two juvenile Brown Boobies were observed depredating the eggs of the Greater Crested Terns and ingesting prey regurgitated by Greater Crested Terns. The factors that lead to this unusual foraging behavior in juvenile Brown Boobies are not known; however, low body mass and hunger may play a role. Repeated years of predation of Greater Crested Tern eggs by Brown Boobies could lead to the abandonment of this colony.

Winners and losers – responses to recent environmental change by South African seabirds that compete with purse-seine fisheries for food

There were recent changes in the distributions of the main prey of four seabirds off South Africa, with sardine Sardinops sagax and anchovy Engraulis encrasicolus shifting from South Africa's north-west coast towards the south-east. This contributed to numbers of African Penguins Spheniscus demersus and Cape Cormorants Phalacrocorax capensis breeding in South Africa decreasing by more than 50%. By contrast, numbers of Cape Gannets Morus capensis and Swift (Crested) Terns Thalasseus bergii increased. The success of the gannet and the tern in the face of recent change is attributable to a rapid increase in South Africa's eastern colony of gannets, aided by high survival of adult birds and perhaps by immigration of first-time breeders from decreasing western colonies, and a probable high production of Swift Terns. The gannet has an extensive foraging range and the tern is nomadic between breeding localities, which gives these species greater flexibility than the other two to adapt to large changes in the distributions of their prey. Additionally, the gannet is able to supplement its diet with fishery discards. A lesser mobility of the African Penguin and the Cape Cormorant rendered them susceptible to a reduced local availability of prey and both species suffered high adult mortality in the last decade.

TernCam: an automated energy-efficient visual surveillance system

The Matsu Islands in Taiwan are an archipelago of islands surrounded by the sea. Some of the islands are chosen as the breeding places by many kinds of migratory birds. Among these sea birds, one of the critical endangered species is the Chinese Crested Tern Thalasseus bernsteini. In the past, its habitual ecological behaviour has been inspected by manual observation with trivial information. Thus, we developed a wireless real-time visual surveillance system to monitor the terns, so the in-situ situation could be captured immediately. It is expected that the system can unravel the mysterious ecological behaviour of the tern. Meanwhile, in order to be suitable for the circumstances of wild islands, the system is designed with a specific packet transmitting strategy capable of increasing image validity while decreasing power consumption. The experimental results show the system is feasible for ecological monitoring and able to effectively preserve the image completeness.

Long-term change in the population sizes and conservation status of South Africa's seabirds

Since the early 1980s, there have been large decreases in numbers breeding in South Africa of three seabirds that compete with fisheries for food: African Penguin Spheniscus demersus, Cape Cormorant Phalacrocorax capensis and Bank Cormorant P. neglectus. By contrast, two other species that compete with fisheries but which have a larger foraging range when breeding or are nomadic between breeding localities, Cape Gannet Morus capensis and the nominate race of Swift Tern Thalasseus bergii bergii, have increased. Five seabirds that do not compete with fisheries for prey have maintained stable populations or increased. The decreases in the three species have led to deterioration in the overall conservation status of South Africa's seabirds, of which 10 of 15 species (67%) are presently classified as Threatened or Near-threatened, including six of the seven species that are endemic to the Benguela ecosystem off western southern Africa.

Reproductive biology of Cabot's Terns on Cardos Island, Santa Catarina, Brazil

Cabot's Terns Thalasseus acuflavidus (Latham, 1737) are widely distributed along the Atlantic coast of South America from the Caribbean Islands (12º S) to the region of Porto Deseado, Argentina (46º S). Daily observations were conducted on the Cardos Island during 2003, 2005 and 2006 to determine timing and nesting success, and the reproductive biology of the Cabot's Terns nesting there. The first adults arrived at the colony from 22 April to 15 May during the three years recorded; a total of 144 nests were recorded in 2003, 174 in 2005 and 50 in 2006. Observed incubation time was 24.1 ± 0.35 days, and mean egg size was 5.15 ± 0.02 cm in length and 34.30 ± 0.25 g in weight. Hatching success was lowest in 2003 and highest in 2006, with natural causes (such as nest abandonment, flooding, inter and intra-specific fight) being the main cause of loss. The first eggs hatched in July in 2003, and in June in 2005 and 2006. Overall nesting success was lowest (4.00%) in 2006 and much higher (36.1% and 27.01%, respectively) in 2003 and 2005.

The breeding biology of Chinese Crested Terns in mixed species colonies in eastern China

SummaryThe Chinese Crested Tern Thalasseus bernsteini is a Critically Endangered species and very little is known about its breeding biology and behaviour. Only two small breeding colonies have been recorded on the eastern coast of China. Between 2004 and 2009, their breeding biology was studied in two mixed species colonies on the Jiushan and Wuzhishan archipelagos in Zhejiang province. Chinese Crested Terns started breeding in late May and departed in late August, and nests were generally found within large colonies of Greater Crested Terns T. bergii. The nesting grounds of the mixed colony included grass, rock and interlaced zones on small, uninhabited islets. A total of six Chinese Crested Tern nests were identified, four of which were monitored. In these, the average clutch size was one, with an incubation period of 22–28 days and a fledging period of 31–35 days. The chicks subsequently joined chicks of the Greater Crested Tern, forming the same crèche. Adult Chinese Crested Terns foraged within approximately 5 km of the breeding islets and fed their chicks mainly with small and/or young shoaling fishes. The breeding success of Chinese Crested Tern was 100% in both 2008 and 2009. In addition to mixed nesting, other traits of breeding biology, such as breeding site shifts and re-nesting, provide valuable information for surveying, monitoring and conservation of the Chinese Crested Tern.

Population structure in the South American tern Sterna hirundinacea in the South Atlantic: two populations with distinct breeding phenologies

The South American tern Sterna hirundinacea is a migratory species for which dispersal, site fidelity and migratory routes are largely unknown. Here, we used five microsatellite loci and 799 bp partial mitochondrial DNA sequences (Cytochrome b and ND2) to investigate the genetic structure of South American terns from the South Atlantic Ocean (Brazilian and Patagonian colonies). Brazilian and Patagonian colonies have two distinct breeding phenologies (austral winter and austral summer, respectively) and are under the influence of different oceanographic features (e.g. Brazil and Falklands/Malvinas ocean currents, respectively), that may promote genetic isolation between populations. Results show that the Atlantic populations are not completely panmictic, nevertheless, contrary to our expectations, low levels of genetic structure were detected between Brazilian and Patagonian colonies. Such low differentiation (despite temporal isolation of the colonies) could be explained by demographic history of these populations coupled with ongoing levels of gene flow. Interestingly, estimations of gene flow through Maximum likelihood and Bayesian approaches has indicated asymmetrical long term and contemporary gene flow from Brazilian to Patagonian colonies, approaching a source–sink metapopulation dynamic. Genetic analysis of other South American tern populations (especially those from the Pacific coast and Falklands–Malvinas Islands) and other seabird species showing similar geographical distribution (e.g. royal tern Thalasseus maximus), are fundamental in gaining a better understanding of the main processes involved in the diversification of seabirds in the southern hemisphere.