Common Terns Research Articles

A case study of the 2023 highly pathogenic avian influenza (HPAI) outbreak in tern (Sternidae) colonies on the east coast of the Republic of Ireland

ABSTRACT Capsule:HPAI H5N1 had a significant impact on breeding Common Terns Sterna hirundo, Arctic Terns Sterna paradisaea and Roseate Terns Sterna dougallii on the east coast of the Republic of Ireland (ROI) in 2023, with a lesser impact on Sandwich Terns Thalasseus sandvicensis and only two cases among Little Terns Sternula albifrons. Aims: To document the outbreak of HPAI H5N1 in the tern colonies on the east coast of ROI during the 2023 breeding season. Methods:Precautions were taken from the start of the breeding season, including personal protective equipment (PPE) and safe operating procedures. Regular meetings were held between BirdWatch Ireland and the National Parks and Wildlife Service (NPWS) to respond to the emerging situation. Once HPAI was confirmed in a colony, all ringing and nest visits were stopped. Carcass removal was carried out at all affected colonies and most carcasses were incinerated. Results: Common Terns suffered the highest mortality across all colonies in 2023, with smaller but notable numbers of dead Roseate Terns and Arctic Terns, but very few Sandwich Terns and only two Little Tern deaths were attributed to HPAI. Conclusion: Regular meetings between relevant organizations were invaluable in preparing for outbreaks and ensuring an adaptive approach as the situation changed over time and between colonies. There was no way of knowing if the actions taken were effective, as the pattern of virus spread between species and sites remains poorly understood. Future clarity over the role of various state agencies and other relevant bodies in responding to HPAI in wild birds, greater sharing of real-time information, and pre-arranged agreements to ensure rapid testing and disposal of carcasses, would be useful to ensure an effective response to future outbreaks.

Changes of nestling ringing dates in nine bird species over seven decades

Climate change co-occurs with an advancement of avian breeding season (indexed as laying dates or fledging dates) in the temperate zone, suggesting a causality between them. Here, we investigate whether the long-term shifts in nestling (chick) ringing dates also mirror this phenomenon. This index is biased by inherent shortcomings, such as the non-independence of dates (in nestmates, colony members), poor accuracy (long period suitable for ringing), and strange shape of distributions. These shortcomings can be reduced by applying the median of annual ringing dates as an index of breeding phenology. The advantage of this index is that data are available for long periods and large sample sizes. By accepting certain compromise between statistical discipline and fieldwork realities, we examined changes in the breeding phenology of 9 bird species from 1951 to 2020 in Hungary. We found that the annual median of ringing dates advanced significantly (by 9–14 days) in the Black-headed Gull, Common Kestrel, Barn Swallow, Great Tit, and Eurasian Blue Tit. Contrarily, no significant (all P > 0.16) changes occurred in the case of the Common Tern, Black-crowned Night-heron, Common Buzzard, and Long-eared Owl. We also found that the proportion of Great Tits’ second brood has been reduced in recent decades.

Mercury concentrations in blood and back feathers are repeatable, heritable and correlated in a long-lived seabird

Mercury pollution is increasing both in the environment and in various organisms, especially top-predators. If variation in individual mercury concentrations is underpinned by genetic among-individual differences in traits related to mercury uptake, storage or excretion, and results in variation in fitness, populations may have the potential to evolve in response to this development. Few studies, however, have been able to collect sufficient information to investigate the genetic basis of pollution levels. We ran Bayesian quantitative genetic analyses, combining pedigree information obtained from a marine top-predator, the common tern (Sterna hirundo), with total mercury concentrations (THg) measured in 1364 blood and 1560 back feather samples obtained from >600 individual birds across seven years. Blood and back feather THg concentrations differed in repeatability (19 vs. 64 %, respectively), but showed similar levels of heritability (c. 9 %) and evolvability (c. 2 %). Blood and back feather THg concentrations were positively correlated at the phenotypic, but not genetic, level. Although further work is needed to elucidate the uptake, storage or excretion pathways underlying these patterns, our study provides pioneering insights into the architecture of THg concentrations, and suggests that adaptation to environmental pollution may to some extent be possible.

The effect of localized disturbance on the acoustic behavior of the common tern (Sterna hirundo).

In this study, passive acoustic monitoring was used to assess the impact of investigator disturbance on the acoustic behavior of a colony of common terns. A graded antipredator response in the colony was hypothesized, which would result in an increase in acoustic energy with increased proximity to investigator disturbance. Human disturbance was found to result in a significant increase in acoustic energy within 20 meters of recorders, though not from farther distances. Our findings provide a framework for assessing the behavioral impact of disturbance on colonies and support the existence of a graded alarm call system in common terns.

River and sea: foraging range of freshwater and marine Common Terns

River and sea: foraging range of freshwater and marine Common Terns

Mercury bioaccumulation in three colonial seabird species in the Gulf of Maine

The methylated form of mercury, MeHg, is a neurotoxin that bioaccumulates and biomagnifies through aquatic food webs, reaching high concentrations in top trophic species. Many seabird species are wide-ranging and feed on forage fish, so they can be used as sentinel species to assess the level of mercury in pelagic or coastal food webs because they integrate the signal from large areas and from lower trophic levels. The Gulf of Maine provides habitat for many seabirds, including endangered roseate terns (Sterna dougalii), common terns (Sterna hirundo), and the southernmost breeding population of black guillemots (Cepphus grylle). Hg levels were assessed in down of newly hatched chicks of three seabird species to determine pre-hatching Hg exposure. Stable isotopes (δ15N, δ13C) in down and chick contour feathers grown after hatching were used as indicators of adult female diet in the period before laying the egg (down) and pre-fledging chick diet (contour feathers). Black guillemot down THg concentrations were 10.07 ± 2.88 μg/g (mean ± 1SD), 5.5× higher than common tern down (1.82 ± 0.436 μg /g), and 7.4× higher than roseate tern down (1.37 ± 0.518 μg/g). Black guillemots also had higher down feather δ15N values (15.1 ± 0.52 ‰) compared to common (13.0 ± 0.72 ‰) or roseate terns (12.8 ± 0.25 ‰), and in black guillemot down feathers, higher Hg concentrations were correlated with δ15N, an indicator of trophic level. Repeated testing of the same tissue types across multiple years is needed to monitor THg exposure for seabirds in the Gulf of Maine; additionally, monitoring species composition and Hg presence in prey species of the black guillemot population would help to determine the source of high THg concentrations in this species.

Population size and nesting peculiarities of the black-headed gull Chroicocephalus ridibundus (Linnaeus, 1766) on the territory of water treatment facilities

Background. Today, the black-headed gull inhabits man-made areas of wastewater treatment facilities (WTF) to comensate for the the reduction of natural aquatic and wetland habitats. Over the last decade, a nearly tenfold increase in its population has been recorded, despite a low reproduction rate. This fact indicates the lack of stability in the bird population, necessitating thorough research. Materials and Methods. The analysis of the population size and biological charac­teristics of black-headed gulls involved censuses and observations at the WTF of the city of Kharkiv using conventional methods during the spring-summer periods of 2020–2021 and 2023. Results. The population of the black-headed gull reached its peak in the third decade of May 2020 (2637 individuals) and 2023 (2124 individuals), as well as in the second decade of May 2021 (3949 individuals). The maximum nesting density was observed on sludge sites (SS) of wastewater treatment facilities that are most similar to natural habitats, where dried mud alternates with water patches and vegetation at the bottom and around the perimeter (Type V): 236.7±26.7 pairs/ha in 2020 and 242.9±28.5 pairs/ha in 2021. The majority of nests were found in the first decade of May 2021 and the third decade of May 2020. The black-headed gull forms mixed-species, occasionally monospecific subcolonies. Nesting in association with it were: Sterna hirundo, Anas platyrhynchos, Spatula clypeata, Vanellus vanellus, Charadrius dubius, Himantopus himantopus, Fulica atra, Gallinula chloropus, and Aythya ferina. The size of the complete black-headed gull clutch was 3.1±0.4 eggs (n = 190). The egg dimensions were 50.9±2.1 ´ 36.2±1.1, with a mass of 34.6±2.8 g. Regarding shell coloration, five types of background colors were identified. Mass egg laying occurred from the third decade of April to the first decade of May, constituting 40.3 % (n = 993) in 2020 and 62.3 % (n = 1757) in 2021. The egg-laying period extended from April to July, with the latest non-incubated clutches recorded in the first decade of July (3.07.2020). The first chicks were found in nests in the first decade of May, while mass hatching occurred in the second half of May. The latest registration dates of the birds on nesting territories were in the second decade of July for 2020 and 2023, and the first decade of August for 2022. The nesting season duration varied from 125 to 140 days in different years. Autumn migration commenced with summer relocations and concluded from late October to early November. The reproductive success – the percentage of nestlings that fledged and successfully achieved flight – constituted 29.2 % (n = 2404 of laid eggs) in 2020, and 15.5 % (n = 6138) in 2021. The majority of offspring perished due to changes in water levels (prolonged rainfall or industrial wastewater discharge), predation, disturbance factors, etc. Conclusion. The colonial nesting of the black-headed gull creates favorable conditions for the habitation and reproduction of various bird species, including rare ones, which is essential for their conservation.

Diversity and Abundance of Wetland Birds in Udayamarthandapuram Bird Sanctuary, Tiruvarur District, Tamil Nadu, India

Wetland birds are integral components of wetland ecosystems, providing ecological, economic, cultural, and regulatory benefits. The study conducted from 2021 to 2024 in the Udayamarthandapuram Bird Sanctuary of Tiruvarur district aimed to assess year-wise species diversity, richness, relative diversity, evenness, density, and relative abundance of wetland birds employing the total count method to estimate the population of wetland birds. A total of 104 bird species belonging 18 orders and 49 families were recorded. During this study, 17 species were migrant, while the remaining 87 birds were resident. Three bird species were classified as Near Threatened, including the Spot-billed Pelican (Pelecanus philippensis), Black-headed Ibis (Threskiornis melanosephalus), and Oriental Darter (Anhinga melanogaster). Additionally, two bird species were classified as Vulnerable, namely the Greater Spotted Eagle (Clanga clanga) and River Tern (Sterna hirundo), while 99 bird species were classified as Least Concern. Regarding species diversity in the Udayamarthandapuram Bird Sanctuary during different years, the highest species diversity was recorded in 2021 (2.75), while the lowest species diversity was observed in 2024 (1.64). In terms of species richness, the maximum richness was observed in 2023 (68), whereas the minimum species richness was recorded in 2022 (29).

Status, Diversity and Species Composition of Wetland Birds on Vaduvoor Bird Sanctuary, Tiruvarur District, Tamil Nadu, India

Birds serve as the best indicators of wetland function and as measures of success in wetland management, restoration, and creation. This study was conducted from 2022 to 2024 in the Vaduvoor Bird Sanctuary of Tiruvarur district, employing the total count method to estimate the population of wetland birds. Year-wise species diversity, richness, relative diversity, evenness, density, and relative abundance were calculated. A total of 147 bird species belonging to 48 families and 18 orders were recorded. The maximum diversity and evenness were observed in 2024 (3.05 and 0.37), while the minimum values were recorded in 2023 (2.11 and 0.21). The total density was highest in 2023 (162.68/ha) and lowest in 2024 (27.82/ha), and species richness peaked in 2022 (117) and was lowest in 2024 (84). This sanctuary complex supports three IUCN Red-listed, four Near Threatened species: Curlew Sandpiper (Calidris ferruginea), Spot-billed Pelican (Pelecanus philippensis), Black-headed Ibis (Threskiornis melanosephalus), and Oriental Darter (Anhinga melanogaster), two vulnerable species: Yellow-throated Bulbul (Pycnonotus xantholaemus) and River Tern (Sterna hirundo), and one Endangered species – Lesser Sand Plover (Charadrius mongolus). This paper provides an overview of the current status and the IUCN status of wetland birds within the study area.

Long-term dataset for contaminants in fish, mussels, and bird eggs from the Baltic Sea

Widespread persistent contaminants are a global environmental problem. In the Baltic Sea, wildlife contamination was first noticed in the 1960s, prompting the Swedish Environmental Protection Agency to establish a comprehensive Swedish National Monitoring Programme for Contaminants in Marine Biota (MCoM) in 1978 run by the Swedish Museum of Natural History. Eight species have been analysed, four fish species (Atlantic herring, Atlantic cod, European perch, viviparous eelpout), one bivalve species (blue mussel), and egg from three bird species (common guillemot, common tern, Eurasian oystercatcher). Here, we present a dataset containing MCoM data from its start until 2021. It includes 36 sets of time-series, each analysed for more than 100 contaminants. The longest time-series is for common guillemot and starts in 1968. We describe the structure of MCoM including historic changes to the number of stations, sample treatment, analytical methods, instruments, and laboratories. The MCoM data is available at the Bolin Centre repository and on GitHub through our R package mcomDb. The latter will be updated yearly with new MCoM records.

Sex- and age-specific mercury accumulation in a long-lived seabird

Mercury levels in the environment are increasing, such that they are also expected to accumulate in top-predators, but individual-based longitudinal studies required to investigate this are rare. Between 2017 and 2023, we therefore collected 1314 blood samples from 588 individual common terns (Sterna hirundo) to examine how total blood mercury concentration changed with age, and whether this differed between the sexes. Blood mercury concentrations were highly variable, but all exceeded toxicity thresholds above which adverse health effects were previously observed. A global model showed blood mercury to be higher in older birds of both sexes. Subsequent models partitioning the age effect into within- and among-individual components revealed a linear within-individual accumulation with age in females, and a decelerating within-individual accumulation with age in males. Time spent at the (particularly contaminated) breeding grounds prior to sampling, as well as egg laying in females, were also found to affect mercury concentrations. As such, our study provides evidence that male and female common terns differentially accumulate mercury in their blood as they grow older and calls for further studies of the underlying mechanisms as well as its consequences for fitness components, such as reproductive performance and survival.

Hematology and Serum Biochemistry of Coastal Seabirds Rehabilitated on the Southeastern and Southern Coast of Brazil.

Complete blood counts (n=566) and serum biochemistry (n=426) were assessed in seven coastal seabirds species that underwent rehabilitation along the southeastern and southern coast of Brazil from Saquarema, Rio de Janeiro State (22°56'16.44″S, 42°18'24.16″W) to Laguna, Santa Catarina State (28°29'43″S, 48°45'39.2″W), from August 2016 to August 2020. Blood samples were collected from four species of Charadriiformes, including Kelp Gull (Larus dominicanus, n=136), South American Tern (Sterna hirundinacea, n=25), Cabot's Tern (Thalasseus acuflavidus, n=17), and Common Tern (Sterna hirundo, n=14) as well as three species of Suliformes, the Brown Booby (Sula leucogaster, n=212), Magnificent Frigatebird (Fregata magnificens, n=104), and Neotropic Cormorant (Nannopterum brasilianum, n=58). The individuals were sampled as part of the protocol required before their release into the wild when considered healthy. This work aimed to establish the normal hematologic and biochemical reference values of those seabird species and, when possible, to analyze variations among age class and sex and to compare those with the available data in the literature. In addition, we provide the first baseline data for the South American Tern, Cabot's Tern, and Neotropic Cormorant. Baseline hematologic data are crucial for assessing health status of individuals and to support management and conservation actions, including release of seabirds into the wild.

Comparison of waterbird communities in a Mediterranean salina – saltmarsh complex

Coastal wetlands provide habitat for large numbers and many species of waterbirds. Man-made salinas are a particu-lar habitat type often found in such wetlands. This study is an initiative to understand the differences in bird communities between a salina (including evaporation ponds and prebasin) and a saltmarsh. Bird counts and nest surveys took place in the wetlands of Angelochori, Thessaloniki, Greece, in 1991, when the salina was inactive, and in 1997, 2000-01 when it was active. Counts in evaporation ponds were richer in species, abundance and nests compared to the prebasin and the saltmarsh. These three wetland types supported different bird communities. Similarities among bird communities depended on the inundation of the salina with seawater. Evaporation ponds in their inactive period presented low similarity with the communities of the prebasin and the saltmarsh ; in the active period this was observed only for the saltmarsh. Species showing clear selection for the evaporation ponds were Charadrius alexandrinus, Calidris alpina, Calidris minuta, Recurvirostra avosetta, Sterna hirundo, Sternula albifrons, Sterna sandvicensis and Haematopus ostralegus; the prebasin was preferred by Phoenicopterus roseus and Anas platyrhynchos, and the saltmarsh by Anas querquedula, Anas clypeata, Plegadis falcinellus, Tringa totanus, Tringa glareola, Tringa stagnatilis and Himantopus himantopus.

Mercury stable isotopes in seabirds in the Ebro Delta (NE Iberian Peninsula): Inter-specific and temporal differences

Mercury (Hg) is a global pollutant, which particularly affects aquatic ecosystems, both marine and freshwater. Top-predators depending on these environments, such as seabirds, are regarded as suitable bioindicators of Hg pollution. In the Ebro Delta (NE Iberian Peninsula), legacy Hg pollution from a chlor-alkali industry operating in Flix and located ca. 100 km upstream of the Ebro River mouth has been impacting the delta environment and the neighboring coastal area. Furthermore, levels of Hg in the biota of the Mediterranean Sea are known to be high compared to other marine areas. In this work we used a Hg stable isotopes approach in feathers to understand the processes leading to different Hg concentrations in three Laridae species breeding in sympatry in the area (Audouin's gull Ichthyaetus audouinii, black-headed gull Chroicocephalus ridibundus, common tern Sterna hirundo). These species have distinct trophic ecologies, exhibiting a differential use of marine resources and freshwater resources (i.e., rice paddies prey). Moreover, for Audouin's gull, in which in the Ebro Delta colony temporal differences in Hg levels were documented previously, we used Hg stable isotopes to understand the impact of anthropogenic activities on Hg levels in the colony over time. Hg stable isotopes differentiated the three Laridae species according to their trophic ecologies. Furthermore, for Audouin's gull we observed temporal variations in Hg isotopic signatures possibly owing to anthropogenic-derived pollution in the Ebro Delta. To the best of our knowledge this is the first time Hg stable isotopes have been reported in seabirds from the NW Mediterranean.

Using soundscape to monitor population size, demographics, and antipredator behavior in a dense aggregation of colonial seabirds

Migratory seabirds are vulnerable to decline due to climate change and anthropogenic disturbances. Common terns (Sterna hirundo) are highly vocal colonial seabirds that serve as bioindicators of their foraging grounds throughout their migratory range. Historically, monitoring colonial seabirds is invasive and time-consuming, and traditional acoustic approaches are complicated by high amounts of call overlap. Monitoring the behavioral ramifications of disturbance, as well as overall colony size and health, is crucial to implementing effective management decisions. However, methods are needed to do so efficiently and with minimal disturbance. In this study, we demonstrate that population size, demographics, and behavior can be assessed acoustically through changes in acoustic energy across varying temporal scales. To do this, we compared acoustic energy to in-person observations of nest density, chick-hatching, and investigator disturbance. We found that trends in acoustic energy align with observations of nest density, and the distribution of acoustic energy across frequency bands is indicative of colony demographics. Furthermore, we found a significant relationship between acoustic energy and investigator disturbance within 20 meters of an acoustic recorder. Overall, our findings suggest that colony-wide trends in population size, demographics, and behavior can be monitored via acoustic energy without the time-consuming analysis of individual calls.

Movement patterns of foraging common terns (Sterna hirundo) breeding in an urban environment in coastal Virginia.

Nesting colonial seabirds are prime examples of central-place foragers, animals that must return to a central location (e.g., a breeding colony) after each bout of foraging. They must balance the costs and benefits of foraging with the need to return to their colonies frequently to form pair bonds during courtship, incubate, provision mates and offspring, and protect and rear young. For some populations, the loss and degradation of suitable breeding habitat due to human activities have necessitated the construction of new breeding sites and/or the restoration of previously occupied sites. South Island, which is part of the Hampton Roads Bridge-Tunnel (HRBT) complex in the Commonwealth of Virginia, U.S.A., is a human-created island that supported Virginia's largest mixed species seabird colony until 2020, when the expansion of the HRBT began and when all nesting seabirds were permanently excluded from the site. We studied the movement patterns of foraging common terns (Sterna hirundo) to determine how travel to and around foraging sites related to their colony location and to inform the siting and construction of a new breeding island. We tracked 18 individual common terns from 07 June to 29 June 2018, and we used a hidden Markov model to assign behavioral states and investigate common tern movements around the HRBT. Common terns spent more than half their time in the colony (58%), followed by time devoted to foraging (22%), and the remainder of their time was spent on outbound (15%) and inbound (5%) transit. Terns traveled as far as 98km from the colony, but on average foraged relatively close to South Island (13.6 ± 0.3km, mean ± 1 SD). Individuals tended to forage in the same locations, but there was variation among individuals. Flying to foraging sites uses energy during the already energetically costly breeding season, thus managers should prioritize placing a new colony site in a location that minimizes the distance traveled to the foraging locations frequented by the South Island birds while accounting for other life-history characteristics. These findings could help in the design and construction of new breeding sites or the restoration of current sites for other, related species, particularly for which these data do not exist.

Usurpation and Brooding of Least Tern (Sternula antillarum) Chicks by Common Terns (Sterna hirundo)

While nest usurpation and subsequent incubation of eggs and even brooding of chicks from other species has been reported for Common Terns (Sterna hirundo), such behavior is considered rare. We report an observation of a Common Tern pair usurping the Least Tern (Sternula antillarum) nest and brooding the Least Tern chicks. While the Least Tern pair attempted to provide care for the chicks, the Common Terns displayed aggressive behavior and defended the nest. Though both species attempted to feed the chicks, no feeding events were observed due to harassment from the other species. Neither pair was observed nesting prior to or following this event, and all chicks are believed to have been lost to predation. We discuss the possible scenarios leading to the observed usurpation event, the possibility that usurpations are more common than previously believed, and the need for different monitoring methods to elucidate the causes of usurpations.

Waterbird community changes in the Wilderness Lakes, South Africa (Part 3 of 3): Diving piscivores and scavengers

Estuarine waterbodies typically support diverse and abundant waterbird communities. However, global environmental degradation as a result of anthropogenic activities is leading to species level changes in biodiversity, with top predators such as piscivorous waterbirds being particularly vulnerable to ecosystem changes. The study aimed to document long-term spatial and temporal patterns of abundance of piscivorous and scavenging waterbirds in the Wilderness Lakes Complex (WLC) in the Garden Route National Park, South Africa, and where possible identify potential causes for observed trends. The abundance of waterbirds on these wetlands was determined biannually from 1992 to 2019, with counts conducted from a boat following a standardised route. Historical waterbird abundance data from the 1980s were also used to describe long-term abundance changes. Eight of the species exhibited seasonal variability in abundance with most, excluding Common Tern Sterna hirundo, being more abundant in winter. Substantial changes occurred in the abundance of several species over the four-decade study period, notably increases in Cape Cormorant Phalacrocorax capensis and Great Crested Grebe Podiceps cristatus, and decreases in Common Tern and Black-necked Grebe Podiceps nigricollis. Long-term abundance trends indicate a combination of declining, increasing, and stable populations. Although some species have undergone contrasting abundance changes on different waterbodies in the WLC the dominant pattern was a similar direction of change on most or all waterbodies and in different seasons. Local reasons for changes probably include loss of sandbanks, changing prey availability, and the absence of recreational disturbance on some waterbodies.Conservation implications: Drivers of changes in the abundances of piscivores are likely to be multifaceted, functioning on multiple spatial and temporal scales, and affecting different species in different ways. Recommended local corrective actions include managing emergent macrophyte encroachment on sandbanks, reducing recreational disturbance, managing processes affecting indigenous fish stocks, and protecting nesting sites.

Sex-specific foraging behaviour in a long-lived seabird

Sex-specific foraging behaviour may lead to differences between the sexes in both resource acquisition and exposure to threats and thereby contribute to sex-specific reproductive roles or mortality. As such, it is important to identify in which species sex-specific foraging behaviour occurs. We deployed GPS devices to incubating common terns (Sterna hirundo) from a German breeding population to study how sex and spatial or temporal extrinsic factors influence the daily activity budget, foraging distribution, and trip characteristics of this slightly sexually size dimorphic seabird. Birds of both sexes only foraged during the day, showing peaks of activity after sunrise and before sunset, perhaps in response to temporal variation in prey availability and/or as a strategy to overcome or prepare for nocturnal fasting. Furthermore, foraging was more frequent around low tide and at the beginning of the flood tide and mainly occurred in shallow (< 5 m depth) and coastal waters (< 2 km from coastline) up to 20 km from the colony. Females rested less, foraged closer to the colony in more coastal waters, and showed a lower maximum flight speed than males. Males foraged more outside protected areas than females and showed higher variability in their foraging distribution throughout the tide cycle. As such, our study provides evidence for sex-specific aspects of foraging behaviour in common terns and underlines the importance of considering sex-specific foraging distributions when assessing the impact of at-sea threats on seabirds, knowledge of which should be incorporated when developing conservation management strategies.

Colonial Nesting Sea Birds (Charadriiformes: Laridae) of Peter the Great Bay, the Sea of Japan

The paper presents the recent data on the distribution and breeding abundance and distribution of the Mongolian Gull, Slaty-backed Gull, Black-tailed Gull and the Common Tern nesting within Peter the Great Bay of the Sea of Japan. Over the past 30 years, all species of gulls increased their abundance, while the Common Tern has almost ceased to nest on the islands of the bay.