Black Tern Research Articles

Distribution and abundance of marsh-nesting colonial waterbirds in Prairie Canada

Waterbird species face numerous threats and many are declining globally, but knowledge of distribution, abundance, and trend remains poor for many species. Five species of marsh-nesting colonial waterbirds are poorly monitored in Canada, and especially so in the core of their range in the Canadian Prairie Provinces (Alberta, Saskatchewan, and Manitoba). We summarized published and unpublished data on abundance and distribution of breeding colonies of Western Grebe (Aechmophorus occidentalis), Franklin's Gull (Leucophaeus pipixcan), Black Tern (Chlidonias niger), Forster's Tern (Sterna forsteri), and Black-crowned Night-Heron (Nycticorax nycticorax) in Alberta, Saskatchewan, and Manitoba. We also examined the degree of overlap in nesting phenology (egg dates) and summarized survey methods that have been used to monitor the species during the breeding season—information that may be useful for the development of a multispecies monitoring program. For all species, the largest number of records of breeding colonies occurred in Alberta, with records declining eastward through Saskatchewan and Manitoba. We identified a number of breeding colonies occurring outside of currently defined species ranges, especially for the poorly studied Forster's Tern. Of 137 waterbodies hosting a colony of at least one species over the past 10 yr, 57 (41.6%) hosted colonies of at least 2 species, and 3 (2.2%) hosted colonies of all 5 species. Species tended to be reasonably synchronous in their breeding phenology, but Franklin's Gulls and Black-crowned Night-Herons tended to initiate nesting slightly earlier than the other species. We conclude that a multispecies survey timed in late May or early June to count nests and/or incubating adults, using either ground-based or aerial surveys, would likely be the most appropriate for monitoring all species jointly in the Prairie Provinces. The approach we take to compiling data from multiple sources on species occurrence and breeding phenology may be applicable to others wishing to examine the feasibility of a multispecies monitoring plan.

Clustering and ensembling approaches to support surrogate‐based species management

AbstractAimSurrogate species can provide an efficient mechanism for biodiversity conservation if they encompass the needs or indicate the status of a broader set of species. When species that are the focus of ongoing management efforts act as effective surrogates for other species, these incidental surrogacy benefits lead to additional efficiency. Assessing surrogate relationships often relies on grouping species by distributional patterns or by species traits, but there are few approaches for integrating outputs from multiple methods into summaries of surrogate relationships that can inform decision‐making.LocationPrairie Pothole Region of the United States.MethodsWe evaluated how well five upland‐nesting waterfowl species that are a focus of management may act as surrogates for other wetland‐dependent birds. We grouped species by their patterns of relative abundance at multiple scales and by different sets of traits, and evaluated whether empirical validation could effectively select among the resulting species groupings. We used an ensemble approach to integrate the different estimated relationships among species and visualized the ensemble as a network diagram.ResultsEstimated relationships among species were sensitive to methodological decisions, with qualitatively different relationships arising from different approaches. An ensemble provided an effective tool for integrating across different estimates and highlighted the Sora (Porzana carolina), American Avocet (Recurvirostra Americana) and Black Tern (Chlidonias niger) as the non‐waterfowl species expected to show the strongest incidental surrogacy relationships with the waterfowl that are the focus of ongoing management.Main conclusionsAn ensemble approach integrated multiple estimates of surrogate relationship strength among species and allowed for intuitive visualizations within a network. By accounting for methodological uncertainty while providing a simple continuous metric of surrogacy, our approach is amenable to both further validation and integration into decision‐making.

Drivers of Intra-Seasonal Variation in Black Tern (Chlidonias niger) Nest Survival

Intra-seasonal changes in depredation influence nest survival, but this may be mediated by the foraging behavior of predators or seasonal variability in habitat features. Intra-seasonal differences in factors influencing daily nest survival rates of Black Terns (Chlidonias niger) were studied in southern Ontario, Canada, during May-August 2015 and 2016. Survival of early and late-nesting individuals in relation to nest-specific temporal and spatial characteristics was investigated, including nest habitat change over the nesting cycle. The daily nest survival rate for early nesters (n = 112) declined with increasing nest age (β = -14.97; P = < 0.001), and rose with increased proportion of vegetation (β = 0.01; P = 0.02) and increased conspecific nest spacing (β = 0.01; P = 0.04). Daily nest survival rate for late nesters (n = 80) was influenced by increasing nest age (β = -12.99; P = < 0.001), with a decline during the nestling stage, and no habitat or spatial correlates. A propensity toward smaller clutch sizes with diminished survival in the late season (β = 0.67; P = 0.01) further highlights intra-seasonal differences in factors that affect survival. Predator foraging behavior may influence intra-seasonal survival patterns more than seasonal variability in habitat features.

Genetic characterization of HPAI H5N8 viruses identified in wild and domestic birds in Uganda, 2017

Purpose: In early January 2017, outbreaks of H5N8 highly pathogenic avian influenza (HPAI) were reported for the first time on the shores and Islands of Lake Victoria in Central Uganda. An unusual high mortality was detected among white-winged terns in the districts of Masaka, Wakiso and Kalangala (Ssese Islands). A spill over from wild to domestic birds was identified in chickens and ducks in all the three districts. The purpose of our study was to genetically characterize the Avian Influenza viruses identified in Uganda during the H5N8 epidemic in the African continent. Methods & Materials: By using an Illumina MiSeq platform, we generated the complete genome of three viruses isolated from a white winged black tern, a domestic duck and a chicken. We then performed a phylogenetic analysis of the eight gene segments of these viruses together with the available sequences of the H5N8 virus A/grey-headed_gull/Uganda/MUWRP-538/2017, present in the public database. Results: The phylogenetic analyses of the eight gene segments revealed that the Ugandan H5N8 viruses belonged to genetic clade 2.3.4.4, group B and clustered with the viruses collected in May 2017 in the Democratic Republic of the Congo as well as with a virus from Cameroon (A/duck/Cameroon/17RS1661-3/2017). Differently, they showed a low similarity with the H5N8 viruses detected in 2017 in South Africa, Egypt and in some of the viruses isolated in Cameroon. Conclusion: The occurrence of H5N8 outbreaks in wild birds during the rainy season, when Uganda provides a recovery for many migratory species of birds, suggests that infected migratory wild birds might have played a crucial role in the introduction of HPAI H5N8 into this region. The low level of similarity detected among the Ugandan, South African and Egyptian strains suggests that the outbreaks in these countries were caused by separate virus introductions. However, viruses genetically related to the ones identified in South and North Africa could have been circulating in un-sampled locations. More detailed data need to be collected and combined to reconstruct the dynamics of the disease in the continent and to develop tailored control measures.

Great Crested Grebe (Podiceps cristatus) synchronies egg laying with protective species

Great crested grebes (Podiceps cristatus) are opportunistic breeders nesting in colonies or solitarily in different biotopes with varying nesting dates in different circumstances. On the northern coast of the Neva Bay in the eastern part of the Gulf of Finland, great crested grebes breed solitarily, in colonies situated in reed beds and in a colony on the open water in direct vicinity of a colony of black-headed gulls (Larus ridibundus) and black terns (Chlidonias niger). In the vicinity of the larid colony, grebes profit from the protecting behaviour of gulls and terns in a similar way as they do in their mixed colonies with larids. Despite the fact that small larids have a shorter incubation period than great crested grebes, the latter synchronize their beginning of incubation with the gulls and terns. The incubation of all three species in two adjoining open-water colonies started on the same dates. The incubation of grebes nesting in the reed beds began significantly later. The average clutch sizes did not differ significantly between the colonies situated on the open water near larids and those in the reeds. The average lowest distances between the nests of great crested grebes in the open water colony were larger than in the reed bed colonies. The ability to synchronize the beginning of incubation with a small protecting species helps great crested grebes to occupy otherwise unsafe habitats.

Semi-Supervised Fine-Grained Image Categorization Using Transfer Learning With Hierarchical Multi-Scale Adversarial Networks

Fine-grained image categorization is still a challenging computer vision problem in recent years. Most of existing methods highly rely on massive labeled data which are scarce in many real world applications. It should also be noticed that progressive learning demands of existing data is very common today. That is, we may pay attention to more fine-grained information (like arctic tern, black tern, buttercup or tulip) in an existing data set with labels like “bird” and “flower”. It is reasonable to believe that the existing labels and model with transferable knowledge would be helpful to another related but different, fine-grained recognition task. In this context, an improved transfer deep learning approach with hierarchical multi-adversarial networks is proposed in this paper. With this approach, cross domain features are extracted by advanced deep encoders coarsely. After that, we annotate a small amount of images in the target domain, thereby creating the “active labels” which can provide instructions for adversarial learning. Then, the GAN-based hierarchical model is utilized to select cross domain categories and enhance related features so as to facilitate an effective transfer. In order to exploit useful local features, a novel adaptive attention mechanism, Region Adversarial Network (RAN) which can select attention regions during adversarial learning and generate valuable fine-grained features, is introduced in the article. We call the proposed hierarchical framework “Attentional Multi-Adversarial Networks (AMAN)” . Experimental results show that AMAN is able to augment cross domain features well-directly and build an effective classifier for fine-grained categorization in the target domain with fewer training samples and higher accuracies.

Differences in nest site characteristics and hatching success in White-winged Tern (Chlidonias leucopterus) and Black Tern (Chlidonias niger)

Nests should be built on sites that provide optimal conditions for reproduction, so nest site characteristics are assumed to have an adaptive value. In this paper, we compared the hatching success of two species of terns: Black Tern (Chlidonias niger) (a non-expanding species) and White-winged Tern (Chlidonias leucopterus) (an expanding species, new to the region since 1997) with respect to microhabitat nest characteristics on oxbow lakes in eastern Poland. The hatching success of White-winged Tern was lower than that of Black Tern (41.7 vs. 66.7%). Comparison of habitat parameters at the nesting sites between the two tern species showed a significantly greater depth of water and distance from helophytes in White-winged Tern. Successfully hatched White-winged Tern clutches were situated much closer to the helophytes and were initiated on average up to 8 days earlier than clutches that failed to hatch. In Black Tern, hatching success was not influenced by environmental factors describing nest location. In eastern Poland, oxbow lakes are probably a suboptimal habitat and constitute an “ecological trap” for White-winged Tern; because of these suboptimal habitats, the expansion of this species may be quite slow in predominantly dry years in eastern Poland.

Breeding birds and anurans of dynamic coastal wetlands in Green Bay, Lake Michigan

Abstract Breeding birds and anurans (frogs and toads) in coastal wetlands of Green Bay, Lake Michigan vary dynamically with changing water levels, habitat type, and geography. We describe species assemblages over a seven-year period (2011–2017) beginning with historic low water levels followed by an increase in average lake level of 0.85 m. In general, species richness and abundance of marsh-obligate species responded positively to increasing water levels, although several species of shallow wetlands (sandhill crane, sedge wren, swamp sparrow, and American toad) showed the opposite trend. Anuran assemblages were more diverse in the middle and upper bay, coinciding with a well-established nutrient gradient from the hypereutrophic lower bay to more oligotrophic waters of the upper bay. Three marsh-obligate bird species (black tern, sandhill crane, and sedge wren) were significantly more abundant in the middle or upper bay while sora, American coot, and common gallinule were more abundant in the eutrophic lower bay. Our findings have several important implications for conservation. Inland wetlands near the coast (including diked wetlands) might play a key ecological role by providing refugia for some species during low water years. However, the importance of shallow coastal wetlands and nearshore gradients of wetland habitat might be overlooked during low water years; when high water returns, these areas can become extremely productive and species-rich.

Notable recent records of terns, gulls and skuas in southern Mozambique including the first country records of Black Tern Chlidonias niger

Interesting sightings in southern Mozambique of 13 species of terns, gulls and skuas are reported, the result of regular observations between October 2010 and September 2017 while I was based in the capital, Maputo. These include the first two records of Black Tern Chlidonias niger, the first fully documented record of Lesser Noddy Anous tenuirostris and the first observations of live Arctic Terns Sterna paradisaea for Mozambique, as well as status updates for Kelp Gull Larusdominicanus, Lesser Black-backed Gull L. fuscus, Sabine's Gull Xema sabini, Gullbilled Tern Gelochelidon nilotica, Swift Tern Thalasseus bergii, Sooty Tern Onychoprionfuscatus, Common Tern Sterna hirundo, Black-naped Tern S. sumatrana, Roseate Tern S. dougallii and Subantarctic Skua Stercorarius antarcticus in southern Mozambique.

Notable recent records of terns, gulls and skuas in southern Mozambique including the first country records of Black TernChlidonias niger

Notable recent records of terns, gulls and skuas in southern Mozambique including the first country records of Black Tern<i>Chlidonias niger</i>

Multispecies benefits of wetland conservation for marsh birds, frogs, and species at risk

Wetlands conserved using water level manipulation, cattle exclusion, naturalization of uplands, and other techniques under the North American Waterfowl Management Plan (“conservation project wetlands”) are important for ducks, geese, and swans (“waterfowl”). However, the assumption that conservation actions for waterfowl also benefit other wildlife is rarely quantified. We modeled detection and occupancy of species at sites within 42 conservation project wetlands compared to sites within 52 similar nearby unmanaged wetlands throughout southern Ontario, Canada, and small portions of the adjacent U.S., using citizen science data collected by Bird Studies Canada's Great Lakes Marsh Monitoring Program, including 2 waterfowl and 13 non-waterfowl marsh-breeding bird species (n = 413 sites) and 7 marsh-breeding frog species (n = 191 sites). Occupancy was significantly greater at conservation project sites compared to unmanaged sites in 7 of 15 (47%) bird species and 3 of 7 (43%) frog species, with occupancy being higher by a difference of 0.12–0.38 across species. Notably, occupancy of priority conservation concern or at-risk Black Tern (Chlidonias niger), Common Gallinule (Gallinula galeata), Least Bittern (Ixobrychus exilis), Sora (Porzana carolina), and Western Chorus Frog (Pseudacris triseriata) was significantly higher at conservation project sites compared to unmanaged sites. The results demonstrate the utility of citizen science to inform wetland conservation, and suggest that actions under the North American Waterfowl Management Plan are effective for conserving non-waterfowl species.

Male and female Black terns choose different prey types for chick provisioning

Male and female Black terns choose different prey types for chick provisioning

Macroinvertebrate Occurrence in Chlidonias niger (Charadriiformes: Laridae) Nests in East-Central Poland

Macroinvertebrate Occurrence in <i>Chlidonias niger</i> (Charadriiformes: Laridae) Nests in East-Central Poland

Black tern (Chlidonias niger) breeding site abandonment in U.S. Great Lakes coastal wetlands is predicted by historical abundance and patterns of emergent vegetation

Breeding colonies of black terns (Chlidonias niger) have become increasingly rare in U.S. Great Lakes coastal wetlands since the mid-twentieth century, with an almost 90% decline in the number of active colony sites since 1991. Although the specific causes of this wetland species’ decline are unknown, habitat loss and degradation are thought to be a major barrier to conservation. Using data from the Great Lakes Colonial Waterbird Survey, we took a unique regional and historical approach to investigate the relationship between black tern colony site abandonment and a suite of local and landscape-scale habitat features in U.S. Great Lakes coastal wetlands. We employed logistic regression models and a combination of stepwise selection procedures to identify the best predictive model for black tern colony abandonment. According to the selected model, breeding colonies with fewer nests were more likely to be abandoned over the following decadal observation period than breeding colonies with more nests. Colony sites were also more likely to be abandoned when vegetation within the wetland shifted towards larger, denser clusters. We performed a simulation study that showed that failing to account for association between observations from the same site affected model selection results, but that cross-validation error for the selected model remained low unless site effects were very strong. Results of this study suggest that focus on protection of sites harboring large numbers of black terns and vegetation management will help limit further colony abandonments.

Synapsis and recombination of autosomes and sex chromosomes in two terns (Sternidae, Charadriiformes, Aves)

The frequency of recombination and the patterns of crossover site distribution along the chromosomes vary considerably among animal species, including closely related species. Several hypotheses concerning the adaptive value and evolution of these variations were proposed. It was supposed that the recombination patterns of the species’ genomes are influenced by their phylogenetic history and ecology. However, most original data were obtained from mammals. The mammals show high karyological variability, which strongly influences the recombination patterns. Therefore it is important to study recombination rate and distribution in more karyologically stable taxa, such as reptiles and birds. We used immunolocalization of SYCP3, the protein of the lateral element of the synaptonemal complex (SC), centromere proteins and the mismatch-repair protein MLH1, which is associated with the recombination nodules, at the synaptonemal complex spreads of prophase oocytes of two tern species, black tern (Chlidonias niger) and common tern (Sterna hirundo). We first described the karyotype of Ch. niger (2n = 74, FN= 94) and identified suggestive rearrangements by which its karyotype differs from that of S. hirundo (2n = 68, FN = 90). We found that these species significantly differed by the numbers of the MLH1 foci per cell (Ch. niger: 53.0±4.2; S. hirundo: 44.1±5.0). We showed that the difference in the crossover numbers per cell was determined by the difference in the SC length (total and of individual bivalents) and by chromosomal rearrangements, which also influenced the distributions of crossover sites along the chromosomes. The difference in recombination patterns was higher between the rearranged homeologues than between the non-rearranged ones. We investigated the synaptic patterns of the heteromor phic Z and W chromosomes, localized the pseudoautosomal regions and estimated their lengths. In spite of several autosomal rearrangements, which differentiate these species, the structure and synaptic patterns of the sex chromosomes have not changed over 9 MY, which have passed since the moment of divergence between the genera Sterna and Chlidonias.

Wind differentiates reproduction in the non-expansive Black Tern Chlidonias niger and the expansive White-winged Tern Chlidonias leucopterus

Identifying the key factors governing the expansion of a species’ range is difficult because of the multiple interactions of environmental and biological factors. Among the biological factors are breeding parameters, which at the edge of a species’ range may indicate the traits involved in limiting species distribution. To evaluate whether the hatching success of two sympatric species of terns was dependent on weather parameters, a study was carried out in the valley of the River Bug in eastern Poland. During 2007–2010, nine colonies with 113 clutches of White-winged Tern (CHL, an expansive species, new to the region since 1997) and 92 clutches of Black Tern (CHN, a non-expansive species, nesting in stable numbers in this region for many years) were monitored. CHN arrived on average 9 days earlier than CHL. While CHN arrived in east-central Poland earlier and earlier during the 1998–2013 period, no such trend was recorded for CHL. The clutch initiation median in CHL was 8 days later than in CHN. The hatching success of CHL was statistically less than that of CHN (41.6 vs. 69.6%). A general discriminant analysis model showed that successful CHL clutches depended on the maximum daytime wind speed (strong winds can be disastrous for breeding terns), colony identity and clutch initiation date. In the case of CHN, none of these factors had a statistically significant influence on hatching success, although the clutch initiation date was very close to being significant. These results suggest that a species which nested in the same location for a long time in relation to ambient weather conditions has higher hatching success than the one which is in the process of expanding its distribution range.

Local Black TernChlidonias nigerPopulation Trends in Relation to Nest Platform Provisioning

The population of Black Terns in The Netherlands strongly declined in the period from 1950 to 1980. In recent years numbers have been more stable. The supply of artificial nest platforms has successfully attracted breeding Black Terns, and 80% now breed on platforms. In this paper we describe the development in numbers and breeding success of a Black Tern population in The Netherlands over the period 1982–2015, where ample nest platforms have been supplied over time. Using this database we question whether we can increase the breeding population by supplying platforms. We are uncertain whether tern numbers responded to an increase in nest platforms, or whether researchers responded to an increase in tern numbers by putting out more nest platforms. We analyse (1) settlement and breeding success in relation to nesting substrate, (2) the covariation between breeding numbers and platform numbers over time and space, and (3) the density dependence of settlement and breeding success. Against this background we analyse whether the annual change in platform numbers is followed by a change in tern numbers, as would be expected if there was a causal link between the two. We show that in our study area reproduction on artificial platforms was higher than on natural substrate and that the tern population in the whole study area increased over the study period. This increase in numbers was associated with an increase in the number of platforms, as expected when platforms affect tern numbers. Settlement in the first year after introduction of the platforms was higher, but in later years there was no correlation between annual change in the number of platforms and annual change in the number of breeding pairs. We did not detect a decline in the number of fledglings produced per pair with increasing tern breeding density. In conclusion, although the general pattern suggests positive effects of platform numbers on tern numbers, we are strictly speaking not able to show that supplying nest platforms caused the increase in the local Black Tern population over the study period. The answer awaits large scale experiments with control areas and individually marked birds to quantify survival and dispersal.

Range-wide patterns of population differentiation of Eurasian Black Terns (Chlidonias niger niger) related to use of discrete post-nuptial staging sites

The Eurasian Black Tern, Chlidonias niger niger, nests in marshes continuously distributed across Eurasia, but migration routes, staging sites, and non-breeding distributions are not well understood. In western Europe some populations have declined substantially over several decades (>90%), thus a more complete understanding of breeding site connectivity and migratory routes is needed. We collected tissue samples of terns in breeding colonies in the Netherlands, Latvia, southern Ukraine, eastern Siberian Russia, and from individuals at one important post-nuptial staging site in The Netherlands. Microsatellite data suggest significant differentiation among all breeding sites and the pattern is supported by differences among sites in most morphological measures. Conversely, mitochondrial DNA suggests similarity and population expansion especially from the region around Ukraine. We assigned 70% of the birds sampled on the staging site to the Netherlands/Latvia breeding population, but none to the southern Ukrainian or eastern Russian population. Our data indicated limited contact at post-nuptial staging sites contribute to genetic structure among breeding sites for this species. Our study demonstrates the utility of genetic data in migration studies to delineate migratory flyways and highlight the importance of specific staging sites to specific breeding subpopulations.

Validation of landscape suitability indices for Black Terns (Chlidonias niger) in the U.S. Great Lakes region

ABSTRACT Remotely sensed land cover data enable characterization of avian habitat over large spatial scales, which can be applied to regional conservation planning. Black Terns (Chlidonias niger) have been declining in the U.S. Great Lakes region for decades. Although causes of the decline are not well understood, habitat loss and degradation are viewed as major barriers to recovery. The Upper Mississippi River and Great Lakes Region Joint Venture, a partnership for bird conservation in the Upper Midwest, developed a landscape suitability index for the wetland-breeding Black Tern based on remotely sensed land cover to choose habitat to enhance or restore. We tested the validity of this index and compared it to an alternative index we constructed from results of field surveys. Over 2 breeding seasons, we surveyed for presence of Black Tern breeding colonies in 158 wetlands across the Great Lakes region and compared our findings with predictions of the existing index. We used our first season of surveys, nu...

Brood sex ratio in expansive and non-expansive tern species in east-central Poland

Capsule Evidence from two tern species does not support the theory that species in expansion should bias their brood sex ratios towards the more dispersing sex.Aims Sex ratio theory predicts that when a species is in expansion, the sex ratio should be biased towards the more dispersing sex. We compared the sex ratio of nestlings in two closely related species of terns, characterized by different expansion rates: the White-winged Tern Chlidonias leucopterus (an expansive species) and the Black Tern Chlidonias niger (a non-expansive species).Methods The fieldwork was carried out in the valleys of the Rivers Bug and Narew in east-central Poland, from 2008 to 2014, during which time eight White-winged Tern colonies and ten Black Tern colonies were monitored. Nest inspections began around 15–20 May, when the first eggs were laid, and continued until mid-July, when the last nestlings were 7–20 days old.Results The nestling sex ratios were similar in both species, and the differences between number of females and males were not significant (White-winged Tern: 56.6% females vs. 43.4% males; Black Tern: 57.4% females vs. 42.6% males).Conclusions The lack of differences in nestling sex ratio in these species may be due to the cessation of the White-winged Tern's expansion in this area or because the sex ratio is characteristic of Sternidae species, as similar results have been reported for other tern species.