Non-breeding Birds Research Articles

Spatial structure of breeding settlements of the Snowy Owl (<i>Bubo scandiacus</i>, Strigiformes, Strigidae) in the tundra of the Taimyr Peninsula

Data on Snowy Owl breeding settlements and encounters in the tundra were analyzed for the periods of 1996–2007, 2012, 2014–2020 in the vicinities of the Medusa Bay (73°21ʹN, 80°32ʹE), northwestern Taimyr Peninsula, Siberia. Breeding Snowy Owls were detected in 1996, 1999, 2002, 2004, 2005, 2007, 2014, 2016 and 2019. The spatial distribution of nests, summarized for 9 breeding years, appear to be grouped (clustered). This means that the spatial population structure of Snowy Owls mostly consists of permanent breeding sites, or territorial cells. However, the distribution of these cells in the tundra area is uniform. The reasons for such an attraction to the same sites in the tundra that fail to differ from many others are not clear yet. The existing version of the “signal field” theory cannot account for this attraction: owls very rarely occupy previously used nest sites, definitely preferring new entire breeding places within these territorial cells. In fact the basis of so dividing the breeding area into permanent territorial cells and of choosing definite ones among them seems to indicate that birds are oriented to certain yet unknown features of the environment rather than only to the ecological characteristics of the habitat and/or to tracks from the previous bird activity. A summarized distribution of the Snowy Owl encounters of non-breeding birds was clustered, as well. The distribution of these clusters across the plain tundra (in rugged areas non-breeders occurred very rarely) appeared to be random. In different seasons, regardless of the breeding status, Snowy Owls may behave in very different ways: they may tend to pose closer to other owls or try to stay farther away; they may start breeding at very low lemming numbers or, vice versa, they do not breed in good nutritional conditions.

Behavioural responses of a trans-hemispheric migrant to climate oscillation.

Large-scale climatic fluctuations, such as the El Niño-Southern Oscillation, can have dramatic effects on ocean ecosystem productivity. Many mobile species breeding in temperate or higher latitudes escape the extremes of seasonal climate variation through long-distance, even trans-global migration, but how they deal with, or are affected by, such longer phased climate fluctuations is less understood. To investigate how a long-lived migratory species might respond to such periodic environmental change we collected and analysed a 13 year biologging dataset for a trans-equatorial migrant, the Manx shearwater (Puffinus puffinus). Our primary finding was that in El Niño years, non-breeding birds were at more northerly (lower) latitudes than in La Niña years, a response attributable to individual flexibility in migratory destinations. Daily time spent foraging varied in concert with this latitudinal shift, with birds foraging less in El Niño years. Secondarily, we found that in subsequent breeding, a hemisphere away, El Niño years saw a reduction in foraging time and chick provisioning rates: effects that could not be attributed to conditions at their breeding grounds in the North Atlantic. Thus, in a highly migratory animal, individuals may adjust to fluctuating non-breeding conditions but still experience cascading carry over effects on subsequent behaviour.

Exposure of wetlands important for nonbreeding waterbirds to sea-level rise in the Mediterranean.

Sea-level rise (SLR) is expected to cause major changes to coastal wetlands, which are among the world's most vulnerable ecosystems and are critical for nonbreeding waterbirds. Because strategies for adaptation to SLR, such as nature-based solutions and designation of protected areas, can locally reduce the negative effects of coastal flooding under SLR on coastal wetlands, it is crucial to prioritize adaptation efforts, especially for wetlands of international importance for biodiversity. We assessed the exposure of coastal wetlands important for nonbreeding waterbirds to projected SLR along the Mediterranean coasts of 8 countries by modeling future coastal flooding under 7 scenarios of SLR by 2100 (from 44- to 161-cm rise) with a static inundation approach. Exposure to coastal flooding under future SLR was assessed for 938 Mediterranean coastal sites (≤30km from the coastline) where 145 species of nonbreeding birds were monitored as part of the International Waterbird Census and for which the monitoring area was delineated by a polygon (64.3% of the coastal sites monitored in the Mediterranean region). Thirty-four percent of sites were threatened by future SLR, even under the most optimistic scenarios. Protected study sites and study sites of international importance for waterbirds were, respectively, 1.5 and 2 times more exposed to SLR than the other sites under the most optimistic scenario. Accordingly, we advocate for the development of a prioritization scheme to be applied to these wetlands for the implementation of strategies for adaptation to SLR to anticipate the effects of coastal flooding. Our study provides major guidance for conservation planning under global change in several countries of the Mediterranean region.

Effects of human disturbance on detectability of non-breeding birds in urban green areas

Animals adapted to disturbed habitats have evolved multiple behavioural strategies, spanning from hiding to displacing to less disturbed microhabitats. Urban areas pose new evolutionary challenges since animals often need to deal with novel environmental conditions. In this context, urban parks may constitute biodiversity hotspots within the concrete jungle. Nonetheless, the recent increase in recreational activities in urban parks potentially puzzles the ability of urban-dwelling animals to exploit these environments. In this study, we evaluated the effect of human disturbance and other contextual variables on the activity patterns of four bird species commonly found in European urban parks, covering a wide range of ecological characteristics: the blackbird (Turdus merula), the hooded crow (Corvus cornix), the Eurasian robin (Erithacus rubecula), and the wood pigeon (Columba palumbus). We performed repeated counts of these bird species in six urban parks in northern Italy and we fitted Bayesian N-mixture models to estimate the relationship between detection probability and human disturbance (number of people present in the park), phenology (date and time of the day), and weather conditions (temperature and precipitation). For all the species but the blackbird, we found a negative relationship between the number of people present in the park and the detection probability of the focal species. We also found species-specific effects of both phenology and weather conditions on the detection probability. Our results suggest that urban dwelling species can finely modulate their activity patterns in response to the level of human disturbance, suggesting a possible key role of behavioural phenotypic plasticity. Furthermore, uncovering patterns of detectability of urban fauna can help in planning biodiversity monitoring and conservation, as it provides useful information to carry out surveys when the probability of detecting individuals is highest, optimising resource investments and reliability of biodiversity estimates.

The Elevational Gradient of Bird Beta Diversity in the Meili Snow Mountains, Yunnan Province, China.

Understanding the elevational patterns of beta diversity in mountain regions is a long-standing problem in biogeography and ecology. Previous research has generally focused on the taxonomy facet on a large scale, but was limited with regard to multi-facet beta diversity. Accordingly, we constructed a multi-dimensional (taxonomic/phylogenetic/functional) framework to analyze the underlying mechanisms of beta diversity. Within an approximately 2000 m altitudinal range (from 2027 m to 3944 m) along the eastern slope of the Meili Snow Mountains in Deqin County, Yunnan Province, China, we performed field surveys of breeding and non-breeding birds in September/2011 and May/2012, respectively. In total, 132 bird species were recorded during the fieldwork. The results indicated that taxonomic beta diversity contributed 56% of the bird species diversity, and its turnover process dominated the altitudinal pattern of taxon beta diversity; beta phylogenetic diversity contributed 42% of the bird phylogenetic diversity, and its turnover process also appeared to be stronger than the nestedness. For both taxonomy and phylogeny, the null models standardized measures (SES.βsim/SES.βsne/SES.βsor) of paired dissimilarities between elevation zones all showed statistically significant differences (p ≤ 0.05) and were higher than expected (SES.β > 0). However, standardized functional beta diversity showed convergence along the elevational gradient with no significant change. Moreover, the functional beta diversity contributed 50% of the bird functional diversity; there was no significant difference between the turnover and the nestedness-resultant component. Based on these results, we discerned that taxonomic and phylogenetic beta diversity patterns among the elevational zone were overdispersed, which indicated that limiting similarity dominated the turnover process among the bird species and phylogenetic communities in the Meili Snow Mountains.

Geolocator-tracking seabird migration and moult reveal large-scale, temperature-driven isoscapes in the NE Atlantic.

By combining precision satellite-tracking with blood sampling, seabirds canbeusedto validate marine carbon and nitrogen isoscapes, but it is unclear whether a comparable approach using low-precision light-level geolocators (GLS) and feather sampling can be similarly effective. Here we used GLS to identify wintering areas of northern gannets (Morus bassanus) and sampled winter grown feathers (confirmed from image analysis of non-breeding birds) to test for spatial gradients in δ13 C and δ15 N in the NE Atlantic. By matching winter-grown feathers with the non-breeding location of tracked birds we found latitudinal gradients in δ13 C and δ15 N in neritic waters. Moreover, isotopic patterns were best explained by sea surface temperature. Similar isotope gradients were found in fish muscle sampled at local ports. Our study reveals the potential of using seabird GLS and feathers to reconstruct large-scale isotopic patterns.

THE TUNDRA SWAN, <i>CYGNUS COLUMBIANUS</i> (ANATIDAE), IN THE EASTERN ASIAN ARCTIC: TRENDS AND RANGES OF DIFFERENT FLYWAY POPULATIONS

The tundra of the eastern Asian Arctic is inhabited by at least three flyway populations of the Tundra swan: the East Asian continental migratory flyway population of C. c. bewickii; the western Pacific flyway population of C. c. bewickii, and the western (American) flyway population of C. c. columbianus. The main objective of the present paper is to assess population trends by comparing information on the historical (the only one in the tundra of northeastern Asia) bird aerial survey in 1993–1995 with the data of our aerial survey held in 2020–2021. Another aim was to estimate the proportion of breeding birds in different flyway populations. The size of the zone of intergradation C. c. bewickii and C. c. columbianus in Chukotka and the level of hybridization have so far remained poorly studied, this issue required clarification. Aerial survey data for 2020–2021 were processed using QantumGIS 9.16.5 software. The system included the following layers: a vector layer of the world map; routes of aerial surveys for 2020 and 2021; and polygons of counts for 1993–1995. The system made it possible to calculate the length of the survey. Estimates for each region were calculated for the extrapolation area given in the historical survey. Between 1993–1995 and 2020–2021, an increase in the numbers of all three flyway populations of the Tundra swan was revealed on the breeding grounds. The East Asian continental flyway population increased 3.86 times, vs. 3.05 times for the West Pacific flyway population (while the documented growth of this population was 2.1 times, according to mid-winter counts over the same period). The Western (American) flyway population grew 2.5 times. We believe that the northern border of the summer range of the Tundra swan has significantly shifted to the north, following the summer climate change and the northward shift of the subarctic tundra zone. Registration of nests and broods in areas where only non-breeding birds were recorded during the historical survey is additional evidence of a northward displacement of the range. Kymyneyveem R (about 175.6° W) borders the areas of dominance of C. c. bewickii and C. c. columbianus. The switch in dominance has been triggered off, as there is no zone where both subspecies would occur in equal proportions. The overlap area of both subspecies extends for 600 km along the Arctic coast.

Historical changes of biodiversity in Baikal Siberia and dynamics of nest settlements of the Great Cormorant (Phalacrocorax carbo L., 1758) in the first quarter of the XXI century

The article presents the history of nesting, disappearance from the fauna and the current spatial distribution of Great Cormorant (Phalacrocorax carbo L., 1758) breeding colonies in Baikal Siberia. The main research sites were the Selenga River Delta, Strait of the Maloye More and islands of the Chivyrkuy Bay, Upper Angara Bay on Baikal Lake; the Upper Angara and Barguzin hollows, Gusinoe Lake in the Pribaikalye and Transbaikalye, where this species once lived according to well-known literary sources in the XVII to the middle of the XX centuries. Direct accounting of newly nesting birds after a 50-year absence in known colonies with young birds that flew out by autumn, as well a non-breeding birds, allowed us to estimate the total number of cormorants in 2021 on Baikal Lake. It amounted to 39-40 thousand birds, which indicates the settlement of the species in the Baikal Lake ecosystem and population stabilization in accordance with the environmental ecological capacity.

Precipitation Dominates the Distribution of Species Richness on the Kunlun–Pamir Plateau

The Kunlun–Pamir Plateau is a globally irreplaceable biodiversity reserve, yet it is still unclear what causes the distribution of species richness. Here, we relied on the productivity and the water–energy dynamics hypotheses to investigate the distribution pattern of species richness (and its determinants) in the Kunlun–Pamir Plateau. The productivity hypothesis is mainly based on five MODIS products (NDVI, EVI, FPAR, LAI and GPP), which were calculated for three Dynamic Habitat Indices (DHIs): (1) cumulative productivity (CumDHI), (2) minimum productivity (MinDHI) and (3) intra-annual variation productivity (VarDHI). The CumDHI was applied to assess whether or not more energy has a higher species richness value. The MinDHI was used to determine and evaluate the higher minimums, leading to a higher species richness. The VarDHI was the annual variation value in productivity and was utilized to assess if the reduced intra-annual variability triggers a higher species richness. We found that the DHIs based on the FPAR correlated slightly higher with the mammal, bird, breeding bird and non-breeding bird richness (than those based on the other four DHIs, and the values were 0.24, 0.25, 0.24 and 0.01, respectively). The correlation between the climate variables and the mammals, birds, breeding birds and non-breeding birds was bigger at 0.24, 0.54, 0.54 and 0.02, respectively, and was mainly dominated by the precipitation-related climatic factors. The water–energy dynamic hypothesis is better suited to the Kunlun–Pamir Plateau than the productivity hypothesis. Our results might provide valuable information regarding the biodiversity conservation in this region.

Diets for captive breeding and hacking of saker falcons (Falco cherrug) in Bulgaria

Abstract. With saker falcon populations on the mend globally, and in Bulgaria, special caution is taken to ensure the best possible care of the birds in their breeding programmes. Diets play a particularly important role as they affect the health of not only the breeding pairs, but also the young birds. With the ultimate goal for the captive-bred sakers being to reestablish viable saker falcon populations, releasing healthy falcons is paramount. As part of the ongoing saker falcon reintroduction efforts in Bulgaria, special emphasis was placed on well-rounded diets carefully tailored to the species, and the accompanying proper sanitation procedures. Outlined are best practices concerning the variety of dietary regimes for saker falcons in captivity and for released falcons based on their biology and behaviour. In captivity the meals were different for non-breeding birds, breeding birds, for nesting birds, and for birds with chicks in the nest. The hacked juvenile saker falcons had a change in diet every two weeks – starting with food similar to the one in the breeding facilities, to the more natural for the species meals. The different techniques aimed at replicating wild conditions resulted in a natural breeding behaviour for the saker falcons kept in captivity, and successful adaptation for the released juveniles. The meal preparation methods kept the risk of food-transmitted diseases to a minimum.

Diet of adult and immature imperial cormorants, Leucocarbo atriceps, from southern Patagonia. A combined dietary approach and an exploratory analysis of stable isotopes of pellet membrane

The use of combined conventional and stable isotope analyses (SIA) to study the diet of seabirds has become very frequent. Unfortunately, information on the trophic ecology of immature seabirds remains scarce because the sampling of tissues to perform SIA is often very limited due to the difficulty to capture these birds. The koilin membrane, which covers the regurgitated pellet casts of some seabirds, could offer an interesting non-intrusive alternative tissue to perform SIA. In this two-year study of the diet of imperial cormorants in southern Patagonia, we (1) compare the diets of breeding and non-breeding birds through conventional pellet analysis; (2) describe the diet of breeding adults and chicks through a combined method of pellet analysis and whole blood SIA; and finally, (3) compare SIA values of breeding adults obtained from blood with those obtained from koilin membranes. We found that immature individuals incorporated abundant invertebrate taxons, compared with breeding adults which relied mainly on fish. Younger and inexperienced individuals, which are not under the constraint to feed chicks, are feeding on more predictable, but lower trophic and less energetic prey. By comparing the stable isotope values of koilin and blood in breeding adults, a correlated interannual difference between the two seasons was found. Under the light of our results, the koilin offers an encouraging alternative to blood in the study of trophic ecology, particularly for ages or stages in which capture is not possible.

Coastal bird community response to dredge‐spoil tidal marsh restoration at New Round Island, Mississippi, U.S.A.

The northern Gulf of Mexico has been the focus of many coastal habitat restoration projects in the wake of new funding streams stemming from the settlement of the 2010 Deepwater Horizon oil spill litigation. One such project was the creation of New Round Island (RNDI) in Mississippi, a 86 ha island created using dredge material in 2017. The island design incorporated a novel U‐shaped sand berm with multiple interconnected containment sells. In this study we sought to document changes in relative abundance of various coastal bird species. We conducted surveys for breeding and nonbreeding birds from June 2017 to May 2021, and we conducted nonbreeding surveys at two reference sites for comparison. Breeding bird numbers were dominated by colonial nesting species in years 1 and 2, which subsequently declined as vegetation cover increased. Solitary nesting species increased over time, with Wilson's Plover (Charadrius wilsonia) nest count increasing from zero in year 1 to 29 in year 5. Nonbreeding shorebird counts peaked in years 1–2 and subsequently declined, although shorebird counts also decreased at the reference sites. Relative abundance of waders (Ardeidae), rallids (Rallidae), and passerines (Passeriformes and allies) increased in comparison to reference sites. This study demonstrates the short‐term benefits of this U‐shaped island design to early‐succession breeding species and nonbreeding shorebirds shortly after construction, with longer‐term benefits to breeding Wilson's Plover and to marsh birds as vegetation fills in.

The Tricolored Blackbird in Washington State: First Assessment of Status and Distribution

Breeding of the Tricolored Blackbird (Agelaius tricolor) in Washington State was first reported in 1998, but since then the species’ status and population trends have been poorly documented. I reviewed available data and found reliable reports of breeding at six locations, all in the Columbia Basin ecoregion, and additional reports of nonbreeding birds in 11 counties statewide. Breeding colonies were small, averaging 34 birds. All colonies were in emergent vegetation, and birds moved among them over the 24 years covered by this assessment. The relatively arid environment of the Columbia Basin, the limited extent of wetlands suitable for nesting, and the intensification of agriculture, implying a reduction in insect populations, likely inhibit the expansion of the Tricolored Blackbird’s range in Washington. A systematic survey of known and suitable breeding locations within the Columbia Basin ecoregion, more intensive monitoring of colonies during the breeding season, an assessment of foraging habitats, and a review of the Tricolored Blackbird in the Washington State Wildlife Action Plan for 2025 should be the next steps in assessing the status and trends of the species.

Analysis of the Recovery Data of the Great Cormorant Phalacrocorax carbo Ringed in the Russian Federation and on the Territory of Former Soviet States in 1939–2014

This study is based on recoveries of c. 86,850 Great Cormorants ringed in the Russian Federation during 1939–2014. Data were obtained from the Bird Ringing Centre of Russia. During 1939 to 2014 a total of 1667 Cormorant recoveries (1.9%) were added to the ringing database. The majority of the recoveries were made in the Caspian Sea, Azov Sea, Black Sea, Baltic Sea and in Kazakhstan inland waterbodies, including the Aral Sea (seven recoveries), Lake Alakol (46), Lake Balkhash (28), Kapchagay Reservoir (10) and Lake Zaysan (5). Non-breeding birds (assuming breeding at age > 3 years) comprised 89% of ring recoveries from 1939 to 1974, 95% from 1975 to 1990 and 100% from 1991 to 2014. This study is the first to describe the migration patterns for this species on a continental scale. From Kaliningrad in the west to Vladivostok in the east seven mega clusters of waterbodies and wetlands exist where Cormorants breed and were ringed. Although showing some overlap, birds belonging to a certain cluster were recovered in distinct wintering areas, often more than 2000 km from the breeding areas and separated by high mountain ranges. The general migration pattern is discussed for four geographic regions. The occurrence of east–west migration patterns is briefly discussed and deserves further study as well as the role of high mountain ridges possibly shaping the movements between summer and winter areas.

Drones, automatic counting tools, and artificial neural networks in wildlife population censusing.

The use of a drone to count the flock sizes of 33 species of waterbirds during the breeding and non‐breeding periods was investigated.In 96% of 343 cases, drone counting was successful. 18.8% of non‐breeding birds and 3.6% of breeding birds exhibited adverse reactions: the former birds were flushed, whereas the latter attempted to attack the drone.The automatic counting of birds was best done with ImageJ/Fiji microbiology software – the average counting rate was 100 birds in 64 s.Machine learning using neural network algorithms proved to be an effective and quick way of counting birds – 100 birds in 7 s. However, the preparation of images and machine learning time is time‐consuming, so this method is recommended only for large data sets and large bird assemblages.The responsible study of wildlife using a drone should only be carried out by persons experienced in the biology and behavior of the target animals.

Physiological parameters of a plover during nonbreeding and breeding seasons in Patagonia, Argentina

Migratory shorebirds are the most threatened avian species due to the effects of human activities and climate change. Physiological parameters are useful to evaluate the health status of free-living animals. Here we investigated lymphocytes, heterophils, heterophils/lymphocytes, and glucose for female and male Two-banded Plovers (Charadrius falklandicus Latham, 1790) during nonbreeding (body moult) and breeding (incubation) seasons in coastal areas of northern Patagonia, Argentina. We also measured corticosterone for the first time for this species during the breeding season. Nonbreeding Two-banded Plovers were more likely to have higher physiological measurements that were not dependent on body moult nor body condition, being similar between sexes. Differences found in glucose are likely related to recent feeding in nonbreeding birds compared with fasting during incubation. The gregarious nonbreeding behaviour in comparison with the isolated breeding pairs would increase the risk of acquiring parasites and (or) pathogens inducing a response of the immune system reflected in higher values of lymphocytes. Baseline corticosterone during breeding was similar between sexes and were lower compared with other values reported for breeding plovers. Two-banded Plovers undergo energetically demanding physiological changes during the nonbreeding stage, strengthening the idea that conservation of the environmental resources at these locations may be more important than previously thought.

Immune function differs among tropical environments but is not downregulated during reproduction in three\xa0year-round breeding equatorial lark populations

Seasonal variation in immune function can be attributed to life history trade-offs, and to variation in environmental conditions. However, because phenological stages and environmental conditions co-vary in temperate and arctic zones, their separate contributions have not been determined. We compared immune function and body mass of incubating (female only), chick-feeding (female and male), and non-breeding (female and male) red-capped larks Calandrella cinerea breeding year-round in three tropical equatorial (Kenya) environments with distinct climates. We measured four immune indices: haptoglobin, nitric oxide, agglutination, and lysis. To confirm that variation in immune function between breeding (i.e., incubating or chick-feeding) and non-breeding was not confounded by environmental conditions, we tested if rainfall, average minimum temperature (Tmin), and average maximum temperature (Tmax) differed during sampling times among the three breeding statuses per location. Tmin and Tmax differed between chick-feeding and non-breeding, suggesting that birds utilized environmental conditions differently in different locations for reproduction. Immune indices did not differ between incubating, chick-feeding and non-breeding birds in all three locations. There were two exceptions: nitric oxide was higher during incubation in cool and wet South Kinangop, and it was higher during chick-feeding in the cool and dry North Kinangop compared to non-breeding birds in these locations. For nitric oxide, agglutination, and lysis, we found among-location differences within breeding stage. In equatorial tropical birds, variation in immune function seems to be better explained by among-location climate-induced environmental conditions than by breeding status. Our findings raise questions about how within-location environmental variation relates to and affects immune function.

Vocal repertoire, harmonic structure, and behavioural context in Red-throated Loon (<i>Gavia stellata</i>)

Among the five loon species (Gaviidae), Red-throated Loon (Gavia stellata) is the oldest lineage and is the most divergent in morphology and vocalizations. We substantially expand earlier description of calls for a nesting pair and non-breeding birds on Haida Gwaii, British Columbia, Canada. Three major calls used by the nesting pair (Quack, Wail, Plesiosaur) were all low frequency (700–3000 Hz) with multiple harmonics, calls that were also used by non-breeding birds without territories that overnight on freshwater lakes. Call duetting in the Wail and Plesiosaur, as well as sexually dimorphic frequencies and structure within the duets, typically occur in territorial display or pair interactions. The nesting pair used several calls audible only at short distances (Coo, Extended Coo, Staccato, Soft Raack) that were low frequency (200–1200 Hz), graded in behavioural intensity and that resulted in chick responses, including feeding or return to nest. A high amplitude Loud Raack was used by the female and is associated with flight incentives for pre-fledged chicks. Vocalizations of chicks, usually feeding solicitations to the adults, develop from simple chirps in the first week following hatch to more complex calls resembling the Wail and the Plesiosaur calls just prior to fledging. Although the majority of our acoustical descriptions are limited to a single nesting pair where sexes could be differentiated, these represent the first quantification of sound frequency, harmonic structure, and duration, most often associated with context-specific responses, and are suggestive of syntactical content to the vocal repertoire of this basal taxon.

Population Size, Behavior and Threats to Indian Skimmers (Rhynchops albicollis) at Their Largest Known Wintering Site

Bangladesh hosts most of what is left of Indian Skimmer (Rhynchops albicollis) populations, a globally endangered species. Each October-March from 2015-2020, 21 surveys of nonbreeding birds were made in Nijhum Dweep National Park, Bangladesh. High tide or evening roosts were counted from vantage points whenever a buildup or breakdown of skimmer concentrations was noticed, and site use noted by marking all observations of presence and activity on maps. The largest single count was 3,108 skimmers on 18 February 2020, constituting 30-50% of the known global population. Indian Skimmers mostly occurred in Damar Char West and at the tip of the Majher Char. Throughout the day with incoming tide, skimmers moved between preferred roosting areas to forage in the shallows. We describe a unique group-foraging strategy in which skimmers chase fish from deep water to shallow water along the shoreline. Circling high over the tidal channel, the flock of skimmers dives down in unison to just above the water surface, then spreading like a net towards the shore. Raptors caused disturbances to roosting skimmers, and we observed one instance of predation of a skimmer by a White-bellied Sea Eagle (Haliaeetus leucogaster). Human fishing activities disturbed nearshore foraging and shoreline roosting skimmers. We suggest protecting Damar Char West by regulating human activities to minimize disturbance from December to March.

Exceptional foraging plasticity in King Penguins (Aptenodytes patagonicus) from a recently established breeding site in Tierra del Fuego, Chile

Animals constantly test the borders of their own ecological niche and tend to expand their range, which is now additionally challenged by global climate change. Following human exploitation throughout the Southern Ocean in the 19th and the beginning of the 20th century, numbers of King Penguin breeding pairs have increased and former breeding sites have been re-colonized. Since 2010 a breeding colony became (re-)established at Bahía Inútil, Strait of Magellan, Tierra del Fuego, Chile. The aims of this study were to study the foraging ecology of King Penguins at this new breeding site, which is characterized by a set of different environmental variables as it is located within the confined environment of the Magellan Strait, more than 300 km from the open ocean. During the course of this study, thirty-two birds were successfully equipped with external devices that recorded 206 foraging trips by breeding and non-breeding birds. With one exception, all birds foraged throughout the year exclusively in the Magellan Strait with the main foraging areas located within 100 km from the colony. The diving activities of 15 King Penguins were recorded during 59 foraging trips, the deepest dive was 160 m and the longest dive lasted 6.75 mins. Based on a representative subsample of 3000 dives, mean dive depth was 32 ± 34 m and mean dive duration 117 ± 84 s. Accordingly, foraging trip durations throughout the year were significantly shorter than those recorded for conspecifics elsewhere. In accordance with these changes in foraging behavior, stomach contents from seven birds showed a mix of fish and squid, with Falkland sprats Sprattus fuegensis as the main prey item present in all samples. The implications of these behavioral adaptations are discussed with regard to this unusual confined foraging environment and predicted changes in the performance of King Penguins breeding elsewhere following global change.