Abundance In Spring Research Articles

Diversity and space-time dynamics of fish assemblages in a coastal lagoon, western Atlantic

The knowledge of the temporal and spatial dynamics in the composition of fish fauna makes it possible to identify patterns of occupation of ecosystems, providing a basis for evaluation and preservation of the local biodiversity. Monthly samplings were carried out at seven sites in a coastal lagoon, using a casting net, dip net and beach seine. A total of 4,110 individuals were collected, distributed in 23 families and 49 taxa of fish, with a predominance of Mugilliza, M.curema, Atherinellabrasiliensis, Micropogoniasfurnieri and Eucinostomusargenteus, corresponding to more than 80% total weight of all individuals caught. Regarding seasonality, greater abundances were recorded in fall, influenced by the high abundance of A.brasiliensis in this period. In addition to fall, this species was also abundant in summer. However, this pattern of dominance was different for the families Mugilidae and Gerreidae, with higher abundances in spring and summer, respectively. The highest abundances were found in the southern section of the lagoon, which are related to the high abundance of A.brasiliensis, M.liza and M.curema. In relation to the indices of average taxonomic distinctness and variation in the taxonomic distinctness, no significant differences were detected between the seasons of the year. Thus, the patterns of distribution and occurrence of fish in the lagoon were consistent with the patterns observed in Brazilian coastal lagoons and estuaries, as well as to the coastal shallow areas of the southeastern and southern regions.

Distribution and Characteristics of Halobates germanus Population in the Red Sea

We investigated the occurrence of the sea skater Halobates spp. from samples collected at a fixed time series station and from six cruises along the north-south extend of the Red Sea during 2016-2018. Halobates germanus White, 1883 was the only species found during our study, its distribution ranging between 17° 9´ N - 27° 27´ N and between 35° 67´ E - 41° 49´ E. Total H. germanus abundance ranged between zero to 158,610 individuals km-2 with a considerable temporal (at the fixed station) and spatial (cruises) variation. In general, nymphs of different instar stages dominated the population, followed by females and males. The sex ratio was female-biased, with a higher number of females than males. Presence and prevalence of eggs, exuviae (moults) and early nymphal stages indicate a year round breeding cycle by H. germanus. The apparent optimum temperature for H. germanus occurrence in the central Red Sea was at 28.2°C, corresponding to peak abundances in spring and fall. Absence of any significant correlation of the abundances with environmental parameters indicate relative resilience of H. germanus to changes in environmental conditions.

Life history, population structure and environmental modulation of Neomysis americana (Mysinae) in an intermittently open coastal lagoon of the South West Atlantic

Life history, seasonal population dynamics and spatial distribution pattern of the opossum shrimp Neomysis americana (Mysinae) were investigated during an annual cycle in the intermittently open coastal lagoon, Laguna de Rocha, Uruguay. Mysids were sampled by day with an epibenthic sled during the four seasons from January to November 2013. The study included estimates of the N. americana abundance and biomass distribution and its population structure (stages, sex ratio and size). Main environmental conditions were recorded at each period together with chlorophyll-a, and zooplankton abundance. All biotic estimations were converted to carbon units. N. americana occurred throughout the year with higher abundances in spring and its population was dominated by females. Results indicated that N. americana reproduces during all the year within the lagoon as juveniles were recorded along the sampled period with the occurrence of highest proportions in summer. Highest proportions of gravid females were recorded in spring. Wide tolerance and sustained reproduction under varying environmental conditions, as well as potential behavioural plasticity are traits prone to favour the further extension of the species to estuaries worldwide.

Spatial and temporal variation in mountain hare (Lepus timidus) abundance in relation to red grouse (Lagopus lagopus scotica) management in Scotland

Mountain hares (Lepus timidus) are regularly harvested on Scottish moorland managed for recreational hunting of red grouse (Lagopus lagopus scotica). There are concerns that large-scale culls of mountain hares on grouse moors are contributing to population declines of mountain hares in Scotland. We use hare data collected during red grouse counts in Scotland, to consider spatial and temporal variation in annual mountain hare indices of spring abundance in relation to different grouse management intensities, classified as either ‘Driven’ (driven grouse shooting), ‘Walked-up’ (walked-up shooting) or ‘Not-shot’ (where there was no grouse shooting interest). Trends in mountain hare abundance indices varied with region and grouse management intensity. Hare indices were higher and relatively stable on moors where driven grouse shooting was practised relative to lower indices and declines on moors where grouse were either walked-up or not shot. Abundance indices fluctuated over time in a quasi-cyclical manner, fluctuations being more pronounced where hares were more abundant, i.e. on driven grouse moors. Density-dependent processes such as resource competition and parasitism could explain greater fluctuations in areas where hare abundance indices were higher, whilst reductions in indices over time probably reflect sampling at decline phases of the cycle, particularly on driven moors, rather than being part of true long-term declines. Given our understanding of grouse moor management and mountain hare ecology, enhanced habitat management and control of generalist predators seem to be the most parsimonious explanation for higher abundances indices of mountain hare on driven grouse moors.

Population recovery of a common vole population (Microtus arvalis) after population collapse.

Population collapses in small mammals occur naturally after natural disasters and during multi-annual population fluctuations as well as after man-made intervention such as rodent management action. Although there has been extensive previous work on patterns and mechanisms of population fluctuations and cyclicity, little is known about population recovery after collapse. In Europe, the common vole (Microtus arvalis) is the major pest species in agriculture, damaging crops, competing with livestock and potentially posing a health risk to people. In this study, we investigated population recovery, recovery mechanism and recovery time of common vole populations after artificially inducing a collapse through rodenticide application. The rodenticide treatment reduced abundance in spring (by about 90%) but not in summer. Demographic data (age, sex-ratio, breeding activity) suggest that it was mostly immigration and not reproduction that led to population recovery after collapse. The findings indicate that rodenticide treatment should be conducted in spring before the main reproductive season starts. The treatment effect was transient and lasted for about 3months before immigration offset the initial reduction in population abundance. This indicates that immigration patterns should be considered by managing vole populations at an appropriate spatial scale and frequency to prevent rapid repopulation. © 2018 Society of Chemical Industry.

Diel, seasonal, and interannual patterns in mesozooplankton abundance in the Sargasso Sea

AbstractTemporal changes in mesozooplankton abundance affect planktonic food web interactions and biogeochemistry. We enumerated mesozooplankton from monthly day and night tows in the epipelagic zone at the Bermuda Atlantic Time-series Study (BATS) site in the Sargasso Sea (1999–2010). Abundances of each taxon were determined using a ZooScan imaging system and microscopy. Generalized linear models were used to determine environmental parameters that best explained abundance patterns. Taxa with pronounced diel vertical migration included euphausiids, amphipods, Limacina spp. pteropods, and other shelled pteropods. Taxa with a pronounced spring abundance peak included euphausiids, appendicularians, and Limacina spp., while harpacticoid copepods peaked in late summer, and calanoid copepods in late winter/early spring and summer. Many taxa increased in 2003, coincident with a diatom bloom and the largest primary production peak in the time series. Long-term, increasing trends occurred in calanoid and oncaeid copepods, and ostracods, with barnacle nauplii significantly increasing. Sub-decadal-scale climate oscillations and long-term warming may be driving decreases in shelled pteropods and appendicularians. Chaetognath abundance increased in response to increased density of a major prey taxon, calanoid copepods. Calanoid copepods and ostracods increased with increasing water column stratification index and the Atlantic Multidecadal Oscillation index, indicating warmer sea surface temperatures favour these taxa.

Mychonastes dominates the photosynthetic picoeukaryotes in Lake Poyang, a river-connected lake.

Lake Poyang, which is connected to the Yangtze River, is the largest freshwater lake in China and experiences large and frequent changes in water levels. The seasonal diversity and composition of photosynthetic picoeukaryotes (PPEs) in Lake Poyang were investigated from flow-cytometry-sorted samples using MiSeq high-throughput sequencing. Flow cytometric counting indicated that PPEs accounted for 97% of the total picophytoplankton abundance in spring, reaching a maximum value of 6.30 × 104 cellsmL-1. PPEs in Lake Poyang showed lower diversity than those in other investigated lakes in the lower reaches of the Yangtze River and were dominated by one OTU (66.29%) affiliated with Mychonastes (Chlorophyceae). Other minor classes of PPEs were found to be sporadically abundant in specific seasons, i.e. Chrysophyceae prevailed in spring and summer, while Eustigmatophyceae was mainly present in winter. This study reports coccal green algae of Mychonastes in Lake Poyang; additionally, these algae are reportedly representative of the prominent plankton in this river-connected lake ecosystem but are often overlooked due to their lack of morphological features. Finally, the sequencing results from the sorted samples of Lake Poyang revealed that the proportion of PPEs was quite low, with an average of 36% of total reads. Many OTUs belonging to heterotrophic picoeukaryotes were also identified in the sorted samples, most of which were affiliated with terrestrial fungi, including Basidiomycota and Ascomycota. The spores of these fungi can disperse in the aquatic environment during the flood seasons, yet their effect on PPEs is still unclear.

Small Mammals in the Northern Flint Hills Prairie: Overwinter Changes in Abundance

It is assumed that abundance of individual species of rodents and shrews in temperate regions decrease overwinter owing to winter mortality and cessation of reproduction. We wanted to examine this autumn versus spring pattern by using a 32-year long-term dataset from seven treatment sites on Konza Prairie Biological Station near Manhattan, Kansas, although we could not examine mortality or reproduction directly. We specifically wanted to determine first whether long-term patterns for species of small mammals showed that abundance decreased from autumn to spring and secondarily whether these patterns held among years and different habitat types. The decrease from autumn to spring was supported but, for individual species, varied from a 4% decrease to a 99–100% decrease. For the ten species that had at least one capture in either autumn or spring, the years in which autumn abundance was greater than that in spring varied among species; the range was from 44% of years for thirteen-lined ground squirrels (Ictidomys tridecemlineatus) to 100% for Elliot's short-tailed shrew (Blarina hylophaga). Likewise, patterns of decrease varied considerably among habitat types when spring abundance was compared as a percent of autumn abundance in the six most common species in seven research treatments. For example, spring abundance of deer mice (Peromyscus maniculatus), the most common small mammal, was only 52–54% of that in autumn for ungrazed sites that were burned annually, burned every 4 years or burned infrequently, whereas it was 105–130% of autumn abundance in bison-grazed sites that were burned annually or burned infrequently. Among the seven research treatments, the two least variable species decreasing in abundance from autumn to spring were Elliot's short-tailed shrews (spring populations were only 0–2% of those in autumn) and hispid cotton rats (Sigmodon hispidus; spring populations only 0–15% of those in autumn). Given the length of the study period, the high proportion of years that numbers of the common rodents increased from autumn to spring within the highly diverse mosaic of prairie studied suggests that a significant level of reproduction can occur between autumn and spring in many years, a life history trait that requires more study, especially in light of global climate change.

Seasonal succession of small planktonic eukaryotes inhabiting surface waters of a coastal upwelling system.

Small eukaryotes (0.2-20 μm cell-size) represent a significant fraction of the microbial plankton community in shelf waters of NW-Spain. The community composition of small eukaryotes living at the surface and at the base of the photic zone was analysed by means of 18S rDNA high-throughput sequencing on a circa-monthly basis over a 23 months period. Ostreococcus was the most abundant taxon in surface waters, showing marked peaks in read abundance in spring and late summer, while Syndiniales dominated at the base of the photic zone. A well-defined seasonal pattern of community composition, linked to the succession of the dominant taxa, was found in surface waters. Seasonality was less apparent at the base of the euphotic zone. Temporal changes in abiotic factors significantly correlated with changes in community composition in surface (r = 0.71) and at the base of the photic zone (r = 0.38). Changes in community composition significantly correlated with changes in community function-related variables (including biomass, primary production and respiration) only in surface water (r = 0.36). Co-occurrence network analyses revealed 45 significant interspecies associations among the 50 most abundant taxa with highly connected OTUs belonging to cryptophyceans. The network topology, with small-world characteristics, suggests a stabilizing role of biotic interactions to environmental disturbance.

Ecological control of exotic annuals in native C3 grass swards

AbstractWhile the mechanisms behind the control of exotic annuals by C4 native grasses on soils of low fertility are well understood, it is not clear how C3 native grasses sometimes achieve similar levels of control. In earlier research (Cole I. A., et al., 2016a, Aust. Ecol. 41, 40; Cole I. A., et al., 2016b, Restor. Ecol. 24, 354), the abundance of cool season exotic annuals waxed and waned over time, apparently in response to changes in the abundance of the tall C3 native grass (Austrostipa species) which at times dominated the understorey. This study used multiple linear regression and structural equation models to compare the relative influence of the abundance of the native grass sward (in autumn and spring), soil nitrate (in autumn) and the presence or absence of litter (in autumn) on the abundance in spring of exotic annual broadleafs and grasses. The most important controls of exotic annuals were native grass abundance and related soil nitrate reductions in autumn, when exotic annuals germinate. Another important control for exotic broadleafs was presence of litter in autumn. In contrast, the presence of litter promoted exotic annual grasses. Native grass abundance in spring (reflecting competition over the growing season of exotic annuals) appeared relatively unimportant. Key management objectives when attempting to control exotic annuals will be to maximize competition when exotic species are establishing by promoting the health and abundance of native grasses, and maintaining high levels of litter cover.

The polychaete, Paraprionospio pinnata, is a likely vector of domoic acid to the benthic food web in the northern Gulf of Mexico

A somewhat disparate, yet temporally cohesive, set of phytoplankton abundance, microphytobenthos, including the diatom Pseudo-nitzschia, benthic infauna, and sediment toxin data were used to develop a theory for the transfer of domoic acid (DA) from the toxic diatom to the benthos in the highly productive waters of the northern Gulf of Mexico near the Mississippi River plume. Archived samples and new data were used to test the theory that DA is likely to be incorporated into benthic consumers. High spring abundances of potentially toxic Pseudo-nitzschia diatoms were simultaneously present in the surface waters, bottom waters and on the seafloor. Examination of the gut contents of a typical deposit-feeding and suspension-feeding polychaete, Paraprionospio pinnata, during similar periods of high Pseudo-nitzschia abundance in surface water indicated consumption of the diatoms. Demersal fishes, particularly Atlantic croaker, are known to consume these polychaetes, with a potential for transfer of DA to even higher trophic levels. These findings warrant a theory to be tested with further studies about the trophic linkage of a phytoplankton toxin into the benthic food web.

Co-occurrence Networks Among Bacteria and Microbial Eukaryotes of Lake Baikal During a Spring Phytoplankton Bloom.

The pelagic zone of Lake Baikal is an ecological niche where phytoplankton bloom causes increasing microbial abundance in spring which plays a key role in carbon turnover in the freshwater lake. Co-occurrence patterns revealed among different microbes can be applied to predict interactions between the microbes and environmental conditions in the ecosystem. We used 454 pyrosequencing of 16S rRNA and 18S rRNA genes to study bacterial and microbial eukaryotic communities and their co-occurrence patterns at the pelagic zone of Lake Baikal during a spring phytoplankton bloom. We found that microbes within one domain mostly correlated positively with each other and are highly interconnected. The highly connected taxa in co-occurrence networks were operational taxonomic units (OTUs) of Actinobacteria, Bacteroidetes, Alphaproteobacteria, and autotrophic and unclassified Eukaryota which might be analogous to microbial keystone taxa. Constrained correspondence analysis revealed the relationships of bacterial and microbial eukaryotic communities with geographical location.

Implications of transformation to irregular silviculture for woodland birds: A stand wise comparison in an English broadleaf woodland

Woodland birds in Britain have undergone significant long term declines since the late 1960s, associated in particular with changes in woodland structure in general, and loss of early successional vegetation. Irregular, continuous canopy broadleaf management is a form of selective logging, very recently adopted in UK that produces woodlands with open canopies and substantial mid- and understorey growth. We examined spring and late winter bird densities, estimated using distance sampling, at 310 points in irregular, transitional (that being managed towards irregular), limited intervention, and coppice stands within a large working broad-leaf woodland in lowland southern Britain. Almost all understorey and canopy vegetation measures differed significantly across stand types. Ten of 20 species had highest spring abundance in irregular woodland, five in coppice, three in transitional, and just two in limited intervention. In winter, 5–6 species preferred each of limited intervention, irregular and transitional, while no species preferred coppice. Densities differed little across seasons except in Paridae where abundances increased in late winter during which limited intervention stands were used more by this group. Birds generally occupied similar niche positions and had similar niche breadths across seasons. Compared to under-managed woodlands, irregular silviculture in UK’s broadleaf woodlands is likely to enhance habitat quality for woodland birds, including several species of conservation concern e.g. marsh tit Poecile palustris which was twice as abundant in irregular stands as in any other stand type.

Populations of Commercial Molluscs within a Highly Biodiverse Marine Protected Area of the Northern Alboran Sea (W Mediterranean): Preferential Habitats, Seasonal Dynamics and Importance for Artisanal Fisheries

Seasonal dynamics and preferential sedimentary habitats of commercial molluscs have been studied in soft bottoms within the limits of the Special Area of Conservation (SAC) “Calahonda” (S Spain). This SAC harbours a high diversity of invertebrate communities, and it is located in a very touristy area of the littoral of Malaga and within the limits of one of the most productive shellfish fishing areas of the NW Alboran Sea. Here, the artisanal fishery targeting molluscs is a locally important activity because some species (e.g. Chamelea gallina, Callista chione, Donax trunculus) are highly demanded by locals and tourists and therefore reaching high commercial value. More than 200 molluscan species inhabit the soft bottoms of the SAC “Calahonda”, from which eight species collected in this study have economic value. The bivalve C. gallina was the most abundant and frequent commercial species, mainly at shallow fine and medium sand bottoms, followed by C. chione at coarse sand bottoms. Some species displayed higher abundance values of large or small size individuals at different depths, and most of them showed maximum abundances in spring and summer. Many invertebrate species associated with these soft bottoms are potentially very sensitive to dredging activities, especially echinoderms, decapods and cnidarians. Further research regarding the potential impact of fisheries on these assemblages would be desirable, especially considering the high biodiversity existing within this SAC and the increase of tourists in the last years.

Organic Micropollutant Removal by a Nanofiltration Pilot Plant used to Treat Spring Water from a Wastewater-Irrigated Valley

The abundance of freshwater springs in the Tula Valley is well documented. Large quantities of untreated wastewater from Mexico City are used for irrigation purposes, with the resultant emerging springs. Studies are needed to assess how safe water is to be supplied to the community. Comparative membrane studies were done on lab-scale, from which NF270 membrane was selected for a pilot plant in situ (critical flux 185Lm-2h-1). The system was successful at removing natural organic matter, hardness and pathogenic content. On-site membrane pretreatment using microfiltration and softening allowed moderate recoveries (60%) and slow permeate flux losses (124-90Lm-2h-1). Micropollutant (MP) removal was greater than 90% for most of the pharmaceuticals, hormones and phthalates using spiked spring water. However, moderate and variable removals were found when the concentrations of MPs were very low. Molecular structure and hydrophobicity were loosely related to the removal rates of the compounds evaluated, however an accumulating effect on the membrane might be key for higher MP removals. A threshold of concentration could have to be overcome to allow the removal process to achieve a better performance. In consequence, optimization of a large-scale process is the next step to take.

Co‐occurrence and seasonal and environmental distributions of the sandflies Lutzomyia longipalpis and Nyssomyia whitmani in the city of Puerto Iguazú, northeastern Argentina

The aim of this work was to study the distribution of Phlebotominae (Diptera: Psycodidade) abundance in time and space in an area in northeastern Argentina with vector transmission of visceral and tegumentary leishmaniasis. For this, 51 households were selected using a 'worst scenario' criterion where one light trap was set during two consecutive nights in peridomiciles in the transitions between the four seasons, and the environment was surveyed simultaneously. The relationships of phlebotomine assemblage structure and the most abundant species with seasonality and environmental variables were evaluated using a canonical correspondence analysis and generalized linear mixed models, respectively. A total of 5110 individuals were captured. Lutzomyia longipalpis (Lutz & Neiva, 1912) and Nyssomyia whitmani (Antunes & Coutinho, 1939) were the most abundant species captured in all samplings (98.3% of the total capture). The period of highest abundance of Lu. longipalpis was early autumn, and it was distributed in the most urbanized areas. Nyssomyia whitmani occupied mainly the less urbanized areas, showing peaks of abundance in early spring and summer. Other species were captured in low numbers and showed seasonal-spatial variations similar to those of Ny. whitmani. We confirmed Leishmania spp. vector persistence throughout the year in spatial patches of high abundance even during the less favorable season.

Apparent survival and cost of reproduction for White-lined Tanager (Tachyphonus rufus, Thraupidae) in the northern Atlantic Rainforest, Brazil.

Understanding latitudinal variation in avian life-history traits has been a focus of many demographic studies around the world. However, we still know little about annual or intra-annual demographic variation within tropical regions or about how factors such as breeding season and precipitation influence demographic rates. In this study, we estimated intra-annual apparent survival of the White-lined Tanager (Tachyphonus rufus) using capture-mark-recapture data from northeastern Brazil. We tested whether survival varied seasonally (breeding vs. non-breeding), with rainfall, by age and residence status in our study area. Intra-annual apparent survival was correlated with the reproductive cycle, being lower during the breeding (0.65 ± 0.16 SE) vs. the non-breeding season (0.97 ± 0.05 SE). The annual apparent survival (~0.6) was relatively low for a tropical species. In both years, we observed highest abundance in spring (November, 3.1–3.7 birds/ha) and lowest abundance in autumn-winter periods (May-August, 1.1–1.4 bird/ha). The low survival during the breeding season probably reflects the trade-off between survival and reproduction and the cost of reproduction. Our findings represent an advance in the understanding of the demography of tropical birds because we did not find a predicted high annual apparent survival, and we elucidated some aspects of intra-annual variation in survival. Further exploration of latitudinal variation in demographic traits, especially in diverse, but poorly known habitats is needed to fully vet and develop life history theories.

Analysis of the stress regime and tectonic evolution of the Azerbaijan Plateau, Northwestern Iran

The increasing number of earthquakes in recent decades in Northwestern Iran and the determination of the epicenters of these events makes possible to estimate accurately the changing tectonic regime using the Win-Tensor inversion focal mechanism program. For this purpose focal mechanism data were collected from various sources, including the Centroid Moment Tensor catalog (CMT). The focal mechanism and fault slip data were analyzed to determine change in the stress field up to the present day. The results showed that two stages of brittle deformation occurred in the region. The first stage was related to Eocene compression in NE–SW direction, which created compressional structures with NW–SE strike, including the North and South Bozgush, south Ahar and Gushedagh thrust belts. The second brittle stage began in the Miocene with NW–SE compression and caused developing thrusts with N–S trends that were active presently. These stress regimes were created by the counter-clockwise rotation of the Azerbaijan plateau caused by movement on strike slip faults and continuous compression between the Arabian plate, the south Caspian basin and the Caucasus region. Pliocene-Quaternary activity of the Sabalan and Sahand volcanoes as well as recent earthquakes occurred as a result of this displacement and rotational movement. The abundance of hot springs in the Ardebil, Hero Abad and Bostanabad areas also bore witness to this activity.

Inter-annual variability in spring abundance of adult Calanus finmarchicus from the overwintering population in the southeastern Norwegian Sea

Calanus finmarchicus is the dominant copepod species in the Norwegian Sea, where it plays a key role in the ecosystem by transferring energy from primary producers to higher trophic levels. This paper analyses a 17-year time series, 1996–2012, on C. finmarchicus collected within the Atlantic Water mass along the Svinøy transect in the southeastern Norwegian Sea. We use the spring abundance of adult as a proxy for the size of C. finmarchicus’ overwintered population. The inter-annual trend in spring abundance of adult C. finmarchicus in the 200–0m depth-stratum is assessed while accounting for spring population development to the adult stage represented by day of year for sampling, inter-annual changes in timing of population development, and spatial differences. For the most oceanic stations, a significant inter-annual trend in spring abundance of adult C. finmarchicus was revealed using generalized additive models (GAM). This trend primarily consists in an increase prior to year 2000 and a decrease between years 2000 and ca. 2011. For the stations closer to the coast, the identified inter-annual trend is a decrease during a longer period from the late 90s until ca. 2011. From 2000 to 2011, our estimates suggest a 50% decrease for the most oceanic stations, and as much as an 81% decrease for the stations closer to the coast. In addition the results suggest a consistent change in phenology over the years and the stations. The predicted spring peak of overwintered adult population abundance is suggested to become shorter by 3days, and the predicted maximum of abundance to take place 4days earlier over the 17years of the time-series. The results highlight significant changes in intensity and timing of the overwintered population of a key zooplankton species in the Norwegian Sea that may have important implications on the scale of an entire ecosystem.

Abundance, Distribution, and Geographic Origin of Non-breeding American Oystercatchers (Haematopus palliatus) in North Carolina, USA

Abstract. American Oystercatchers (Haematopus palliatus) are present in North Carolina, USA, year-round. About 6–7% of the total Western Atlantic population winters in North Carolina. To estimate numbers of American Oystercatchers present during the non-breeding season, four major concentration areas were surveyed in North Carolina, each with multiple roost sites, from 2008–2013. Abundance of American Oystercatchers remained generally stable during the study period. The Lower Cape Fear River area had the greatest number of American Oystercatchers in all seasons. Mean peak abundance was greatest during winter at all concentration areas. Peak winter abundance was 158 at Ocracoke Inlet, 265 in Back Sound, 187 in Masonboro Sound, and 470 on the Lower Cape Fear River. Fall abundance was generally greater than spring abundance at all concentration areas except Masonboro Sound. Most banded individuals observed were marked in North Carolina as chicks or nesting adults, and they exhibited fidelity to concentration...