Academic literature on the topic 'Waterbird guild'

Abstract Waterbirds constitute a prominent biota and reflect the ecosystem health and functionality of the freshwater wetlands. Documentation of the bird species assemblages of wetlands is therefore carried out as a part of monitoring of wetlands from a sustainability viewpoint. Using the emerging wetland of Purbasthali, West Bengal, India, as a model study area, the diversity of the associated bird species was estimated to supplement necessary information for conservation management of birds and ecosystems. The point count method was applied to count the waterbirds from each sighting location with a 25 m radius covering 360° arc and the counting period lasted 10 min for each site, and counts were made in the winter of 2016/2017. The data on the waterbirds encountered were recorded and subjected to diversity analysis, including the residential status, global population trend and feeding guilds. Apparently, the wetland was considered as suitable habitat for 27 waterbird species, which could be grouped under 24 genera, 10 families and 5 orders. Among these, the family Anatidae with maximum relative density and abundance dominated in the wetland. Out of the 27 recorded species, 5 species were widespread winter visitors, 3 species widespread resident, as well as, widespread winter visitors and 2 species were sparse local winter visitors. A globally near threatened species, the Black-headed Ibis (Threskiornis melanocephalus) was very common in the sampling sites. The waterbird assemblage in the wetland was dominated by carnivores followed by omnivores and herbivores. The abundance of the waterbirds with considerable variations in the foraging guild reflects availability and exploitation of multiple resources of the Purbasthali wetlands. Prominence in the differences in relative abundance of the different waterbirds could be linked with the heterogeneity in the habitat quality. The present information on waterbird assemblage calls for appropriate measures for conservation of the species and appropriate management of Purbasthali wetlands.

We counted waterbirds along a fixed route in the panhandle of the Okavango River in Mahango Game Reserve in the dry season during two seven-year periods (1991–1997 and 2000–2006). Palearctic migrants represented by 11 species in 1991–1997 and nine species in 2000–2006 together composed only a small percentage of all birds recorded in both periods. The two most numerous foraging guilds were birds foraging in shallow water and those foraging in deep water. The former guild was more numerous in 2000–2006, while the latter guild was more numerous in 1991–1997. The proportion of other foraging guilds varied little between the two periods. The most numerous diet guild was piscivores, they were more numerous in 1991–1997 than in 2000–2006. If the total numbers of birds of each particular species in the years 1991–1997 were pooled and compared with those for the years 2000–2006, then highly significant changes in their numbers between these periods could be seen for 53 out of 93 waterbird species. Over the timespan 1991–2006, 12 species significantly increased in numbers while one species, the Cattle Egret, declined; seven other species showed no significant changes in abundance. The increase can be linked to the volume of water flowing through the river. While during the years 1991–1997 the total volume measured at Mohembo was 45.9 km3 (SD = 1.43), during the years 2000–2006 the volume was 60.9 km3 (SD = 1.41). Diversity was very similar during the two periods (1991–1997: S = 1.4; 2000–2006: S = 1.3), with no difference in evenness. The striking feature is that species diversity and abundance of birds was far greater than any records from other southern African rivers to date.

Wetlands currently have high rates of degradation, with more than 70% lost globally. In the central Monte Desert, Argentina, they are a scarce and limited resource for the biodiversity which depends on them. Waterbirds have been used as biological indicators of wetlands because they respond to fluctuations in food resources and to environmental changes in the short term. Here we analyse the seasonal variations in the structure of the waterbird assemblage from a relict wetland in this region. We carried out censuses of waterbirds in a 6-year period (between 2009 and 2019) during the southern summer and winter. We recorded 1875 individuals of 33 species of waterbirds during the summer and 677 individuals of 29 species during the winter. The grouping patterns of the waterbird assemblages differed between seasons (R = 0.35; p < 0.01). Taxonomic diversity profiles showed greater diversity for all indexes (qD) during the summer. The guild of invertivorous and omnivorous waders had a greater abundance of individuals during the summer (p < 0.05) and, together with the surface-feeding herbivores, contributed to the 87% of the dissimilarity of the assemblages between seasons. Phoenicopterus chilensis was the only species registered as threatened with national and international extinction. Relict wetlands, such as Laguna del Viborón, still have attributes of community diversity and represent the last refuges for waterbirds of the central Monte Desert. The information gathered in this study will contribute to the guidelines for integrated management plans and monitoring programmes for the conservation of the wetland and its biodiversity.

Abstract Every year, the Coastal wetlands of North Africa support an important wintering waterbird population of many Palearctic and sub-Saharan species of various contrasting habitat requirements. In this study, we describe the habitat use by24 water-obligate species wintering in a coastal wetland of the Northeastern Algeria (the wetland of Lake Tonga), highlighting thereby the ecological mechanisms that support their coexistence and their resources partitioning. The analysis of resource exploitation (Relative frequency, Feinsinger niche breadth, Pianka niche overlap and Ivlev’s electivity indexes) showed that waterbird species inhabiting the lake wetland have several similarities in using the different habitat categories, which lead us to cluster them into 5 guilds (G1: one rails, two grebes and eight ducks; G2: five wading species and one gull; G3: three herons; G4: cormorants, mallards, and on gull; finally, G5: only one species Cattle egret (Bubulcus ibis).Almost all the species were specialists in resource utilization patterns (narrow niche breadths, both under 0.3) and therefore, vulnerable to fluctuations in resources, particularly the feeding habitats. Mean niche overlaps for all the pairs of species ranged from 0.05 to 0.68. The overall pattern in the community was higher niche overlaps between the species of a particular guild than those between other species. According to Ivlev’s electivity index, we found that only three microhabitats from seven were the most important for the discussed species, open water body was the most attractive, followed by meadows, muddy areas and floating- leafed vegetation. Similarities on habitat requirements derived from our region can provide important and optimal wetland management at multi-species assemblage level for this wetland and similar area around the African coast.

SummaryUnderground coal mining in the North China Plain has created large-scale subsidence wetlands that may attract waterbirds that use them as complementary habitats. However, no study has been conducted to understand avian use of these created wetlands, inhibiting the formulation of effective management plans. Here, we carried out 12 semi-monthly surveys in 55 subsidence wetlands during the 2016–2017 migration and wintering period and performed direct multivariate analyses, combined with variance partitioning, to test the effects of multi-scale habitat variables on the waterbird assemblages. A total of 89 349 waterbirds representing 60 species were recorded, with seasonal fluctuations in species richness and bird abundance. Waterbird community structures were shaped by four groups of variables at local, landscape and human levels with different effects among seasons. Anthropogenic disturbance was the most important factor group, negatively affecting most guilds. Waterbirds in this human-dominated environment are under a variety of potential threats that should be further studied. The subsidence wetlands are still expanding, and if managed effectively, may provide important complementary habitats for a wide array of waterbird species, particularly for those migrating along the East Asian–Australasian Flyway. Our study provides key baseline data regarding the waterbird communities and may help with the designing of effective management and conservation plans.

SummaryAnthropogenic conversion of natural wetlands into artificial wetland habitats has produced complex wetland landscapes worldwide. In this study we investigated the responses of migratory and wintering waterbirds to five artificial wetland habitats (aquaculture ponds, paddyfields, irrigation canals, open water reservoirs and saltpans) within a novel natural-artificial wetland landscape, Yellow River Delta (YRD), eastern China from October 2007 to May 2008. The results showed that almost all bird community indicators in the YRD natural wetlands were higher than those in adjacent artificial wetlands. Across the landscape, natural wetlands remained most important for all waterbird guilds, and more than 90% of waterbird populations were dependent on these habitats. Artificial wetlands mainly provided a secondary role, supporting about 70% of waterbird species (including six species that reached 1% of their global or biogeographical flyway populations), but with distinctive functional capacity for specific waterbird guilds in different artificial wetlands. The conservation value of artificial wetlands is often ephemeral, mainly during autumn, for specific migratory waterbirds and complements that of remaining areas of natural wetlands. Therefore, the utilisation patterns of artificial wetlands are highly temporal and the majority of species are dependent on areas of natural wetland. A comprehensive study of the inter-seasonal and inter-annual variations in these different habitats and dependence by the various guilds in the YRD is required to enable the true value of these habitats to be understood. We suggest that the conservation of artificial wetlands should not be at the expense of natural wetlands, which should remain the priority for wetland landscape management. Management to maintain the existing artificial wetlands for migrating and wintering water birds should target habitat features that are absent or limited in natural wetlands thus increasing the carrying capacity of the YRD landscape.

Compared to external loads from tributaries and sediment recycling, the role of waterbirds as phosphorus (P) sources in estuaries is overlooked. We performed monthly ship-based surveys of waterbird abundance in the Lithuanian part of the Curonian Lagoon, calculated their potential P excretion, and compared its relevance to the riverine inputs. Phosphorus excretion rates for the censused species were assessed accounting for variations of body weights, daily feces production and their P content, and assigning species to different feeding and nutrient cycling guilds. During the study period (March–November 2018), 32 waterbird species were censused, varying in abundance from ~18,000–32,000 (October–November) to ~30,000–48,000 individuals (June–September). The estimated avian P loads during the whole study period varied between 3.6 and 25 tons, corresponding to an area load between 8.7 and 60.7 mg P m−2. Waterbird release of reactive P to the system represented a variable but not negligible fraction (1%–12%) of total external P loads, peaking in June–September and coinciding with cyanobacterial blooms. This study is the first in the Baltic Sea region suggesting that waterbirds are potentially important P sources to phytoplankton in large estuaries, in particular, during low discharge periods.

SummaryMany migratory waterbird populations are in decline and loss of natural wetlands is one of the main causes. However, some species may respond positively to artificial wetland recreation. In Extremadura (south-west Europe), several large reservoirs were created for irrigation since the 1960s and some comparatively small reservoirs were built from the late 1990s onwards close to rice fields. Here we analyse the abundance of wintering dabbling ducks (Anas spp.) in Extremadura before (1991–1994) and after (2007–2010) the creation of these new reservoirs in order to address the current importance of the area for this guild within the East Atlantic Flyway (EAF). A mean of 25,277 dabbling ducks wintered in the study area during 1991–1994, increasing to 46,163 individuals during 2007–2010. After controlling for environmental variables, Northern Pintail Anas acuta, Common Teal A. crecca and Northern Shoveler A. clypeata experienced significant increases in the area between both periods, and only Eurasian Wigeon A. penelope suffered a significant decrease. Mallard A. platyrhynchos and Gadwall A. strepera populations did not show any significant trend. The large older reservoirs experienced overall population decreases between the two periods, with four new reservoirs holding more than 35,000 wintering dabbling ducks. Our results reflect an overall improvement in habitat conditions, driven by the creation of reservoirs near to rice fields that could have resulted in a partial redistribution of wintering dabbling ducks in the EAF. The area emerges as one of the most important wintering sites for dabbling ducks in southern Europe, regularly exceeding two of the Ramsar Convention criteria for the conservation of several populations. The protection of these new reservoirs by legal mechanisms would guarantee the existence of a large functional wetland area, which could also mitigate the loss of natural wetlands for populations using the EAF.

2007/2008
L’obiettivo di questa tesi è valutare l’influenza di vari fattori biotici e abiotici che possono influenzare l’abbondanza degli uccelli acquatici nella laguna di Grado e Marano. La laguna di Grado e Marano è situata nel NE del mare Adriatico e ha un’estensione approssimativa di 160 km2. Il passo introduttivo nell’implementazione della struttura del progetto è stato individuare un sistema innovativo per la raccolta, la standardizzazione e l’archiviazione dei dati ornitologici. Immagini satellitari ASTER sono state utilizzate per classificare differenti tipi di habitat, incluse le praterie di fanerogame. Nel Sistema Informativo Geografico sono state incluse quattro variabili abiotiche (azoto e fosforo totale, salinità e tessitura del sedimento) e tre fattori biotici (comunità bentonica, praterie di fanerogame e l’abbondanza degli uccelli acquatici presenti (Mean values: December 2006, January and February 2007), raggruppati in unita funzionali o guilds). Una griglia UTM con celle di grandezza 1km x 1km (Operational Geographic Units, OGU), è stata sovrapposta all’intera laguna. Per definire le unità ecologiche sono state applicate la classificazione gerarchica e l’analisi delle componenti principali. Da ultimo è stata usata l’analisi di corrispondenza per esaminare la relazione tra uccelli acquatici raggruppati in guilds e le unità ecologiche. L’integrazione dei metodi standard di censimento con i database relazionali per archiviare e analizzare i dati ornitologici, con le tecniche di telerilevamento e di GIS e con i metodi di analisi multivariata, rappresenta un set di strumenti efficienti e potenti per il monitoraggio integrato della laguna. Il soddisfacente risultato ottenuto si potrebbe applicare per ottenere un miglioramento della struttura gestionale di numerose zone umide dell’Adriatico. The purpose of this thesis is to estimate the influence of several biotic and abiotic factors on the abundance of waterbirds in the Grado-Marano Lagoon. The Grado-Marano Lagoon is situated in the Northeast of the Adriatic Sea with an extension of approximately 160 km2. Design of an innovative system for ornithological data gathering, standardisation and storage has been an initial step in the whole project structure. Waterbirds census was carried out by periodically monitoring the bird population over a two-year period (July 2006- July 2008). The present research is making use of the integrated waterbirds census database December 2006 - February 2007 (Daylight Time Counts completed by Aerial Surveys). Terrestrial and aerial survey methods allowed us to describe bird density and habitat use. An Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite images were utilized to classify different types of morphologies and habitat, including sea grass meadows. Four abiotic factors (total nitrogen, total phosphorous, salinity and sediment texture) and three biotic factors (benthic community, sea grass meadows and waterbird guild abundance) were integrated into a GIS. The flexibility of the procedure proposed in this PhD research depends on the concept of the Operational Geographic Unit (OGU) as a useful tool to integrate in a GIS georeferenced multisource data A regular UTM grid of square cells (OGU), 1km × 1km, was superimposed on the entire lagoon. Using the Hierarchical Cluster Analysis technique it was possible to delineate ecological units (clusters of OGUs) and Principal Component Analysis was used to reduce the dimensionality of the factors considered. Subsequently, Correspondence Analysis (CA) was used to examine the relationship between waterbird guild abundance and ecological units. The results obtained from this study show that sea grass meadows represent a fundamental trophic resource for aquatic birdlife in the lagoon. It is therefore indispensable to assess the distribution of phanerogam meadows and to identify the principal ecological parameters. In this context, GIS techniques allow us to integrate significant amounts of environmental data and multivariate analysis helps us to reduce the dimensionality of the data set. The integration of standard waterbirds census methods, relational databases for the ornithological data storing and analysis, remote sensing techniques, GIS technologies and multivariate statistical methods provides us with a set of powerful and efficient tool for lagoon integrated monitoring. It demonstrates the promising potentials in reforming the management frameworks of the numerous coastal wetlands in the Adriatic.
XXI Ciclo
1979