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Hydrological Management in a Restored Wetland Affects Stopover Ecology of Aquatic Warbler: The Case of La Nava Wetland, Northern Spain
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The Aquatic Warbler (Acrocephalus paludicola) is one of the most threatened migratory passerine birds in the world. The species stops over at both European and African wetlands during its migration. Using data from a long-term ringing program in the restored wetland of La Nava (Spain), we describe several aspects of the species' stopover ecology at this site with special focus on juveniles: (1) timing of migration, (2) population size, (3) fuel reposition rate, (4) stopover duration and (5) site fidelity. We elaborated two Multiple Linear Regressions and a Generalized Linear Model to estimate the determinants of migration phenology, daily fattening rate and abundance of captures in addition to minimum observed stopover duration. Finally, we calculated return rates to estimate stopover site fidelity. We determined that: this stopover site belongs to an Atlantic migration route; juveniles experience delayed migration; and that reduced captures are associated with more restrictive hydrological management. Return rate results suggested that there is stopover site fidelity is low. Our results may indicate that this stopover site serves primarily as a resting place rather than a refuelling habitat for this species.
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... Techniques like phosphate stripping and suction dredging are being considered to restore water quality (Wagstaff et al., 2021). The La Nava Wetland in Spain is being treated to eliminate effluents (Muñoz-Adalia et al., 2015). The government of Japan has set pollution reduction goals following the pollution of Lake Biwa (Kondo et al., 2021). ...
Water quality is affected by increased urbanization as pollutants produced in the urban environment settle and contaminate water, and there is an increase in competition of water among cities, industries, agriculture, etc. The quality and quantity of water are affected by alterations in the microclimate, water dynamics, geomorphology, ecology, and biogeochemistry. As more pavements get created, it becomes increasingly difficult for water to soak into the ground and this causes a decrease in the water table. Impervious structures like streets and roofs when washed with rain deposit excessive pollutants in water bodies. The overall increase in water pollution is a potential health hazard for humans and aquatic life. Hence it is necessary to take adequate measures for addressing the water pollution issue that may potentially arise due to increased urbanization. In this study, we tackle the issue using two approaches. The first approach deals with analyzing the water quality to determine its potability using fifteen different types of machine learning techniques like random forests, decision trees, support vector machines, artificial neural networks, etc. The model has been evaluated using metrics such as precision, recall, accuracy, and F-1 score. The second approach deals with identifying marine litter from beaches in many parts of the world using machine learning algorithms. We also explore the different types of beach environments and the type of litter that is found in different locations using extensive exploratory analysis. Both approaches can be used for ensuring sustainable urban development by reducing water pollution.
... Mist nets catch a bigger range of species than other methods such as cannon netting or whoosh netting, and is principally used for smaller bird groups like passerines but ringers can obtain licenses to ring a whole array of birds from different orders. Mist nets are suitable to deploy near to water and monitoring data can be used to study migratory species or for population studies (Muñoz-Adalia et al. 2015). ...
Freshwater habitats are vitally important for vertebrate diversity and ecosystem service provision. These habitats are diverse in scale and type, ranging from vast wetlands and tropical flooded forests to small streams and ponds, but are all equally important to the diverse range of vertebrates they support. The loss and degradation of freshwater habitats globally, largely driven by agricultural intensification, land-use change and deforestation, threatens vertebrates and the continued functioning of freshwater ecosystems. Well-informed, evidence-based conservation is reliant on suitably designed surveys capable of detecting population changes in target species. Due to the diversity and complexity of freshwater habitats and their associated vertebrate taxa a comprehensive review of all methods for all species is beyond the scope of this chapter. However, here we outline key considerations and methods for surveying vertebrates in freshwater systems and provide signposts to relevant case studies and resources to help plan successful monitoring programmes for freshwater vertebrates.
... Valcavado stream is surrounded by areas covered with herbaceous and helophytic vegetation, temporarily flooded during summer (Miguélez et al. 2009). La Nava is a restored wetland classified as an important special protection area (Natura 2000;Muñoz-Adalia et al. 2015). All birds captured were marked individually with a metal ring, measured (wing length) and aged according to plumage. ...
Mercury (Hg) contamination is considered a global concern for humans and wildlife, and although the number of studies dealing with that issue continues to increase, some taxonomic groups such as small passerine birds are largely understudied. In this paper, concentration of mercury in the aquatic warbler (Acrocephalus paludicola) feathers, a globally threatened passerine species, was examined. The concentration differences between two ages and sexes were investigated. The comparison of feathers taken on autumn migrants of two age categories act as a comparison of the species’ exposure within the two different areas (European breeding or African wintering grounds). The average Hg concentration for all sampled individuals [2.32 μg/g dw (range 0.38–12.76)] is relatively high, compared with values found in other passerine species. An age difference was found, with first-year individuals displaying higher mercury concentrations than adults. This indicates that birds are exposed to mercury pollution during the breeding season, i.e., in the continental floodplains of eastern Europe. The average Hg concentration in feathers grown on the breeding grounds was 3.88 ± 2.59 μg/g dw, closer to the critical value of 5 μg/g dw, which is considered to impair the health of individuals. The findings suggest that mercury pollution may constitute a threat so far neglected for the endangered aquatic warbler.
Selection of timing to match optimal environments is crucial for migrants that breed at high latitudes where there is a narrow time window suitable for breeding. However, birds generally depart from non-breeding grounds in a broad time window. How birds adjust their migration schedule to match optimal timing of arrival at breeding grounds is largely unexplored. We radio-tracked Great Knots Calidris tenuirostris at stopping sites in the southern and northern Yellow Sea during the entire stopping periods to determine their time schedules during northward migration. Great Knots stayed for 40.7 +/- A 9.2 days (n = 11) in the whole Yellow Sea, with the early arrivals having a longer length of stay than the late arrivals. There was no significant difference in the length of stay between birds that arrived on various dates in the southern Yellow Sea, while the late arrivals spent less time during flights from the southern to the northern Yellow Sea, and stayed for a shorter time than the early arrivals in the northern Yellow Sea. We estimated that the later arrivals can still moult into full breeding plumage and deposit enough fuel for a flight to the breeding grounds before departure. We propose that early and latter migration are the two ends of migratory schedule, with the former adapting to unpredictable and rigorous environments and the latter to stable and favourable environments en route. Stopping sites play an important role for birds to adjust their migration schedule to meet optimal timing of arrival at migratory destination.
The Afro-Palearctic migrant Aquatic Warbler Acrocephalus paludicola has been known as an abundant breeding bird in eastern Europe until the 20th century, after which it began to decrease in a number of countries due to several threats (essentially anthropogenic) changing the ecological functioning of its key sites (de By 1990, Flade & Lachmann 2008, Tanneberger et al 2008). The drastic decrease of the global population in the last decades has led to a growing awareness of its status and of the importance to develop strategies for the conservation of the species. Hence, Aquatic Warbler was classified as 'threatened' in the IUCN Red List, before becoming 'vulnerable' in 1994 and attributed to the SPEC 1 category, ie, in the category of 'species of global conservation concern' (BirdLife International 2004). Those statuses make the species the most threatened migratory songbird in Europe. In this context, the Aquatic Warbler Conservation Team (AWCT) has been founded in Germany in 1998, under the auspice of BirdLife International, coordinating , implementing , gathering data and making available all studies and information about the species. Moreover, an international Memorandum of Under standing (MoU) concerning Conservation Measures for Aquatic Warbler has been concluded in 2003 under the auspice of the Bonn convention (Convention on Migratory Species 2003). It constituted a collective working basis for all the signatory countries , currently 16 (Conven tion on Migratory Species 2012). In 2008, an International Species Action Plan for Aquatic Warbler was attached to the MoU. It was commissioned by the European Commission and prepared by BirdLife International (Flade & Lachmann 2008). This plan summarized the knowledge on Aquatic Warbler and fixed targets about the global population such as its stabilization and in the longer term, its increase. As Aquatic Warbler is a trans-Saharan migrant, its conservation involves all countries that at any time host the species during breeding, migration and wintering periods. Thus, on the base of studies performed to identify wintering grounds (Schäffer et al 2006) and migration routes (Julliard et al 2006), the signatories of the MoU and the International Species Action Plan have set up studies in all 22 range states to improve the conservation status of Aquatic War bler (Convention on Migratory Species 2010). Breeding population size The current breeding population of Aquatic Warbler is estimated at 11 000-16 000 singing males, corresponding with 22 000-32 000 adult individuals or 33 000-48 000 adults and juveniles (BirdLife International 2012). Seven countries hold breeders (Belarus, Germany, Hungary, Lithu-ania, Poland, Ukraine and, irregularly, Russia) in less than 40 sites together covering only c 1000 km². Moreover, almost 80% of the global population is concentrated in only four sites, essentially in Belarus, Poland and Ukraine (Flade & Lachmann 2008). Four biogeographic populations are known but two of them are likely to disappear within a short period of time because of their very small size and their high geographic and/or genetic isolation: the genetically isolated Pomeranian population (northwestern Polish and German population of c 80 males) and the western Siberian (Russian) population, isolated from the core population by c 4000 km (Flade & Lachmann 2008, Gießing 2002). Aquatic Warbler is an extreme habitat specialist. It occurs in open wetlands, like fen mires, characterized by meso trophic to poor eutrophic level, without any shrub and too much reed vegetation (
The Isthmus of Tehuantepec in southern M6xico seems to cause a concentration of Nearctic-Neotropic mi • ;rant landbirds during migration. Despite its possible importance as an area for fat deposition, almost nothing is known about how this area is used by migrants. Of 11 small passefine species examined, 6 showed significant diurnal increases in body condition in relation to time of capture. All six showed gains suggesting low to moderate levels of fat deposition, concordant with the concept of the Isthmus as an important source of stopover resources. The area is not used in the same manner by all of these common species, however. The migrants at this site in autumn probably have not arrived via a long-distance, trans-Gulf migration. Comparison with data from other sources suggests that the energetic costs of molt are important at northerly stopover sites, and that modifications are needed in our concepts of Middle American migration routes. Received 8 February 1994, accepted I April 1994.
The Aquatic Warbler Acrocephalus paludicola in Txingudi (N Spain): notes on certain features of the autumn migration period The aim of this paper is to analyze the migratory behaviour of the Aquatic Warbler in Txingudi (N Spain). We considered data obtained over a period of three years (2007–2009) from daily ringing during post-nuptial passage. We captured a total of 29 birds in the months of August (24) and September (5), thus obtaining an Acrola index of 0.924% (percentage of Aquatic Warblers out of the total number of Acrocephalus sps. trapped). This rate is lower than in NW France (> 1 to 3.5%), one of the main areas for fat replenishment and rest on this species' migratory route, similar to that found in SW France (0.8%), but higher than the average for Portugal (0.14%). Altogether, 76% of the captured birds were juveniles. Body mass and fat loads were lower than the values recorded in NW Spain (mouth of the river Miño), but similar to other nearby areas in N Spain (Salburua). In one year four birds were recaptured, giving an estimated average stopover time of 5 days and body mass gain rate of 0.1 g / day (excluding a bird that lost 1 g in a single day). Thus, despite its suboptimal habitats, the length of stay and the body mass gain of Aquatic Warblers in Txingudi did not differ greatly from other wetlands such as La Nava in Palencia, where optimal habitats exist. Txingudi, therefore, would seem to be relevant as a stopover and fat replenishment site for the Aquatic Warbler in the Iberian Peninsula.
Relatively little attention has been paid to sex differences in the migration of birds in autumn. We studied the autumn migration strategy of molecularly sexed males and females in the globally threatened aquatic warbler Acrocephalus paludicola. We captured 176 birds at a stopover site in the Loire estuary at Donges, France. The median date for the passage of adults was 8 days earlier in males than females, although the timing of migration in first-year males and females was similar. This indicates that males, who are without parental duties, can start their migration earlier than females and first-year birds. Adults were significantly heavier than immature birds but did not have higher fat scores. In both age categories, more males (two to three times more) were captured. However, various factors (including tape-luring) can affect observed sex ratio.
Water level and water surface area fluctuations are important factors determining abundance of bird populations and bird assemblages structure in a wetland habitat. The water level and water surface area of the Marsh Tömörd (West Hungary) changed drastically between 1998 and 2008, and the marsh dried out because of scarce rainfall in 2000 and 2001. A habitat restoration in winter 2001 repaired the waterholding capacity of the marsh. We analyzed changes in parameters of bird assemblages in investigated wetland area in relation of environmental factors. We used full redundancy analysis (RDA) on number of caugth migratory birds per year, species richness, diversity and evenness of bird assemblages to examine correlations among water level, water surface area and vegetation core. Species like water rail, common snipe, river warbler, Savi’s warbler, great reed warbler, reed warbler, marsh warbler, sedge warbler, reed bunting showed high and positive linear correlations with the water level and water surface area in the postbreeding period. Some wetland species, sedge warbler, Savi’s warbler and reed bunting as well as total number of caugth birds per year and total numbers of caugth species per year were clearly associated with thick marsh vegetation. According to our results the bird species composition of the wetland might have returned to the prerestoration levels and surface areas.
The Aquatic Warbler Acrocephalus paludicola is a globally threatened songbird and its decline is related to habitat loss. Accordingly, most studies dealing with the stopover ecology of this species have been chiefly focused on the habitat use and the availability of suitable habitats along its route of migration. In contrast, much less attention has been paid to other environmental causes potentially explaining the use of stopover sites. Our aim here was to investigate whether the Aquatic Warbler at an apparently suboptimal stopover site with small area of suitable habitats stops over only during adverse weather conditions. We used data obtained at a suboptimal (Jaizubia marshland, northern Iberia) and another optimal (Villefranque, southwestern France) stopover sites during the autumn migration over four seasons (2007-2010). The Aquatic Warbler tended to stop over at Jaizubia in days with rain, a fact that was not so evident at Villefranque, supporting the hypothesis that they used the suboptimal site only, or mostly, when adverse weather conditions forced them to land. In contrast, the optimal habitat was used independently of weather conditions. To properly identify key stopover localities for the Aquatic Warbler, we should consider the potential influence of adverse weather in occurrence of individuals, especially in small areas without preferred habitat.
The aim of this paper is to analyze the migratory behaviour of the Aquatic Warbler in Txingudi (N Spain). We considered data obtained over a period of three years (2007-2009) from daily ringing during post-nuptial passage. We captured a total of 29 birds in the months of August (24) and September (5), thus obtaining an Acrola index of 0.924% (percentage of Aquatic Warblers out of the total number of Acrocephalus sps. trapped). This rate is lower than in NW France (> 1 to 3.5%), one of the main areas for fat replenishment and rest on this species' migratory route, similar to that found in SW France (0.8%), but higher than the average for Portugal (0.14%). Altogether, 76% of the captured birds were juveniles. Body mass and fat loads were lower than the values recorded in NW Spain (mouth of the river Miño), but similar to other nearby areas in N Spain (Salburua). In one year four birds were recaptured, giving an estimated average stopover time of 5 days and body mass gain rate of 0.1 g/day (excluding a bird that lost 1 g in a single day). Thus, despite its suboptimal habitats, the length of stay and the body mass gain of Aquatic Warblers in Txingudi did not differ greatly from other wetlands such as La Nava in Palencia, where optimal habitats exist. Txingudi, therefore, would seem to be relevant as a stopover and fat replenishment site for the Aquatic Warbler in the Iberian Peninsula.
Science is about discovering new things, about better understanding processes and systems, and generally furthering our knowledge. Deep in science philosophy is the notion of hypotheses and mathematical models to represent these hypotheses. It is partially the quantification of hypotheses that provides the illusive concept of rigor in science. Science is partially an adversarial process; hypotheses battle for primacy aided by observations, data, and models. Science is one of the few human endeavors that is truly progressive. Progress in science is defined as approaching an increased understanding of truth – science evolves in a sense.
Many of the world's lagoons and estuaries, representing the most important habitat for shorebirds, are increasingly degraded, often associated with dramatic declines in shorebirds, particularly in Asia. We investigated effects of hydrology on shorebird communities of two coastal lagoons of a Ramsar site in south-east Sri Lanka. One of the lagoons (Bundala) experienced natural water level fluctuations, while the other (Embilikala) had high stable water levels (>10 cm), maintained by inflows from irrigated agriculture. These inflows dramatically affected composition and abundance of shorebird communities and their prey. Tactile and visual foraging shorebirds were consistently more abundant on Bundala than Embilikala lagoon. Their feeding efficiency was significantly (50%) higher on Bundala, where large (500 gm) benthic prey were more abundant than on Embilikala. Contrastingly, small (60 gm) planktonic prey dominated the hydrologically stable Embilikala lagoon where pelagic foraging shorebird species dominated the shorebird community. On both lagoons, visual and tactile species foraged predominantly in shallow water (1-10 cm). Pelagic shorebirds also foraged in water depths >10 cm but 20% less efficiently than in shallower water. Effective shorebird conservation depends on reducing anthropogenic impacts that detrimentally affect functional processes and habitat value. The detrimental effect of altered hydrology on Embilikala lagoon could be reversed by diverting drainage water. Re-establishing a natural hydroperiod, would increase the productivity of the lagoon for foraging shorebirds. Restoration of shorebird habitat on this Ramsar site could also improve other ecosystem services such as fisheries and tourism. Changes to the hydrology of coastal lagoons elsewhere may be similarly affected.