Red-crested Pochard Netta Rufina Research Articles

Changes in the adult sex ratio of six duck species breeding populations over two decades

Despite all efforts, long-term changes in the adult sex ratios of breeding duck populations are still unclear; this uncertainty is especially true for male-bias populations, which are often under the scrutiny of researchers lacking convenient results for the active protection of endangered species. Species with male-bias populations are usually strongly affected by a decline in population size that leads to a higher extinction risk. In this study, we examined our long-term data of the abundance of breeding populations in six duck species (Mallard Anas platyrhynchos, Gadwall Mareca strepera, Red-crested Pochard Netta rufina, Common Pochard Aythya ferina, Tufted Duck Aythya fuligula, and Common Goldeneye Bucephala clangula) from fishponds in South Bohemia, Czechia, between 2004 and 2022. This evidence was used to assess long-term changes in the adult sex ratio in these breeding populations and investigate the possible effects of the NAO index (North Atlantic Oscillation index) on them, indicating climate conditions in winter. We determined a long-term decrease of the proportion of females in the breeding season in two of the six examined species: Common Pochard and Red-crested Pochard, which is driven by the long-term increase in the number of males in contrast to the decreasing or stable number of females likely caused by different migration behaviours between females and males. In the case of Common Pochard, in breeding populations, we estimated 60–65% of males in the early 2000s rising to 75–80% in the early 2020s. However, we establish no significant effects linked to climate conditions of the previous winter in these species as a crucial cause of the changes of the proportion of females in the breeding population.

New Data on the Staging and Winter Behavior of the Red-Crested Pochard Netta rufina in Lake of Birds (North-Eastern Algeria)

New Data on the Staging and Winter Behavior of the Red-Crested Pochard Netta rufina in Lake of Birds (North-Eastern Algeria)

Interactions between stoneworts (Charales) and waterbirds.

Stoneworts (Charales) are green algae that represent an important food resource for many waterbird species in Europe and elsewhere. Browsing avian herbivores (e.g. swan, goose, duck and coot species) consume Charales plant vegetative parts, by head-dipping, up-ending or diving. A lower fibre content and longer growing season may make Charales as attractive to such herbivores as sympatric submerged higher plant species in some circumstances. Charales respond to environmental stress (e.g. drought) by producing abundant diaspores, in the form of oospores (sexual) and bulbils (asexual), both rich in starch, generating abundant food for waterbirds at critical stages in their annual migratory cycles. Waterbirds feed on these by diving (e.g. common pochard Aythya ferina and red-crested pochard Netta rufina) or by filtering from the water column (e.g. dabbling duck species), ensuring dispersal of sexually produced and vegetative diaspores locally (because of predator swamping) and remotely (through endo- and ectozoochorous dispersal by long-distance migratory waterbirds). Greater invertebrate density and diversity associated with Charales canopies enhances their attractiveness over other submerged macrophyte beds to diving predators [e.g. tufted duck Aythya fuligula, common pochard and Eurasian coot Fulica atra (hereafter coot)]. Fish fry preying on these invertebrates use such vegetation as predator cover, in turn providing prey for avian piscivores such as grebes and cormorants. Abundant Charales contribute to maintaining a transparent water column due to canopy density, nutrient effects, dampening of sedimentation/remobilisation of suspended matter and nutrients and allelopathic effects on other plants (especially phytoplankton). Shallow, relatively eutrophic waters can flip between clear-water high-biodiversity (where Charales thrive) and turbid species-poor depauperate stable states (lacking Charales). Shifts between turbid conditions and rich submerged Charales beds have profound elevating effects on aquatic diversity, to which waterbirds show rapid aggregative responses, making them ideal indicator species of ecological change; in the case of Charales specialists (such as red-crested and common pochard), indicators of the presence and abundance of these plants. Large-bodied colonial nesting birds (e.g. cormorants, gulls, heron and egrets) aggregating along lake shores contribute high N and P loadings to water bodies sensitive to such external and internal inputs and can cause local eutrophication and potential loss of Charales. Despite variation from complete seasonal removal of Charales biomass to undetectable grazing effects by herbivorous birds, evidence suggests little effect of avian grazing on biomass accumulation or the stability of community composition (under otherwise stable conditions), but we urge more research on this under-researched topic. We also lack investigations of the relative foraging profitability of different Charales organs to waterbirds and the degree of viability of gyrogonites (fertilised and calcified oospores), vegetative bulbils and plant fragments after passage through the guts of waterbirds. We especially need to understand better how much the carbonate armour of these organs affects their viability/dispersal via waterbirds and urge more research on these neglected plants and their relationships and interactions with other organisms in the aquatic biota.

New Data on the Staging and Winter Behavior of the Red-Crested Pochard Netta rufina in the Lac des Oiseaux (North-Eastern Algeria)

New Data on the Staging and Winter Behavior of the Red-Crested Pochard Netta rufina in the Lac des Oiseaux (North-Eastern Algeria)

Status of water birds in Haripura-Baur Reservoir, western Terai-Arc landscape, Uttarakhand, India

We surveyed water birds in Haripura-Baur Reservoir using total count method between 2013 and 2015. A total of 65 species were recorded representing eight orders and 14 families. Numerically Anatidae was the dominant family followed by Ardeidae and Scolopacidae. Common Coot Fulica atra, Red-crested Pochard Netta rufina, Common Pochard Aythya ferina, Gadwall Anas strepera, and Tufted Pochard Aythya fuligula were dominant species in the reservoir. The Shannon diversity of water birds was more or less consistent over the years and ranged between 2.56 (2013–14) and 2.23 (2015–16). The reservoir supports water birds having declining population trends globally (41% of species), including three Vulnerable (Asian Woollyneck Ciconia episcopus, Lesser Adjutant Leptoptilos javanicus, and Sarus Crane Grus antigone and four Near Threatened species (Oriental Darter Anhinga melanogaster, Painted Stork Mycteria leucocephala, Black-necked Stork Ephippiorhynchus asiaticus, and River Lapwing Vanellus duvaucelii). Bird species belong to four feeding guilds with the domination of the carnivore group. The current information is expected to serve as preliminary database of water birds for further research and monitoring.

Diving duck census efficiency based on monitoring of individually marked females: the influence of breeding stage and timing of census

ABSTRACTCapsule: Observations of individually marked females of three diving duck species showed that the stage of breeding season and census month most affected their resighting probability in the breeding season.Aims: To evaluate the efficiency of a diving duck census in the breeding season based on an analysis of the resighting probability of individually marked female ducks.Methods: We used monitoring data from 2004 to 2015 of individually marked females of Common Pochard Aythya ferina, Tufted Duck Aythya fuligula and Red-crested Pochard Netta rufina in South Bohemia, Czech Republic. Using a model selection approach, the resighting probabilities of females were modelled incorporating covariate parameters, such as stage of breeding, census month, year, numbers of counted individuals, individual species, water surface area and proportion of emergent vegetation.Results: We demonstrated the significant effect of the stage of breeding, year and census month on the resighting probability of females, while the number of individuals, water surface area and proportion of emergent vegetation did not contribute to the best models. Moreover, the three investigated species with different local population sizes did not differ in resighting probabilities. The incubation period of the females (i.e. June) corresponded to the lowest detection probability in the study area.Conclusions: Our approach of using individually marked females contributed to modelling to show census accuracy for diving ducks was substantially enhanced by avoiding counting females during the incubation period. Ultimately, these findings are crucial to increase the accuracy of their breeding population size estimation.

Density-dependent regulation of breeding success in the Red-crested Pochard Netta rufina

ABSTRACTCapsule: Numbers of breeding Red-crested Pochard Netta rufina in the Czech Republic were positively correlated with reproductive success in the previous year, yet annual productivity, declined with increasing numbers of females at the beginning of the breeding season, suggesting local limiting factors on this population.Aims: To test the hypothesis that long-term increases in numbers of a breeding population of Red-crested Pochard Netta rufina can be explained by the productivity (numbers of ducklings fledged) in the previous year. We also test for the potential adverse effect of population size on population productivity in the current year.Methods: Data from 2004 to 2016 from South Bohemia, Czech Republic, were analysed using TRends and Indices for Monitoring Data software to investigate changes in numbers of adults, numbers of females at the start of the breeding season and number of broods produced.Results: There was a significant increase in the numbers of adults and females at the beginning of each breeding season. Numbers of adults in May positively correlated with productivity (numbers of ducklings fledged) in the previous breeding season, but relative productivity (broods per adult female) in the current year was negatively correlated with females abundance at the beginning of the breeding season.Conclusions: The study identifies density-dependent regulation as a factor in the population productivity of Red-crested Pochards using intensively managed fishponds as a breeding ground.

The effects of cessation of fish farming on duck breeding in French fishpond systems

Fishponds are man-made aquatic systems subjected to more or less active management by fish farmers. They also are an important habitat category for waterbirds. In this study, we attempted to assess the consequences for duck breeding of fish farming interruption in a typical French fishpond region, the Forez, where fish production has declined strongly since the 1990s. Duck pair density, a brood: pair ratio and mean brood size were studied in two successive periods, 2010–2012 and 2013–2015, in 19 ponds abandoned for fish farming between 2008 and 2010, and in 34 ponds still stocked with fish among which 17 were harvested every 2 or 3 years and 17 harvested annually. Between the two study periods, a decrease in abandoned ponds was observed in diving duck (Aythya species) and red-crested pochard Netta rufina pair density and for dabbling duck (Anas species) and red-crested pochard brood: pair ratio. A possible explanation is that fish influenced the nutrient level within the aquatic ecosystem through bioresuspension of phosphorus when stirring the sediment for feeding and through nitrogen production by excretions. Decreased brood sizes in ponds still used for traditional fish farming are suggested to be the result of density-dependent predation rates.

Important Bird Areas in Macedonia: Sites of Global and European Importance

Important Bird Areas in Macedonia: Sites of Global and European Importance

Changes in Behavioral Time Allocation of Waterbirds in Wing-Molt at Lake Constance

The reduced mobility of flightless waterbirds during wing-feather molt should influence time allocation during the day, but time-budget studies are lacking in most species. Here, time budgets of flightless and fully-winged individuals at Lake Constance, Central Europe, were compared for five waterbird species with different feeding ecology and varying sensitivity to disturbances or predation pressure. Significant differences in diurnal activity budgets of flightless and fully-winged birds were observed in all five species. Different behaviors were responsible for the observed differences. Flightless Mute Swans Cygnus olor spent more time feeding while decreasing locomotory activity. Red-crested Pochard Netta rufina also increased feeding, but, in addition, had increased locomotory activity while resting less. In contrast, flightless individuals of both Gadwall Anas strepera and Tufted Ducks Aythya fuligula spent less time foraging, while there was no such change in Eurasian Coot Fulica atra. More consistent patterns were observed in vigilance behavior, which increased in three of the five species. Comfort activities, such as preening, increased in two species, and were unchanged in the remaining three. Social interactions, which constituted only a small part of the daily budget, only changed in Gadwall. The present data suggest that the five waterbird species meet the increased energy demands during molt by either one or a combination of behavioral adaptations, i.e. different strategies, such as higher nutrient intake (e.g. Mute Swan, Red-crested Pochard), lower energy consumption by reducing the locomotory component (e.g. Mute Swan, Tufted Duck) or a breakdown of energy reserves deposited prior to the molting period resulting in more time spent resting (e.g. Gadwall). Also, increased resting times during the day may indicate nocturnal feeding, which needs to be examined in more detail.

Compared distribution within a disturbed fishpond ecosystem of breeding ducks and bird species indicators of habitat quality

The distribution of breeding ducks versus three other bird species (Mute Swan Cygnus olor, Black-headed Gull Larus ridibundus and Purple Heron Ardea purpurea) among waterbodies was investigated in the Dombes area, Eastern France, where breeding duck populations have undergone a severe decline following a large-scale transformation of meadow habitat into cropland. Higher Pochard Aythyaferina, Tufted Duck Aythyafuligula, Red-crested Pochard Netta rufina and Gadwall Anas strepera pair densities were recorded in fishponds where Black-headed Gulls were nesting. In these ponds however, nesting success (assessed by the number of broods divided by the number of pairs) was not significantly higher. Similarly, Pochard pair density was higher in ponds with a Purple Heron colony, but brood densities were not. We hypothesise that, in the study region, clutch concentration in the most attractive areas could compensate for the anti-predation effect of gull colonies or overwater nesting in shore vegetation. We could not confirm the expected negative impact of Mute Swan aggressive behaviour on duck distribution. Even though Mallard Anas platyrhynchos pair density was lower in ponds with breeding swans, we did not observe difference for Mallard broods. Moreover, Red-crested Pochard pair density and nesting success were higher in ponds where swans were breeding, probably as a consequence of shared habitat preferences.

Is the Red-crested Pochard Netta rufina really Endangered in France ?

Is the Red-crested Pochard Netta rufina really Endangered in France ?

Winter distribution and population change of Red-crested Pochard Netta rufina in southwestern and central Europe

Under the African-Eurasian Waterbird Agreement (AEWA) of the Convention on Migratory Animals (Bonn Convention), the Red-crested Pochard Netta rufina has a high conservation priority in Europe. This is particularly the case for the southwest/central European flyway population, which is considerably smaller than the southeast European and Asian ones. Data from the International Waterbird Census from 1967 to 1994 indicate that the flyway population has remained at a similar level between the mid-1980s and mid- 1990s, but is likely to be smaller than it was in the 1970s. Population size in January is estimated to be between 25 000 and 30 000 individuals. In winter, the Red-crested Pochard is concentrated at a small number of sites. In the period 1985–94, 75% of the population were observed at the six main sites: Laguna de Gallocanta, Albufera de Valencia, Delta del Ebro, Marismas del Guadalquivir (all in Spain), Camargue (France) and Lac de Neuchâtel (Switzerland). In January, 39 sites held ≥1% of the population at least once between 1975 and 1994. The Red-crested Pochard has recently shown a marked change in its winter distribution, and two patterns emerged: (1) a shift from the western Mediterranean to the region north of the Alps; and (2) the use of a greater number of sites.

Parasitic Laying in Red-Crested Pochard Netta rufina Nests

Parasitic Laying in Red-Crested Pochard Netta rufina Nests

La valeur ornithologique des zones humides de l'est Algerien

In the environs of the town of El Kala in northeast Algeria there are some extensive wetlands of great ornithological, and probably also other biological, importance. The most important are ‘Lake’ Tonga, a marsh of about 2700 ha with much Scirpus lacustris; Lake Oubeïra, a freshwater lake of about 2200 ha; Lake Mellah, where fresh water from brooks and sea water meet, of about 800 ha; Garaet el Mekhada, a Scirpus maritimus marsh of about 5600 ha and swamp forests, which could not be investigated. Many species of waterfowl were seen in the second half of May, 1976. From these and some other observations probable breeding may be derived in many cases. Important species in the region are: squacco heron Ardeola ralloides (about 100 seen), cattle egret Bubulcus ibis (about 2000 seen), little egret Egretta garzetta (about 65 seen), grey heron Ardea cinerea (rare), purple heron Ardea purpurea (about 60 seen, possibly far more present), little bittern Ixobrychus minutus, bittern Butaurus stellaris and night heron Nycticorax nycticorax. Beside herons, the following species were seen: ferruginous duck Aythya nyroca (about 100 seen, probably far more numerous and hidden by the vegetation), white-headed duck Oxyura leucocephala (some 50 seen, probably present in greater numbers), marbled teal Anas angustirostris, purple gallinule Porphyrio porphyrio (common in Tonga). Interesting birds of prey in the region were griffon vulture Gyps fulvus (up to 30), marsh harrier Circus aeruginosus (rather numerous in Tonga), tawny eagle Aquila rapax (probably breeding on one place) and Eleonora's falcon Falco eleonorae (up to 5). As to probable breeding birds, Tonga has the greatest density of species and individuals, but other wetlands also have important aspects. Probably the most important lake for breeding birds, Fetzara (near Annaba), was drained in 1937. Marbled teal, ferruginous duck and purple gallinule were very common there, and white-headed duck, purple heron, squacco heron, night heron, little egret, spoonbill Platalea leucorodia, glossy ibis Plegadis falcinellus, grey-lag goose Anser anser, red-crested pochard Netta rufina and gadwall Anas strepera used to breed. A brief review is given of wintering waterfowl, mainly based on counts by different observers in the period 1971–1979. Large numbers of waterfowl have been seen in Lake Oubeïra; up to 5000 pintail Anas acuta, up to 14000 wigeon Anas penelope, up to 27000 pochard Aythya ferina, up to 9000 tufted duck Aythya fuligula and up to 32000 coot Fulica atra, up to 850 black-necked grebe Podiceps nigricollis and up to 2300 little grebe Tachybaptus ruficollis. In Lake Mellah up to 9000 pochard have been seen, up to 12000 tufted duck, and up to 35000 coot. In Garaet al Mekhada up to 25000 wigeon, up to 5000 coot and up to 8000 grey-lag geese have been seen. It seems quite possible that the 95000 wigeon seen by Smart in the artificial lake of the Barrage de la Cheffia in 1974 fed in Mekhada. An insight of waterfowl averages during the different counts can be obtained from the reports, mentioned in the references. All large wetlands mentioned have a high, actual or potential, ecological value. Each of them deserves protection and, from the ecological viewpoint, Fetzara merits inundation. Protection should be aimed at the preservation of the special character of each of the wetlands and of their mutual relationship for birds. The region is the most important in Algeria for wintering duck and coot (an average of 93000 from 1974–1978) and probably also for breeding waterfowl (especially Tonga) in spite of the high quality of La Macta in West Algeria. For the preservation of this diversity, several factors are essential, e.g., water level, water quality, absence of exotic elements in the water fauna and a relatively low shooting pressure (with little disturbance). It is important to prevent drainage of the lakes and of their surroundings, afforestation of the adjacent land, deforestration and erosion in the catchment areas, introduction of exotic fish species—and it is important to introduce good rules concerning shooting. This complex of wetlands is part and parcel of an extensive area of high biological interest, of which the marine habitats and large semi-natural forests are also remarkable. It is to be hoped that this entity will be efficiently protected in the framework of the National Park of El Kala Project.

Need for conservation of creeks in North-East Flanders, Belgium

In the environs of the town of El Kala in northeast Algeria there are some extensive wetlands of great ornithological, and probably also other biological, importance. The most important are ‘Lake’ Tonga, a marsh of about 2700 ha with much Scirpus lacustris; Lake Oubeïra, a freshwater lake of about 2200 ha; Lake Mellah, where fresh water from brooks and sea water meet, of about 800 ha; Garaet el Mekhada, a Scirpus maritimus marsh of about 5600 ha and swamp forests, which could not be investigated.Many species of waterfowl were seen in the second half of May, 1976. From these and some other observations probable breeding may be derived in many cases. Important species in the region are: squacco heron Ardeola ralloides (about 100 seen), cattle egret Bubulcus ibis (about 2000 seen), little egret Egretta garzetta (about 65 seen), grey heron Ardea cinerea (rare), purple heron Ardea purpurea (about 60 seen, possibly far more present), little bittern Ixobrychus minutus, bittern Butaurus stellaris and night heron Nycticorax nycticorax.Beside herons, the following species were seen: ferruginous duck Aythya nyroca (about 100 seen, probably far more numerous and hidden by the vegetation), white-headed duck Oxyura leucocephala (some 50 seen, probably present in greater numbers), marbled teal Anas angustirostris, purple gallinule Porphyrio porphyrio (common in Tonga). Interesting birds of prey in the region were griffon vulture Gyps fulvus (up to 30), marsh harrier Circus aeruginosus (rather numerous in Tonga), tawny eagle Aquila rapax (probably breeding on one place) and Eleonora's falcon Falco eleonorae (up to 5).As to probable breeding birds, Tonga has the greatest density of species and individuals, but other wetlands also have important aspects.Probably the most important lake for breeding birds, Fetzara (near Annaba), was drained in 1937. Marbled teal, ferruginous duck and purple gallinule were very common there, and white-headed duck, purple heron, squacco heron, night heron, little egret, spoonbill Platalea leucorodia, glossy ibis Plegadis falcinellus, grey-lag goose Anser anser, red-crested pochard Netta rufina and gadwall Anas strepera used to breed.A brief review is given of wintering waterfowl, mainly based on counts by different observers in the period 1971–1979. Large numbers of waterfowl have been seen in Lake Oubeïra; up to 5000 pintail Anas acuta, up to 14000 wigeon Anas penelope, up to 27000 pochard Aythya ferina, up to 9000 tufted duck Aythya fuligula and up to 32000 coot Fulica atra, up to 850 black-necked grebe Podiceps nigricollis and up to 2300 little grebe Tachybaptus ruficollis.In Lake Mellah up to 9000 pochard have been seen, up to 12000 tufted duck, and up to 35000 coot.In Garaet al Mekhada up to 25000 wigeon, up to 5000 coot and up to 8000 grey-lag geese have been seen. It seems quite possible that the 95000 wigeon seen by Smart in the artificial lake of the Barrage de la Cheffia in 1974 fed in Mekhada. An insight of waterfowl averages during the different counts can be obtained from the reports, mentioned in the references.All large wetlands mentioned have a high, actual or potential, ecological value. Each of them deserves protection and, from the ecological viewpoint, Fetzara merits inundation. Protection should be aimed at the preservation of the special character of each of the wetlands and of their mutual relationship for birds.The region is the most important in Algeria for wintering duck and coot (an average of 93000 from 1974–1978) and probably also for breeding waterfowl (especially Tonga) in spite of the high quality of La Macta in West Algeria.For the preservation of this diversity, several factors are essential, e.g., water level, water quality, absence of exotic elements in the water fauna and a relatively low shooting pressure (with little disturbance). It is important to prevent drainage of the lakes and of their surroundings, afforestation of the adjacent land, deforestration and erosion in the catchment areas, introduction of exotic fish species—and it is important to introduce good rules concerning shooting.This complex of wetlands is part and parcel of an extensive area of high biological interest, of which the marine habitats and large semi-natural forests are also remarkable.It is to be hoped that this entity will be efficiently protected in the framework of the National Park of El Kala Project.