Red-crested Pochard Research Articles

Submersed macrophytes as a food source for wintering waterbirds at Lake Constance

We investigated the relationship between Charophytes and herbivorous waterbirds in the littoral zone of Lake Constance by quantifying their seasonal dynamics. The waterfowl extensively consumed Charophyte vegetation in shallower areas (<1 m water depth) at the beginning of the winter season, while deeper regions were only used in late winter. By the end of winter, the waterfowl had almost completely depleted the available Charophyte biomass down to a water depth of approximately 2 m (relative to average mean water level (AML)). Enclosure experiments revealed that senescence processes had a negligible influence on Charophytes biomass loss until early February. Coot, Red-crested Pochard and Pochard are the main avian Chara consumers in winter. Despite their great influence on biomass in winter, their influence on subsequent Charophyte regeneration is probably limited in Lake Constance, since Charophytes as typical pioneer species produce innumerable diaspores forming dense Charophyte meadows at a depth of between 1 and 4 m every year.

Incorporating uncertainty into analyses of red-crested pochard habitat selection

Studies describing habitat use in animal species need to take into account detectability of individuals in order to reach more robust conclusions. However, the importance of detectability in habitat selection analyses of rare and cryptic species has received little investigation, although robust methods for estimating detectability have been made recently available. Understanding habitat requirements should be an important management tool for the conservation of the red-crested pochard ( Netta rufina), a rare duck species in France and Europe. Three different lake samples (82 lakes in total) were conjointly used in 2000 and 2001 to assess the species habitat requirements, using its presence, density and hatching dates as response variables. Risk of false absence was estimated using the double-observer approach at less than 0.001. A robust-design approach produced estimates of individual brood detectability (0.545, SE = 0.053). Observed red-crested pochard densities were adjusted to time dependent detectabilities, and modelled as a function of habitat variables. Habitat fragmentation and low permanent water levels negatively affected brood densities. Interestingly, these variables were not retained when modelling the unadjusted densities. This analysis showed that investigating temporal variation in brood detectability was a crucial prerequisite in the study of this rare species’ habitat requirements. More generally, it strongly suggests that integrating detection probability and its variations in habitat use analyses of cryptic species of conservation concern may be an essential methodological step to reach more valid conclusions on habitat management.

Ernst Mayr: 1904 – 2005

One Long Argument, the title of one of Ernst Mayr's later popular books on evolution, in many ways sums up the core of his intellectual life. Mayr, a leading evolutionary biologist over many years of the past century, who died aged 100 last month, was an explorer, naturalist, ornithologist, philosopher, historian of science and Harvard academic.Like Darwin, he was studying medicine when his focus was diverted to natural history. In his 20s he grasped opportunities for tropical expeditions and his travels shaped his life. His achievements were the result of being profoundly enthralled by the wonders of nature and applying his sharp inquisitive mind to finding logical answers, supported by scientific research.Mayr was a birdwatcher from childhood, influenced by his father, Otto. At 10, he could identify many species around the southern German town of Kempten. But the most significant event that year was his sighting of a pair of red-crested pochards, not recorded in Germany since 1846. He recalled that his life would have been completely different had it not been for those ducks.They brought him to the attention of Professor Erwin Stresemann, curator of birds at the Berlin Natural History Museum; Mayr was invited to work there during vacations, classifying tropical bird specimens. He recalled it was like being ‘given the keys to heaven.’An ornithology doctorate followed in 1925, and he became the museum's curator in 1926. At the 1927 International Zoological Congress at Budapest, he met the banker Lord Walter Rothschild, who had a private museum at Tring, in southern England. Rothschild was assembling the world's most comprehensive bird collection, and Mayr did not hesitate when offered the job of New Guinea staff naturalist. His 1928–29 experiences there included journeys through six unexplored mountain ranges.He was then invited to lead a 1929–30 expedition to the Solomon Islands, sponsored by the American philanthropist Harry Payne Whitney. This made important contributions to biology, discovered scores of species and filled a hall at New York's Museum of Natural History.View Large Image | View Hi-Res Image | Download PowerPoint SlideIn the early 1930s Mayr was briefly curator of Rothschild's Tring collection and might well have stayed in England. But when the banker plunged into financial crisis, 280,000 of his bird skins were sold to the New York museum. This was Mayr's base for 21 years – as the Whitney-Rothschild collection's associate curator from 1932 to 1944, and curator to 1953.View Large Image | View Hi-Res Image | Download PowerPoint SlideHis early work guided Theodosius Dobzhansky's Genetics and the Origin of Species (1937), which founded the synthetic theory of evolution. With Julian Huxley and George Gaylord Simpson, he helped incorporate new discoveries by naturalists and population geneticists into the framework of Darwinian theory.Harvard was important to the second half of his life, he was professor of zoology from 1953 to 1975 and also directed the university's Museum of Comparative Zoology from 1961 to 1970. His interest in evolutionary biology, and the history and philosophy of biology grew. His Animal Species and Evolution (1963) had new views on the nature of species.His later years were dominated by continuing his argument into the development of a philosophy of biology. Mayr was acutely aware of the distinction between biological principles and those of the physical sciences. As physical science had an increasing input into the workings of biology his plangent voice grew stronger. His one long argument, backed by a lifetime of solid practical work, is sure to endure. “I'm an old-time fighter for Darwinism,” he told the Harvard University Gazette in 1991. “I say: ‘Please tell me what is wrong with Darwinism. I don't see anything wrong.’”

Estimating breeding population size of the red‐crested pochard (Netta rufina) in the Camargue (southern France) taking into account detection probability: implications for conservation

AbstractThe red‐crested pochard (Netta rufina), a Eurasian diving duck, has seen its numbers declining and has received strong conservation concern. Data on population size and rate of decline are required to establish management plans, none of which is available for this species. Here we present the first population size estimate taking into account detection probability and habitat use in the Camargue, southern France. A non‐random sample of 33 lakes was used to estimate detection probability from point‐counts. Detectability was low, with only 57.5% of individual broods detected. A random sample of 37 lakes was then used to estimate brood densities. Adjusted densities (taking into account detection probability) were 0.1106 broods per ha of reedbed. Adjusted densities were extrapolated to the entire surface area of reedbeds in the Camargue estimated from a GIS to obtain abundance estimates of the brood population. A minimum estimate of 559 breeding pairs was obtained (95% confidence interval: 436–855). This estimate is much higher than previous ones (80–100 pairs for the Camargue, 250 pairs for France), and indicates strong underestimation of the population size when not taking into account detectability. Our results suggest that the red‐crested pochard may require a reassessment of its conservation status for France and Europe. They further suggest that taking detection probability into account in population estimates of other cryptic species, and notably those of conservation concern, may help clarify their conservation status and may even affect the setting of conservation priorities.

Estimating breeding population size of the red-crested pochard (Netta rufina) in the Camargue (southern France) taking into account detection probability: implications for conservation

Estimating breeding population size of the red-crested pochard (Netta rufina) in the Camargue (southern France) taking into account detection probability: implications for conservation

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

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

Response of herbivorous water-birds to the return of Chara in Lake Veluwemeer, The Netherlands

Water-birds were almost absent from Lake Veluwemeer during the 1970s and 1980s, due to low food availability related to eutrophication. Several restoration measures have resulted in the recolonization of the lake by Chara spp. during the 1990s. Bird numbers in autumn and winter have increased along with charophyte biomass. Linear regression analysis was used to relate bird numbers to the abundance of their potential food sources Chara, pondweeds, filamentous macro-algae (FA) and zebra mussels ( Dreissena polymorpha) within the depth range available to each species. Numbers of mute swan ( Cygnus olor), pochard ( Aythya ferina), tufted duck ( A. fuligula), coot ( Fulica atra) ( R 2≥0.98), gadwall ( Anas strepera) ( R 2=0.78), Bewick’s swan ( Cygnus columbianus) ( R 2=0.79), red-crested pochard ( Netta rufina) ( R 2=0.76) and pintail ( Anas acuta) ( R 2=0.38) showed significant correlations with these food sources. Chara biomass explained most of the variance in all species except for gadwall. Both bird numbers and their duration of stay were closely associated with the presence of Chara. Grazing pressure was low during spring and summer and Chara colonized the lake in spite of consumption. It is argued that birds did not slow down colonization of the lake by Chara during the 1990s, but may have accelerated succession from pondweeds Potamogeton spp. to charophytes. As more birds foraged on Chara compared to any other food resource, the preservation of large areas of Chara is of great importance to the water-bird community in Lake Veluwemeer.

Balzfüttern, Teilen oder tolerierter Diebstahl von Nahrung bei der Kolbenente (Netta rufina)?

Red-crested Pochards (Netta rufina) have been observed feeding on plants brought by their mates to the water surface, and this behaviour has been traditionally considered as courtship feeding. In this paper I report on this behaviour and examine its behavioural context. Females fed more frequently than males on plants brought by their mates to the surface, and this behaviour always occurred among paired birds. Individuals that procured the food plants were never observed offering them to their mates, but the latter simply approached the former as they surfaced with plants. The main advantages of this feeding behaviour would be to increase intake rates, as well as to reduce the feeding costs, as no time is spent searching for food underwater. Intake rates of individuals that procured the food were negatively affected when their mates profited from such food. Probably because of this, individuals that procured the food plants surfaced immediately after the feeding interaction with smaller quantities of food than before. This may be a strategy to discourage some individuals from feeding on plants brought to the surface by their mates, because this would allow the individuals that procure the food to ingest it before others start feeding on the plants. In this light, this feeding behaviour should not be considered as courtship feeding. Depending on whether pair bonds are maintained or split before breeding, this behaviour should be considered either as food sharing or tolerated food theft.

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.

Courtship feeding, food sharing, or tolerated food theft among paired Red-crested Pochards (Netta rufina)?

Courtship feeding, food sharing, or tolerated food theft among paired Red-crested Pochards (Netta rufina)?

Avian influenza in wild waterfowl and shorebirds in the Doñana National Park: Serological survey using the enzyme‐linked immunosorbent assay

The indirect ELISA was used to detect antibodies to influenzavirus A in the sera of wildfowl from the Donana National Park. Of the 712 birds examined, 44 (6.2%) were seropositive. Positive birds belonged to 10 of the 13 species studied. Infection rates varied widely: spoonbill (Platalea leucorodia, 32.2%), mallard (Anas platyrhynchos, 9.9%), gadwall (Anas strepera, 8.6%), red-crested pochard (Netta rufina, 8.1%), pochard (Aythya ferina, 6.4%), shoveler (Anas clypeata, 5%), great crested grebe (Podiceps cristatus, 4.3%), avocet (Recurvirostra avosetta, 3.1%), grey heron (Ardea cinerea, 3.1%) and coot (Fulica atra, 0.8%). Although infection rates were not high, the wide range of avian species susceptible to influenzavirus A suggests circulation of the virus amongst wildfowl at Donana.

Parasitic Laying in Red-Crested Pochard Netta rufina Nests

Parasitic Laying in Red-Crested Pochard Netta rufina Nests

Nest parasitism of PochardAythya ferinaby Red‐crested PochardNetta rufina

Nest parasitism of Pochard<i>Aythya ferina</i>by Red‐crested Pochard<i>Netta rufina</i>

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.

RECENT ORNITHOLOGICAL PUBLICATIONS

RECENT ORNITHOLOGICAL PUBLICATIONS

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.

Distribution of the Anserine Birds found in the Japanese Islands

The fourth and final part indicates known localities of fourteen species of the salt-water or diving ducks and three species of Mergansers or Sawbills. Very interesting addition is Netta rufina which was observed in the Fukui Prefecture, Japan.

A record sighting of the Red-Crested Pochard, Netta ruina (Pallae) in Japan

A record sighting of the Red-Crested Pochard, Netta ruina (Pallae) in Japan

Courtship of the Redhead (Aythya Americana)

THE annual cycle of the Redhead (Aythya americana) has been studied more intensively than that of most North American ducks. The species winters mainly on the Gulf and east coasts and breeds in the prairie pothole region of the northern United States and southern Canada and in the large marshes of the arid west (Weller, 1964). It nests over water in emergent vegetation and is inclined toward parasitic-laying (Low, 1945; Weller, 1959). Its weight cycle and plumages have been described (Weller, 1957) and related to the chronology of pair formation (Weller, 1965). The present paper integrates my observations with those of previous workers on the courtship displays and pairing activities of the species, presents some quantitative appraisal of the frequency and sequence of displays, and discusses their possible role in the breeding biology of the species. The earliest reported observations of the courtship of the Redhead seem to have been made by Wetmore (1920: 243-244), but it was Hochbaum (1944: 38-43) who described most of their displays comparatively in his study of the closely related Canvasback (Aythya valisineria). The only more intensive studies of the courtship of a pochard (Aythyini) are those of Lind (1958, 1962) on the Red-crested Pochard (Netta rujina). Recently, McKinney (1965) discussed comfort movements and their use as displays in this and other species, and Johisgard (1965: 232-234) has described Redhead displays performed on water. General courtship activities of Redheads were outlined by Low (1945) who noted that courtship was prevalent on certain large water areas and occurred mostly in the morning and evening. The observations reported here were made on breeding grounds at Delta, Manitoba (1952-1954, 1956), and Utah (1955); on wintering areas in Texas (late December and early January, late February and early March, 1960-61) and Chesapeake Bay and Cayuga Lake (February and March, 1954); and on the northward migration route in Iowa (1961, 1962, 1966) and in Illinois (March, 1957). Observations on some captives of all ages were made at the Delta Waterfowl Station. Work in Manitoba, Utah, and on the east coast was sponsored by the Delta Waterfowl Research Station and the Missouri Cooperative Wildlife Research Unit. Studies in Texas were financed by the American Academy of Arts and Sciences, the Welder Wildlife Foundation, and Iowa State University.

Studies on the relation of gonadic structure to plumage characterisation in the domestic fowl.—II. The developmental capon and poularde

Among the many sexually abnormal fowls sent to this Department during the last five years by poultry keepers interested in the science of breeding have been eleven birds which together form a distinct class. Instead of developing into normal cocks or hens with appropriate male or female plumage and head furnishings as they approached maturity, these birds assumed, and retained throughout their lives, the characters and behaviour of the fowl completely gonadectomised before puberty. There was never any reason to assume that the underlying physiological inactivity or actual absence of the gonads was other than the result of some developmental disharmony. No sign or history of disease was ever presented. Our knowledge of the adult characterisation of the fowl experimentally gonadectomised when a few days old, allowed us to recognise that in this group of sexually abnormal birds there were genetic males and females in which the gonadic tissues had been absent or functionally insufficient throughout their lives. In one respect only did these birds (save one) differ from the experimental capon and poularde; their combs were not bloodless and scaly, they were bright and healthy-looking, though very diminutive. After having been kept under observation for two years or more, the birds were killed. Post-mortem examination confirmed our anticipations. In all, there was either complete suppression or else very considerable reduction of gonadic tissue. Such cases as these have an important bearing upon the problem of the relation of gonadic structure and function to plumage characterisation in the fowl. The following cases of gonadic suppression and reduction in birds have been recorded : one duck, Netta rufina, with imperfect male characters and no gonads (Poll, 1909); four pheasant hybrids, Phasianus torquatus X P . colchicus (?) (Smith and Haig Thomas, 1913); Syrmatiens recessi X Phasianus principalis , reciprocal crosses, all females had small flaccid oviduct but no gonadic tissue (Phillips, 1916); pigeons and ringdoves, pure bred and hybrid, sixteen with no gonads, fifteen in which one gonad was abnormally absent, seventeen in which various degrees of reduction in the size of the gonads were exhibited (Riddle, 1925).