The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform

Leif Nilsson - One of the best experts on this subject based on the ideXlab platform.

  • wintering Diving Duck populations in the oresund southern sweden in relation to available food resources
    Wildfowl; 55 pp 61-76 (2005), 2005
    Co-Authors: Leif Nilsson
    Abstract:

    Intensive surveys of staging and wintering Diving Ducks in the Oresund area,southern Sweden, were undertaken during the winters 1995/96, 1996/97 and1997/98 as a part of the Environmental Impact Assessment (EIA) related to theestablishment of a Fixed Link (bridge–tunnel–artificial island) between Swedenand Denmark. Monitoring of the benthic fauna made it possible to compare thecalculated food requirements of the Diving Duck populations with their foodresources. Overall, the Diving Ducks (mainly Tufted Duck Aythya fuligula, ScaupAythya marila and Goldeneye Bucephala clangula) consumed between 2.6% and4.6 % of the standing crop of suitable food organisms. It is, however, probable that higher proportions of the prey are consumed in the shallowest areas compared to areas with deeper water. A prolonged period of ice cover during one of the study years made a large proportion of the feeding areas unavailable, but the main mussel beds were still free of ice because of strong currents so this had only limited impact on the food availability for the Ducks.

Jean-yves Mondain-monval - One of the best experts on this subject based on the ideXlab platform.

  • Estimating breeding population size of the red‐crested pochard (Netta rufina) in the Camargue (southern France) taking into account detection probability: implications for conservation
    Animal Conservation, 2003
    Co-Authors: Christophe Barbraud, Jean-yves Mondain-monval
    Abstract:

    The red-crested pochard, 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 hectare 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
    Animal Conservation, 2003
    Co-Authors: Pierre Defos Du Rau, Christophe Barbraud, Jean-yves Mondain-monval
    Abstract:

    The red-crested pochard, 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 hectare 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 concer

Werner Suter - One of the best experts on this subject based on the ideXlab platform.

  • Overwintering waterfowl on Swiss lakes: how are abundance and species richness influenced by trophic status and lake morphology?
    Hydrobiologia, 1994
    Co-Authors: Werner Suter
    Abstract:

    Mean waterfowl populations (1976–1987) on the 20 major Swiss lakes north of the Alps were analysed in order to identify lake characteristics which shape waterfowl populations. Abundance and species richness are linear (abundance) and power functions (species richness) of lake area or shore-length, according to waterfowl guild. The remaining variation can partly be explained by variables related to the available food (coarse fish yield for piscivorous species) or the suitability for foraging (shallow areas and percentage of natural, open shoreline for dabbling Ducks). Reedbelts are not important per se . There are no unequivocal relationships with the trophic status, since lakes with low waterfowl densities or species numbers are found among all trophic levels. However, mean and maximum species richness increase with nutrient load. Maximum bird densities increase from oligotrophic to meso-/eutrophic lakes in all guilds. Hypertrophic lakes may also have high densities of fisheaters because of the large populations of Cyprinid fish present. Diving Duck densities are much lower in hypertrophic than in less nutrient-loaded lakes, since their main food, the bivalve Dreissena polymorpha , prefers less eutrophicated lakes. Food abundance and availability seems to be the main factor governing lake choice by overwintering waterfowl, although other factors such as disturbance levels may not have been detected by this broad-scale analysis.

Pierre Defos Du Rau - One of the best experts on this subject based on the ideXlab platform.

  • Estimating breeding population size of the red-crested pochard (Netta rufina) in the Camargue (southern France) taking into account detection probability: implications for conservation
    Animal Conservation, 2003
    Co-Authors: Pierre Defos Du Rau, Christophe Barbraud, Jean-yves Mondain-monval
    Abstract:

    The red-crested pochard, 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 hectare 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 concer

Christophe Barbraud - One of the best experts on this subject based on the ideXlab platform.

  • Estimating breeding population size of the red‐crested pochard (Netta rufina) in the Camargue (southern France) taking into account detection probability: implications for conservation
    Animal Conservation, 2003
    Co-Authors: Christophe Barbraud, Jean-yves Mondain-monval
    Abstract:

    The red-crested pochard, 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 hectare 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
    Animal Conservation, 2003
    Co-Authors: Pierre Defos Du Rau, Christophe Barbraud, Jean-yves Mondain-monval
    Abstract:

    The red-crested pochard, 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 hectare 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 concer