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  • 1.
    Arzel, C.
    et al.
    Kristianstad University, Department of Mathematics and Science.
    Elmberg, Johan
    Kristianstad University, Department of Mathematics and Science.
    Guillemain, M.
    Office National de la Chasse et de la Faune Sauvage, CNERA Avifaune Migratrice, La Tour du Valat, Le Sambuc, Arles.
    A flyway perspective of foraging activity in Eurasian Green-winged Teal, Anas crecca crecca2007In: Canadian Journal of Zoology, ISSN 0008-4301, E-ISSN 1480-3283, Vol. 85, no 1, 81-91 p.Article in journal (Refereed)
    Abstract [en]

    Time-activity budgets in the family Anatidae are available for the wintering and breeding periods. We present the first flyway-level study of foraging time in a long-distance migrant, the Eurasian Green-winged Teal, Anas crecca crecca L., 1758 ("Teal"). Behavioral data from early and late spring staging, breeding, and molting sites were collected with standardized protocols to explore differences between the,sexes, seasons, and diel patterns. Teal foraging activity was compared with that of the Mallard, Anas platyrhynchos L., 1758 and Northern Shoveler, Anas clypeata L., 1758, and the potential effects of duck density and predator-caused disturbance were explored. In early spring, foraging time was moderate (50.5%) and mostly nocturnal (45%). It increased dramatically in all three species at migration stopovers and during molt, mostly because of increased diurnal foraging, while nocturnal foraging remained fairly constant along the flyway. These patterns adhere to the "income breeding" strategy expected for this species. No differences between the sexes were recorded in either species studied. Teal foraging time was positively correlated with density of Teal and all ducks present, but negatively correlated with predator disturbance. Our study suggests that Teal, in addition to being income breeders, may also be considered as income migrants; they find the energy necessary to migrate at staging sites along the flyway.

  • 2.
    Elmberg, Johan
    Department of Animal Ecology, University of Umeå.
    Long-term survival, length of breeding season, and operational sex ratio in a boreal population of common frogs, Rana temporaria L.1990In: Canadian Journal of Zoology, ISSN 0008-4301, E-ISSN 1480-3283, Vol. 68, no 1, 121-127 p.Article in journal (Refereed)
    Abstract [en]

    A population of individually marked adult Rana temporaria was studied during the breeding season in 1979–1988 in east-central Sweden. Annual return rate averaged 31% (range 16–51%) in males and 16% (range 5–33%) in females. Return rate was not size dependent but increased with every successful previous hibernation, indicating an increased survival rate with age. Return rate was not correlated with winter harshness. Once adult, males had on average 1.5 (maximum 6) seasons with the possibility of reproducing. Corresponding values for females were 1.4 and 4. Mean length of the breeding season was 20 (SD = 2) days. Calling generally started at water temperatures below 3 °C. The lowest spawning temperature was 1 °C. Average temperatures at spawning onset and peak spawning were 5 and 6 °C, respectively. Large males tended to arrive earlier at the pond than small males. Males arrived earlier and stayed longer than did females. The overall population sex ratio was close to unity. The operational sex ratio (OSR) varied during the breeding season, averaging 0.54 (one female to two males). No male was observed to mate more than once per season. I argue that survival selection is more important to male lifetime mating success than is competition in the breeding pond (sexual selection as affected by OSR and length of the breeding season).

  • 3.
    Elmberg, Johan
    et al.
    Kristianstad University, Department of Mathematics and Science.
    Gunnarsson, Gunnar
    Kristianstad University, Department of Mathematics and Science.
    Manipulated density of adult mallards affects nest survival differently in different landscapes2007In: Canadian Journal of Zoology, ISSN 0008-4301, E-ISSN 1480-3283, Vol. 85, no 5, 589-595 p.Article in journal (Refereed)
    Abstract [en]

    Breeding success in many birds including wildfowl is mainly determined by nest predation. Few studies address cues used by predators to find duck nests, and the same is true for spacing patterns that ducks might use to reduce predation. We designed a crossover experiment in agricultural and forested settings to test the assumption that nest predation rate is related to density of adult birds on a lake. We used introduced wing-clipped mallards (Anas platyrhynchos L., 1758) to increase local pair density and semi-natural nests to assess predation rate. Depredation patterns were analyzed by model fitting in program MARK, using introduction and landscape type as main effects and abundance of avian predators and wild waterbirds as covariates. Depredation was higher at agricultural lakes than at forest lakes. Nest survival decreased with increasing abundance of wild waterfowl, whereas it tended to increase with the abundance of "other waterbirds". There was a landscape-dependent effect of increased mallard pair density: positive at agricultural lakes and negative at forest lakes. Avian predators found 91% of depredated "known-predator" nests at agricultural lakes and 25% at forest lakes; mammals found 9% at agricultural lakes and 75% at forest lakes. The landscape-dependent density effect may in part be due to different predator communities in these landscape types.

  • 4.
    Elmberg, Johan
    et al.
    Kristianstad University, School of Education and Environment.
    Pöysä, Hannu
    Finnish Game and Fisheries Research Institute, Joensuu Game and Fisheries Research.
    Is the risk of nest predation heterospecifically density-dependent in precocial species belonging to different nesting guilds?2011In: Canadian Journal of Zoology, ISSN 0008-4301, E-ISSN 1480-3283, Vol. 89, no 12, 1164-1171 p.Article in journal (Refereed)
    Abstract [en]

    Nest predation is a key source of mortality and variation in fitness, but the effect co-occurring species belonging to different nesting guilds have on each other’s nest success is poorly understood. By using artificial nests, we tested if predation on cavity nests of Common Goldeneyes (Bucephala clangula (L., 1758)) is increased in the presence of ground nests of Mallards (Anas platyrhynchos L., 1758) and vice versa. Specifically, by adding ground nests in the vicinity of cavity nests, we tested the hypothesis that predation on cavity nests is heterospecifically density-dependent. A shared predator, the pine marten (Martes martes (L., 1758)), was intensively hunted in one of the study areas, but not in the other, leading to most individuals in the former being naïve immigrants. Cavity-nest fate was not affected by addition of ground nests. Similarly, ground-nest survival did not decrease when nearby cavity nests were depredated. Fate of nests in a given nest cavity was highly predictable between years in the study area with minimal removal of pine martens, but not in the one with intensive removal. Predation rate was higher on cavity nests than on ground nests. Predation on ground nests was lower in the study area with intensive removal of pine martens. We conclude there was neither apparent competition between guilds nor heterospecific density-dependence in predation risk.

  • 5.
    Gunnarsson, Gunnar
    et al.
    Kristianstad University, Department of Mathematics and Science.
    Elmberg, Johan
    Kristianstad University, Department of Mathematics and Science.
    Sjöberg, Kjell
    Department of Animal Ecology, Swedish University of Agricultural Sciences, Umeå.
    Pöysä, Hannu
    Finnish Game and Fisheries Research Institute, Joensuu Game and Fisheries Research.
    Nummi, Petri
    Department of Applied Biology, University of Helsinki.
    Why are there so many empty lakes?: food limits survival of mallard ducklings2004In: Canadian Journal of Zoology, ISSN 0008-4301, E-ISSN 1480-3283, Vol. 82, no 11, 1698-1703 p.Article in journal (Refereed)
    Abstract [en]

    Food is an important factor affecting survival in many bird species, but this relationship has rarely been explored experimentally with respect to reproductive output of precocial birds. In a field experiment we tested the hypothesis that food abundance limits reproductive output in breeding dabbling ducks. Onto 10 oligotrophic lakes in northern Sweden we introduced one wing-clipped female mallard (Anas platyrhynchos L., 1758) and a brood of 10 newly hatched ducklings, and survival was monitored for 24 days. Food was added ad libitum at five of the lakes, but not at the other five. Duckling survival was best modelled to include a treatment effect, with higher survival on lakes with food added, and a negative effect of harsh weather. As expected, duckling survival increased nonlinearly with age. Only one female remained on control lakes after 24 days, whereas four remained on lakes with food added. This is the first experimental demonstration that food may limit survival and reproductive output in breeding precocial birds. We argue that food limitation may be one reason why duckling mortality is high and why many lakes throughout the Holarctic have no breeding dabbling ducks.

  • 6. Lacoursière, Jean O.
    A laboratory study of fluid flow and microhabitat selection by larvae of Simulium vittatum (Diptera: Simuliidae)1992In: Canadian Journal of Zoology, ISSN 0008-4301, E-ISSN 1480-3283, Vol. 70, no 3, 582-596 p.Article in journal (Refereed)
    Abstract [en]

    Microhabitat selection by Simulium vittatum Zetterstedt larvae in a flume was studied at different mainstream velocities on two substrates; a thin flat plate parallel to the flow and a cylinder in cross flow. The results do not support the generally accepted assumptions that simuliid larvae keep within the boundary layer to avoid the direct influence of mainstream current and that they select the fastest velocity available when offered a longitudinal velocity gradient within their tolerance range. Instead, larvae gathered along the zone of boundary layer separation and remained along the stagnation line at the leading point of the cylinder when artificially positioned there. Further, under most conditions, larvae avoided zones of maximum surface shear stress. Larval reaction to hydraulic changes was immediate. It is hypothesized that S. vittatum larvae first scan the velocity profile at the substrate, initially moving toward increasing flow velocity (or water acceleration). They than cue on a steep velocity gradient along the body as part of the processes involved in choosing a location for suspension feeding.

  • 7. Lacoursière, Jean O.
    et al.
    Craig, DA
    Fluid transmission and filtration efficiency of the labral fans of black fly larvae (Diptera: Simuliidae): Hydrodynamic, morphological, and behavioural aspects1993In: Canadian Journal of Zoology, ISSN 0008-4301, E-ISSN 1480-3283, Vol. 71, no 1, 148-162 p.Article in journal (Refereed)
    Abstract [en]

    Body stance and water flow through the labral fans of suspension-feeding Simulium vittatum Zetterstedt larvae were examined using dead and live larvae. Transmission of flowing water through the fans were determined by means of dye injections. Feeding stance is the outcome of an active feedback process between flow forces and behavioural reactions that maintains the fans in an optimal filtering position. Fans responded to velocity increases through structural reconfiguration, which resulted in an increase in aperture size. As the velocity decreased, an increased fraction of the water directly approaching the fan aperture flowed around its perimeter, with no flow through the fans below 2.5 cm/s. Fluid transmission never exceeded 30-35%, even at velocities up to 50 cm/s. Calculations of suspension-feeding efficiency are reformulated to reflect labral fan transmission and behavioural components of the feeding process. Simulium vittatum larvae are consequently showed to be 4-26 times more efficient in filter feeding than has been previously assessed. The effect of flow on labral fan transmission is discussed in relation to known habitat choices and feeding behaviours of simuliid larvae.

  • 8.
    Nummi, Petri
    et al.
    Department of Applied Zoology, University of Helsinki.
    Sjöberg, Kjell
    Department of Animal, Ecology, Swedish University of Agricultural Sciences, Umeå.
    Pöysä, Hannu
    Finnish Game and Fisheries Research Institute, Evo Game Research Station.
    Elmberg, Johan
    Department of Animal, Ecology, Swedish University of Agricultural Sciences, Umeå.
    Individual foraging behaviour indicates resource limitation: an experiment with mallard ducklings2000In: Canadian Journal of Zoology, ISSN 0008-4301, E-ISSN 1480-3283, Vol. 78, no 11, 1891-1895 p.Article in journal (Refereed)
    Abstract [en]

    The linkage between individual behaviour and population processes has recently been emphasized. Within this framework we studied the effect of resource limitation on the behaviour of mallard (Anas platyrhynchos) ducklings in boreal lakes. One group of 12 human-imprinted ducklings (4-16 days old) were taken to 11 "rich" lakes, i.e., with a relatively high concentration of total phosphorus in the water, and the other group of 12 ducklings to 11 "poor" lakes to forage for a period of 6 h. During this, a time budget study lasting 5 min was done of each of the 12 ducklings. In the rich lakes, ducklings fed significantly more and moved less than in the poor ones. This difference was particularly striking in above-surface feeding. Variation in foraging performance was associated with change in body mass of the ducklings: the less distance the ducklings moved and the more they fed above water, the more they gained mass. Earlier results had suggested that at least some of the boreal wetlands that lack duck broods year after year (70% of the total in one study) do so because they do not harbour enough food. Hence, it is possible that mallard populations are resource-limited at the brood stage during the breeding season.

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