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  • 201.
    Nilsson, Anders N.
    et al.
    Department of Animal Ecology, University of Umeå.
    Elmberg, Johan
    Department of Ecology, Swedish University of Agricultural Sciences, Umeå.
    Sjöberg, Kjell
    Game Division, Finnish Game and Fisheries Research Institute, Helsinki.
    Abundance and species richness patterns of predaceous diving beetles (Coleoptera, Dytiscidae) in Swedish lakes1994In: Journal of Biogeography, ISSN 0305-0270, E-ISSN 1365-2699, Vol. 21, no 2, p. 197-206Article in journal (Refereed)
    Abstract [en]

    Abundance and species richness of dytiscid water beetles were estimated with activity traps in ten lakes each in south, central and north Sweden. Partial least square regression models with two significant components explained 76.5% and 55.8% of the total variance in dytiscid abundance and species richness, respectively. For abundance as well as species richness, component 1 had its highest positive loadings for structural complexity of vegetation and abundance of Asellus and Diptera immatures, and high negative loadings for relative shore depth. Component 2 had its highest positive loadings for fish abundance, number of dipterans in emergence traps and relative shore depth, and high negative loadings for lake area. Both the number of dytiscid individuals and species were higher in the northern lakes than in the two other regions. Smaller species were not more abundant in the traps than larger ones. Species mean abundance was positively correlated with number of lakes occupied.

  • 202.
    Nudds, Thomas D.
    et al.
    Canada.
    Elmberg, Johan
    SLU.
    Pöysä, Hannu
    Finland.
    Sjöberg, Kjell
    SLU.
    Nummi, Petri
    Finland.
    Ecomorphology and coexistance in breeding holarctic dabbling ducks2000Conference paper (Refereed)
    Abstract [en]

    We have debated the effects of interspecific competition, especially in ecological time, on the distribution and abundance of dabbling ducks (Anas spp.), and the relative importance of bill morphology and body size in facilitating coexistence. Evidence from North American and Baltic coastal wetlands indicates that species with few lamellae (but longer bodies) tend to feed in shallow, vegetated microhabitats where invertebrate prey is large; species with dense lamellae (but shorter bodies) tend to feed offshore where prey is smaller. In northern Europe, however, the evidence is opposite, suggesting that differences in body length instead facilitate coexistence. Here, we present evidence that these views are compatible under a refined conceptual model. In both northern Europe and North America, microhabitat diversity within wetlands correlates with a-diversity (species per wetland). With increasing latitude, a-diversity decreases, coincident with changes in the shape of wetland basins from largely "saucer-" (prairie/steppe potholes) to "bowl-shaped" (nemoral/ boreal lakes and tarns). We propose that (1) there is less absolute microhabitat (water-depth/vegetation) gradient along which species can be accommodated in northern wetlands, owing to shoreline steepness, and (2) body length is more important in facilitating species co-existence among breeding dabbling ducks in "bowl-shaped" wetlands, whereas lamellar density is more important in "saucer-shaped" wetlands.

  • 203.
    Nudds, Thomas D.
    et al.
    Deptartment of Zoology, University of Guelph.
    Elmberg, Johan
    Deptartment of Animal Ecology, Swedish University of Agricultural Sciences, Umeå.
    Sjöberg, Kjell
    Deptartment of Animal Ecology, Swedish University of Agricultural Sciences, Umeå.
    Pöysä, Hannu
    Game and Fisheries Research Institute, Evo Game Research Station.
    Nummi, Petri
    Deptartment of Applied Zoology, University of Helsinki.
    Ecomorphology in breeding Holarctic dabbling ducks: the importance of lamellar density and body length varies with habitat type2000In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 91, no 3, p. 583-588Article in journal (Refereed)
  • 204.
    Nummi, Petri
    et al.
    Helsinki University.
    Elmberg, Johan
    Kristianstad University, Department of Mathematics and Science.
    Pöysä, Hannu
    Gunnarsson, Gunnar
    Kristianstad University, Department of Mathematics and Science.
    Sjöberg, Kjell
    Sveriges Lantbruksuniversitet, Umeå.
    Varhaiset tavipoikueet asuttavat suotuisimmat laikut ja menestyvät parhaiten2005In: Suomen Riista, ISSN 0355-0656, Vol. 51, p. 1685-1692Article in journal (Refereed)
  • 205.
    Nummi, Petri
    et al.
    Finland.
    Elmberg, Johan
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap.
    Pöysä, Hannu
    Finland.
    Sjöberg, Kjell
    SLU, Umeå.
    Breeding success of boreal mallard and wigeon in relation to population density and food resources2003In: Third North American duck symposium: waterfowl management and biology in the 21st century: looking back and to the future, 2003, p. 79-Conference paper (Refereed)
    Abstract [en]

    Breeding success of mallard and wigeon was studied for 12 years in a boreal lake area in southern Finland. Aquatic and surface-emerging prey were trapped to obtain annual indices of food abundance. The average density of mallards was 0.42 pairs per 1000 m shore line and that of wigeon 0.18. The mean brood production per pair was 0.24 in mallard and 0.41 in wigeon. We correlated brood:pair and duckling:pair ratios to pair density and per capita food availability to test whether per capita breeding success decreases in a density-dependent way when pair density or the number of nesting pairs per available food unit increases. No density-dependent pattern was found in mallards. In wigeon, in contrast, we found two independent patterns of density dependence. Per capita brood production correlated negatively with pair density, and brood:pair and especially duckling:pair ratio correlated negatively with per capita abundance of surfaceemerging prey.

  • 206.
    Nummi, Petri
    et al.
    Department of Applied Zoology, University of Helsinki.
    Elmberg, Johan
    Department of Animal Ecology, Swedish University of Agricultural Sciences, Umeå.
    Pöysä, Hannu
    Finnish Game and Fisheries Research Institute, Evo Game Research Station.
    Sjöberg, Kjell
    Department of Animal Ecology, Swedish University of Agricultural Sciences, Umeå.
    Occurrence and density of mallard and green-winged teal in relation to prey size distribution and food abundance1995In: Annales Zoologici Fennici, ISSN 0003-455X, E-ISSN 1797-2450, Vol. 32, no 4, p. 385-390Article in journal (Refereed)
    Abstract [en]

    We studied patterns of prey size and abundance among 60 lakes that differed with respect to occupancy by mallards (Anas platyrhynchos) and teal (A. crecca crecca). Size distributions of prey in lakes with and without mallards did not differ in the way they deviated from the prey size distribution found in the average diet of the species; the same was true also for teal. However, in lakes with abundant food, average teal diet differed more from what was found in the environment than in lakes with less prey; in the mallard there were no differences in this respect. The densities of mallard and teal correlated positively rather than negatively with each other irrespective of food abundance, suggesting that interspecific competition, at least in ecological time, between the species may not be important in determing their abundance and distribution.

  • 207. Nummi, Petri
    et al.
    Pöysä, Hannu
    Elmberg, Johan
    Kristianstad University, School of Education and Environment.
    Sjöfåglar: en flyttande internationell viltresurs2009In: Jägaren, ISSN 0355-2683, Vol. 58, no 5, p. 80-81Article in journal (Other (popular science, discussion, etc.))
  • 208. Nummi, Petri
    et al.
    Pöysä, Hannu
    Elmberg, Johan
    Kristianstad University, School of Education and Environment.
    Vesilinnut: muuttava kansainvälinen riistavara2009In: Metsästäjä, ISSN 0047-6986, Vol. 58, no 5, p. 80-81Article in journal (Other (popular science, discussion, etc.))
  • 209.
    Nummi, Petri
    et al.
    Department of Applied Zoology, University of Helsinki.
    Pöysä, Hannu
    Evo Game Research Station, Finnish Game and Fisheries Research Institute.
    Elmberg, Johan
    Department of Animal Ecology, Swedish University of Agricultural Sciences, Umeå.
    Sjöberg, Kjell
    Department of Animal Ecology, Swedish University of Agricultural Sciences, Umeå.
    Habitat distribution of the mallard in relation to vegetation structure, food, and population density1994In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 280, no 1, p. 247-252Article in journal (Refereed)
    Abstract [en]

    The mallard (Anas platyrhynchos Linnaeus) is a generalist feeder, breeding in a wide range of habitats, yet showing considerable between site differences in density. Variations in density and habitat use may result from inter- and intra-specific competition, habitat structure or food. We studied habitat selection of the mallard in four regions of Finland and Sweden. In each region, ten lakes were chosen ranging from oligotrophic to eutrophic. Habitat distribution of the mallard did not differ between regions despite variation in the density of the species and congenerics. Mallard density did not correlate with vegetation structure, but increased with food abundance and the number and density of congenerics although there were regional differences in mallard response.

  • 210.
    Nummi, Petri
    et al.
    Finland.
    Pöysä, Hannu
    Finland.
    Sjöberg, Kjell
    SLU.
    Elmberg, Johan
    SLU.
    Gräsandungar tjänar forskningen2000In: Jägaren, ISSN 0283-8109, Vol. 49, no 3, p. 26-28Article in journal (Other (popular science, discussion, etc.))
  • 211.
    Nummi, Petri
    et al.
    Finland.
    Pöysä, Hannu
    Finland.
    Sjöberg, Kjell
    SLU.
    Elmberg, Johan
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap.
    Sinisorsan poikasia tutkimuksen palveluksessa2000In: Metsästäjä, ISSN 0047-6986, Vol. 49, no 3, p. 26-28Article in journal (Other (popular science, discussion, etc.))
  • 212.
    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, p. 1891-1895Article 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.

  • 213. Nummi, R.
    et al.
    Pöysä, H.
    Elmberg, Johan
    Kristianstad University, School of Education and Environment.
    Dessborn, Lisa
    Kristianstad University, School of Education and Environment.
    Sjöberg, K.
    Ravinnon ja ympäristön rakenteen merkitys puolisukeltajasorsien poikueille2010In: Suomen Riista, ISSN 0355-0656, Vol. 56, p. 16-25Article in journal (Refereed)
  • 214.
    Olsson, Camilla
    et al.
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap. Kristianstad University, Research environment Man & Biosphere Health (MABH).
    Gunnarsson, Gunnar
    Kristianstad University, Research environment Man & Biosphere Health (MABH). Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap.
    Elmberg, Johan
    Kristianstad University, Research environment Man & Biosphere Health (MABH). Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap.
    Field preference of Greylag geese Anser anser during the breeding season2017In: European Journal of Wildlife Research, ISSN 1612-4642, E-ISSN 1439-0574, Vol. 63, article id 28Article in journal (Refereed)
    Abstract [en]

    Few studies address food preference of geese on agricultural land (utilization related to availability) and only a handful so for the breeding season. We studied Greylag geese Anser anser during the breeding season in an intensively farmed area in southern Sweden. Few of 22 available field types were truly preferred. Pastureland was the most consistently preferred, by goslings (with parents) as well as by nonbreeders. In some sampling periods, goslings also preferred grazed hay, ley, and carrot fields. Non-breeders exploited a greater variety of crops/fields, feeding also on barley, fallow, grazed hay, lettuce, oats, potatoes, and carrots. Most of these crops were preferred on at least one sampling occasion, except for fallow, grazed hay, and wheat, which were always used less than expected from availability. GLMs revealed that goslings rested more than they fed and preferred shorter vegetation before higher. Moreover, goslings occurred in higher densities in younger age classes than in older and preferred nearshore areas. In contrast, density of non-breeders was only related to field type and sampling occasion (higher densities as the season progressed). The maximum number of broods observed (106) implies a breeding success of 34% based on311 active nests earlier in the season. Brood size decreased from 3.5 to 2.1 during the study period. Our study shows that goose management during the breeding season should consider goslings and their parents separately from non-breeders, and it implies little potential conflict between Greylag geese and agriculture during the breeding period.

  • 215. Ottosson, Ulf
    et al.
    Ottvall, Richard
    Elmberg, Johan
    Kristianstad University, School of Education and Environment.
    Green, Martin
    Gustafsson, Rolf
    Haas, Fredrik
    Holmqvist, Niklas
    Lindström, Åke
    Nilsson, Leif
    Svensson, Mikael
    Svensson, Sören
    Tjernberg, Martin
    Fåglarna i Sverige: antal och förekomst2012Book (Other academic)
  • 216.
    Ottvall, Richard
    et al.
    Department of Ecology, Lund University.
    Edenius, Lars
    Department of Wildlife, Fish and Environmental Studies, Swedish University of Agricultural Sciences, Umeå.
    Elmberg, Johan
    Kristianstad University, School of Education and Environment.
    Engström, Henri
    Department of Ecology and Evolution, Uppsala University.
    Green, Martin
    Department of Ecology, Lund University.
    Holmqvist, Niclas
    Swedish Association for Hunting and Wildlife Management, Nyköping.
    Lindström, Åke
    Department of Ecology, Lund University.
    Pärt, Tomas
    Department of Ecology, Swedish University of Agricultural Sciences, Uppsala.
    Tjernberg, Martin
    Species Information Centre, Swedish University of Agricultural Sciences, Uppsala.
    Population trends for Swedish breeding birds2009In: Ornis Svecica, ISSN 1102-6812, Vol. 19, no 3, p. 117-192Article in journal (Refereed)
    Abstract [en]

    We have assessed the population trends for the 255 bird species breeding in Sweden (including distinct subspecies), based on data for the last 30 and 10 years, respectively. Over the past 30 years more species have decreased (38%) than increased (32%) in numbers. In particular, formerly common farmland species have fared poorly but this is also true for some forest species. Over the past 10 years there are more species with increasing trends (29%) than there are species with decreasing trends (19%). Trends for several species in long-term decline have levelled off and have in some cases even started to increase. It is not known whether this recent change is a result of conservation efforts or simply that population numbers have stabilised at lower levels now permitted by the environment. It is therefore essential to initiate research devoted to finding factors directly linked to ongoing population changes, particularly for species in longterm decline. To cover population trends for all Swedish species additional monitoring programmes are needed, in particular on owls and in mountain habitats.

  • 217.
    Ottvall, Richard
    et al.
    Lunds universitet.
    Edenius, Lars
    SLU, Umeå.
    Elmberg, Johan
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap.
    Engström, Henri
    Umeå universitet.
    Green, Martin
    Lunds universitet.
    Holmqvist, Niklas
    Svenska Jägareförbundet, Nyköping.
    Lindström, Åke
    Lunds universitet.
    Tjernberg, Martin
    SLU, Uppsala.
    Pärt, Tomas
    SLU, Uppsala.
    Populationstrender för fågelarter som häckar i Sverige2008Report (Other academic)
  • 218.
    Pöysä, Hannu
    et al.
    Finnish Game and Fisheries Research Institute, Joensuu Game and Fisheries Research.
    Dessborn, Lisa
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap. Kristianstad University, Forskningsmiljön Man and Biosphere Health (MABH).
    Elmberg, Johan
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap. Kristianstad University, Forskningsmiljön Man and Biosphere Health (MABH).
    Gunnarsson, Gunnar
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap. Kristianstad University, Forskningsmiljön Man and Biosphere Health (MABH).
    Nummi, Petri
    Department of Forest Sciences, University of Helsinki.
    Sjöberg, Kjell
    Department of Wildlife, Fish, and Environmental Studies, Swedish University of Agricultural Sciences, Umeå.
    Suhonen, Sari
    Department of Forest Sciences, University of Helsinki.
    Söderquist, Pär
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap. Kristianstad University, Forskningsmiljön Man and Biosphere Health (MABH).
    Harvest mortality in North American mallards: a reply to Sedinger and Herzog2013In: Journal of Wildlife Management, ISSN 0022-541X, E-ISSN 1937-2817, Vol. 77, no 4, p. 653-654Article in journal (Refereed)
    Abstract [en]

    Sedinger and Herzog (2012) evaluated the evidence for the impact harvest mortality may have on North American duck populations. While doing that, they questioned our review (Pöysä et al. 2004) and conclusion that harvest mortality in North American mallards (Anas platyrhynchos) may have shifted from compensatory to additive over the period from the 1960s to the 1980s. In this reply, we correct Sedinger and Herzog's misrepresentations of our 2004 paper and argue that our interpretations of the results published at that time have not been invalidated.

  • 219.
    Pöysä, Hannu
    et al.
    Finland.
    Elmberg, Johan
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap. Kristianstad University, Research environment Man & Biosphere Health (MABH).
    Gunnarsson, Gunnar
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap. Kristianstad University, Research environment Man & Biosphere Health (MABH).
    Holopainen, Sari
    Finland.
    Nummi, Petri
    Finland.
    Sjöberg, Kjell
    SLU, Uppsala.
    Habitat associations and habitat change: seeking explanation for population decline in breeding Eurasian wigeon Anas penelope2017In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 785, no 1, p. 207-217Article in journal (Refereed)
    Abstract [en]

    We explored whether the recent large-scale population decline of Eurasian wigeon (Anas penelope) in Europe may be linked to long-term vegetation changes in their boreal breeding wetlands. First, we assessed the importance of Equisetum, Phragmites, and Carex stands in lake selection by pairs and in foraging habitat selection by broods. Second, in 2013–2014 we revisited 58 lakes in Sweden and Finland studied in 1990–1991, to examine if there had been any long-term change in the abundance of habitat types preferred by wigeon. Finally, using continuous long-term data on breeding numbers of wigeon in 18 of the lakes studied in 1990–1991, we examined if wigeon numbers had changed at lakes where the habitat also had changed. We found that lake occupation of nesting wigeon pairs and foraging habitat use of broods were associated with the extent of Equisetum stands. The presence and abundance of this preferred habitat declined dramatically from 1990–1991 to 2013–2014 in the lakes from which the presence–absence data of wigeon emanate. Breeding numbers of wigeon showed a long-term declining trend in lakes where Equisetum has decreased. Our results imply that the recent population decline of wigeon in Europe may be linked to decrease of Equisetum habitat.

  • 220.
    Pöysä, Hannu
    et al.
    Finnish Game and Fisheries Research Institute, Joensuu Game and Fisheries Research.
    Elmberg, Johan
    Kristianstad University, Department of Mathematics and Science.
    Gunnarsson, Gunnar
    Kristianstad University, Department of Mathematics and Science.
    Nummi, Petri
    Department of Applied Biology, University of Helsinki.
    Sjöberg, Kjell
    Department of Animal Ecology, Swedish University of Agricultural Sciences, Umeå.
    Ecological basis of sustainable harvesting: is the prevailing paradigm of compensatory mortality still valid?2004In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 104, no 3, p. 612-615Article in journal (Refereed)
  • 221.
    Pöysä, Hannu
    et al.
    Finnish Game and Fisheries Research Institute, Evo Game Research Station.
    Elmberg, Johan
    Department of Animal Ecology, Swedish University of Agricultural Sciences, Umeå.
    Nummi, Petri
    Department of Applied Zoology, University of Helsinki.
    Sjöberg, Kjell
    Department of Animal Ecology, Swedish University of Agricultural Sciences, Umeå.
    Are ecomorphological associations among dabbling ducks consistent at different spatial scales?1996In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 76, no 3, p. 608-612Article in journal (Refereed)
  • 222.
    Pöysä, Hannu
    et al.
    Evo Game Research Station, Finnish Game and Fisheries Research Institute.
    Elmberg, Johan
    Department of Animal Ecology, Swedish University of Agricultural Sciences, Umeå.
    Nummi, Petri
    Department of Applied Zoology, University of Helsinki.
    Sjöberg, Kjell
    Department of Animal Ecology, Swedish University of Agricultural Sciences, Umeå.
    Species composition of dabbling duck assemblages: ecomorphological patterns compared with null models1994In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 98, no 2, p. 193-200Article in journal (Refereed)
    Abstract [en]

    Ecomorphological patterns of breeding dabbling duck (Anas spp.) assemblages were studied in six regions in northern Europe. Observed spacings among species in terms of bill lamellar density and body length were compared with expected spacings based on null models incorporating different levels of constraints (regional species pools, species relative abundances, lake size and habitat requirements of species). Deviations of observed spacings from expected ones were compared with prey abundance and prey size diversity in the lakes. Observed spacings in terms of body length, but not in terms of bill lamellar density, were greater than expected on the basis of null models. The most abundant species were generally relatively more different than less abundant species in terms of body length but not in terms of bill lamellar density. Deviations between observed and expected spacings in terms of body length were more like those predicted by the competition hypothesis in lakes with low food abundance than in lakes with high food abundance. Patterns in bill lamellar spacings were not related to food abundance nor to food size diversity. In general, patterns in body length spacings were consistent with the competition hypothesis whether the null model used in comparisons was constrained or not.

  • 223.
    Pöysä, Hannu
    et al.
    Finland.
    Elmberg, Johan
    SLU.
    Sjöberg, Kjell
    SLU.
    Nummi, Petri
    Finland.
    Habitat selection and distribution of breeding mallards: what do they reveal about population limitation?2000Conference paper (Refereed)
    Abstract [en]

    The distribution of individuals among habitats and habitat-specific breeding output are basic elements for understanding population limitation and regulation. We studied the connection between habitat selection and population limitation in breeding mallards on boreal lakes in Sweden and Finland with experimental and long-term observational data. Wingclipped mallards were introduced on breeding lakes before migratory wild mallards arrived to test 2 alternative hypotheses of habitat selection, namely ideal preemption and conspecific attraction. The ideal preemptive rule was rejected while the conspecific attraction rule was to some extent supported. However, by combining the results of the introduction experiment with those from an experiment done with mallard ducklings to measure habitat quality, we found that only good-quality lakes attracted wild mallards, whereas poor-quality lakes did not. Long-term observational data from 35 lakes, classified into rich and poor based on shore vegetation, revealed that breeding pairs prefer rich lakes over poor, breeding success also being better there than on the poor lakes. In accordance with the experimental findings, density on the rich lakes increased with overall population density while that on the poor did not. However, breeding success did not show clear density dependence. Our results indicate habitat-specific limitation of breeding numbers, though this may not translate to limitation at the population level.

  • 224.
    Pöysä, Hannu
    et al.
    Finnish Game and Fisheries Research Institute, Evo Game Research Station.
    Elmberg, Johan
    Department of Animal Ecology, Swedish University of Agricultural Sciences, Umeå.
    Sjöberg, Kjell
    Department of Animal Ecology, Swedish University of Agricultural Sciences, Umeå.
    Nummi, Petri
    Department of Applied Zoology, University of Helsinki.
    Habitat selection rules in breeding mallards (Anas platyrhynchos): a test of two competing hypotheses1998In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 114, no 2, p. 283-287Article in journal (Refereed)
    Abstract [en]

    Ideal preemption and conspecific attraction are alternative hypotheses of the habitat selection rules used by individuals. According to the former an occupied site is assumed to be preempted and therefore not available for later arriving individuals, whereas according to the latter individuals are assumed to be attracted by conspecifics to occupied sites, rather than avoiding them. We studied these competing hypotheses in breeding mallards (Anas platyrhynchos) by a cross-over experiment in 2 years, introducing birds onto lakes before migratory wild mallards arrived. If mallards use the ideal preemptive rule, breeding density of wild mallards in experimental lakes should be lower and they should be occupied less frequently than control lakes, but if mallards use the conspecific attraction rule the reverse should be true. Our results allowed us to reject the ideal preemptive rule whereas the conspecific attraction rule was to some extent supported. We discuss these findings in relation to population limitation. The results suggest that the local breeding population studied is not limited by spacing behaviour related to habitat selection.

  • 225.
    Pöysä, Hannu
    et al.
    Finnish Game and Fisheries Research Institute, Evo Game Research Station.
    Elmberg, Johan
    Department of Animal Ecology, Swedish University of Agricultural Sciences, Umeå.
    Sjöberg, Kjell
    Department of Animal Ecology, Swedish University of Agricultural Sciences, Umeå.
    Nummi, Petri
    Department of Applied Zoology, University of Helsinki.
    Nesting mallards (Anas platyrhynchos) forecast brood-stage food limitation when selecting habitat: experimental evidence2000In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 122, no 4, p. 582-586Article in journal (Refereed)
    Abstract [en]

    By combining and reanalysing data from two independent field experiments we explore whether food limitation at the brood stage affects habitat selection in nesting mallards (Anas platyrhynchos). In an introduction experiment we found that, independent of treatment, some study lakes remained empty of wild mallard pairs ("empty lakes"), whereas on other lakes introduced birds attracted wild mallards ("attractive lakes"). In the other experiment we used mallard ducklings to address brood-stage food limitation by studying mass change of ducklings, We found that ducklings foraging on lakes that did not attract wild mallard pairs in the introduction experiment gained much less mass than those foraging on attractive lakes. In most cases ducklings even lost mass in the empty-lake foraging trials, providing strong evidence for food limitation. Therefore. lakes that remained empty of wild mallard pairs in the introduction experiment proved to be inferior brood habitats, particularly in terms of food. Our results give insight into the mechanisms underlying the general habitat selection hypotheses, specifically the ideal preemptive and conspecific attraction rules. The results further support our earlier conclusion that mallards do not use the ideal preemptive rule when selecting nesting lakes. However, conspecific attraction may not be generally applicable either, because. independent of the presence of introduced conspecifics, wild mallards somehow anticipated the low quality of the empty lakes as brood-rearing habitats and made their habitat-selection decision accordingly.

  • 226. Pöysä, Hannu
    et al.
    Nummi, Petri
    Elmberg, Johan
    Kristianstad University, School of Education and Environment.
    Gunnarsson, Gunnar
    Kristianstad University, School of Teacher Education.
    Sjöberg, Kjell
    Mitä kokeellinen tutkimus kertoo sinisorsakantojen säätelymekanismesta: pullonkaulana poikuevaihe?2010In: Suomen Riista, ISSN 0355-0656, Vol. 56, p. 7-15Article in journal (Refereed)
  • 227.
    Pöysä, Hannu
    et al.
    Finnish Game and Fisheries Research Institute, Evo Game Research Station.
    Sjöberg, Kjell
    Department of Animal Ecology, Swedish University of Agricultural Sciences, Umeå.
    Elmberg, Johan
    Kristianstad University, Department of Mathematics and Science.
    Nummi, Petri
    Department of Applied Zoology, University of Helsinki.
    Pair formation among experimentally introduced mallards Anas platyrhynchos reflects habitat quality2001In: Annales Zoologici Fennici, ISSN 0003-455X, E-ISSN 1797-2450, Vol. 38, no 2, p. 179-184Article in journal (Refereed)
    Abstract [en]

    Using data from two independent field experiments, we address whether pair formation in introduced mallards Anas platyrhynchos is associated with habitat quality, specifically food limitation at the brood stage. Based on the concentration of total phosphorous in the water, the study lakes were divided into two groups, 'poor' and 'rich'. In one of the experiments we used mallard ducklings imprinted on humans to study mass change of ducklings in poor and rich lakes, respectively. It turned out that ducklings foraging on poor lakes gained less mass than ducklings foraging on rich lakes, the division of lakes thus reflecting habitat quality at the brood stage. Introduced mallards formed heterosexual pairs on lakes that were, in a relative sense, high-quality brood habitats, whereas they did not on lakes of low-quality brood habitat. Pair formation thus seemed to reflect the suitability of habitat for breeding.

  • 228.
    Ranta, Esa
    et al.
    Integrative Ecology Unit, Department of Zoology, University of Helsinki.
    Laurila, Anssi
    Integrative Ecology Unit, Department of Zoology, University of Helsinki.
    Elmberg, Johan
    Department of Animal Ecology, Swedish University of Agricultural Sciences, Umeå.
    Reinventing the wheel: analysis of sexual dimorphism in body size1994In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 70, no 3, p. 313-321Article in journal (Refereed)
    Abstract [en]

    Sexual dimorphism in body size has received increasing scientific interest during the past decade. In most of the papers on the subject, the magnitude of sexual size dimorphism is expressed as some conversion of body size ratio. There are several possible flaws in using such ratios, however, the most serious one concers the scaling of body size and size differences between sexes. Using ratios may easily lead to wrong conclusions. In this paper we emphasize some fallacies related to ratios and present a less biased method, based on residuals of linear regression. This method is suggested to be used in comparative analyses of sexual size dimorphism.

  • 229.
    Rasmussen, Arne
    et al.
    The Royal Danish Academy of Fine Arts, School of Conservation, Copenhagen.
    Elmberg, Johan
    Kristianstad University, School of Education and Environment.
    "Head for my tail": a new hypothesis to explain how venomous sea snakes avoid becoming prey2009In: Marine Ecolocy, ISSN 0173-9565, E-ISSN 1439-0485, Vol. 30, no 4, p. 385-390Article in journal (Refereed)
    Abstract [en]

    Sea snakes are widespread and conspicuous inhabitants of shallow waters in the Indian and Pacific Oceans. They are agile top predators and possess extremely potent venom, but they are still susceptible to predation by large fish, e.g. sharks, and other vertebrates. We describe how crevice-probing and temporarily non-vigilant Yellow-lipped Sea Kraits Laticauda colubrina twist the tail around their length axis so that the tail tip's lateral aspect corresponds to the dorsal view of the head. In doing so, coloration and pattern in combination with tail movement and posture make the tail appear very similar to the (non-visible and foraging) head. We examined 98 Laticauda spp. sea snakes in three major museum collections and reviewed the literature to assess the generality and implications of our field observations. This leads us to hypothesize that a combination of: (i) head and tail being similarly coloured and patterned, and (ii) the tail being motioned to resemble the head, is a hitherto overlooked mimetic and 'prophylactic' anti-predator adaptation in the L. colubrina complex, and possibly in other species of sea snake. We propose this is a concerted behavioural–morphological adaptation, and we briefly speculate about its possible fitness trade-offs as well as its origin. Explicit and testable predictions derived from the hypothesis are presented.

  • 230.
    Rasmussen, Arne R.
    et al.
    The Royal Danish Academy of Fine Arts, Schools of Architecture, Design and Conservation, Copenhagen.
    Elmberg, Johan
    Kristianstad University, School of Education and Environment.
    Sanders, Kate L.
    School of Earth and Environmental Sciences, University of Adelaide.
    Gravlund, Peter
    Natural History Museum, University of Copenhagen.
    Rediscovery of the rare sea snake Hydrophis parviceps Smith 1935: identification and conservation status2012In: Copeia, ISSN 0045-8511, E-ISSN 1938-5110, no 2, p. 276-282Article in journal (Refereed)
    Abstract [en]

    Smith's small-headed sea snake, Hydrophis parviceps, was originally described in 1935 from a single type specimen collected in southern Vietnam. Since this time there has been only one further record for the species—a specimen collected near the type locality in 1960 that has since been lost. Through field surveys in southern Vietnam in 2001, we obtained three additional specimens of this poorly known sea snake from fisheries bycatch. In the current paper, we present morphological and molecular data for the three new specimens and the holotype, and redescribe H. parviceps based on data synthesized for all five specimens known to date. We also discuss the conservation status of the species based on its vulnerability to fisheries bycatch mortality and seemingly low abundance within a very restricted geographic distribution.

  • 231.
    Rasmussen, Arne R.
    et al.
    The Royal Danish Academy of Fine Arts, School of Conservation, Copenhagen.
    Ineich, Ivan
    Muséum national d'Histoire naturelle, Département de Systématique et Evolution, UMR CNRS 7205 (Origine, Structure et Evolution de la Biodiversité), CP 30 (Reptiles), Paris.
    Elmberg, Johan
    Kristianstad University, School of Education and Environment.
    McCarthy, Colin
    Natural History Museum, London.
    Status of the Asiatic sea snakes of the Hydrophis nigrocinctus group (H. nigrocinctus, H. hendersoni, and H. walli; Elapidae, Hydrophiinae)2011In: Amphibia-Reptilia, ISSN 0173-5373, E-ISSN 1568-5381, Vol. 32, no 4, p. 459-464Article in journal (Refereed)
    Abstract [en]

    The literature of the Hydrophis nigrocinctus group, including Hydrophis nigrocinctus, H. hendersoni and H. walli, is reviewed. Based on internal and external morphological data from the literature and own examination of museum specimens, we recognize two valid species in the complex: Hydrophis nigrocinctus and H. hendersoni. Hydrophis walli is synonymised with H. nigrocinctus.

  • 232.
    Redsted Rasmussen, Arne
    et al.
    The Royal Danish Academy of Fine Arts, School of Conservation, Copenhagen.
    Elmberg, Johan
    Kristianstad University, School of Education and Environment.
    Gravlund, Peter
    Natural History Museum, University of Copenhagen.
    Ineich, Ivan
    Muséum national d’Histoire naturelle, Département de Systématique et Evolution, Paris.
    Sea snakes (Serpentes subfamilies Hydrophiinae and Laticaudinae) in Vietnam: a comprehensive checklist and an updated identification key2011In: Zootaxa, ISSN 1175-5326, E-ISSN 1175-5334, no 2894, p. 1-20Article in journal (Refereed)
    Abstract [en]

    Sea snakes (Elapidae, subfamilies Hydrophiinae and Laticaudinae) reach a very high species richness in Southeast Asia, but most countries in the region still lack comprehensive and up-to-date identification tools for these snakes. We present an updated checklist of sea snakes in Vietnam. We also provide diagnostic characters for all species and a new complete identification key, chiefly based on easy-to-use external characters. The checklist and key cover the 25 species documented from Vietnam, as well as three likely future additions to its sea snake fauna. By surveying incoming fishing vessels between Nha Trang and the mouth of Mekong River in 2000-2001, we were able to document two species new for Vietnamese waters: Hydrophis belcheri and H. pachycercos. Through these surveys we also secured four specimens of the rare endemic species H. parviceps, formerly known only from two specimens. A comprehensive bibliography of the literature treating sea snakes in Vietnamese waters is provided.

  • 233.
    Sanders, Kate L.
    et al.
    School of Earth and Environmental Sciences, University of Adelaide, South Australia, Australia.
    Rasmussen, Arne R.
    The Royal Danish Academy of Fine Arts, Schools of Architecture, Design and Conservation, Copenhagen.
    Elmberg, Johan
    Kristianstad University, School of Education and Environment.
    Independent innovation in the evolution of paddle-shaped tails in viviparous sea snakes (Elapidae Hydrophiinae)2012In: Integrative and Comparative Biology, ISSN 1540-7063, E-ISSN 1557-7023, Vol. 52, no 2, p. 311-320Article in journal (Refereed)
    Abstract [en]

    The viviparous sea snakes (Hydrophiinae) comprise ∼90% of living marine reptiles and display many physical and behavioral adaptations for breathing, diving, and achieving osmotic balance in marine habitats. Among the most important innovations found in marine snakes are their paddle-shaped (dorsoventrally expanded) tails, which provide propulsive thrust in the dense aquatic medium. Here, we reconstruct the evolution of caudal paddles in viviparous sea snakes using a dated molecular phylogeny for all major lineages and computed tomography of internal osteological structures. Bayesian ancestral state reconstructions show that extremely large caudal paddles supported by elongated vertebral processes are unlikely to have been present in the most recent common ancestor of extant sea snakes. Instead, these characters appear to have been acquired independently in two highly marine lineages of relatively recent origin. Both the Aipysurus and Hydrophis lineages have elongated neural spines that support the dorsal edge of their large paddles. However, whereas in the Aipysurus lineage the ventral edge of the paddle is supported by elongated haemapophyses, this support is provided by elongated and ventrally directed pleurapophyses in the Hydrophis lineage. Three semi-marine lineages (Hydrelaps, Ephalophis, and Parahydrophis) form the sister group to the Hydrophis clade and have small paddles with poorly developed dorsal and ventral supports, consistent with their amphibious lifestyle. Overall, our results suggest that not only are the viviparous hydrophiines the only lineage of marine snakes to have acquired extremely large, skeletally supported caudal paddles but also that this innovation has occurred twice in the group in the past ∼2–6 million years.

  • 234.
    Sanders, Kate L.
    et al.
    School of Earth and Environmental Sciences, University of Adelaide.
    Rasmussen, Arne R.
    The Royal Danish Academy of Fine Arts, Schools of Architecture, Design and Conservation, Copenhagen.
    Elmberg, Johan
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap. Kristianstad University, Forskningsmiljön Man and Biosphere Health (MABH).
    Mumpuni, Sancoyo
    Museum Zoologi Bogor, Puslit Biologi-LIPI, Cibinong, Indonesia.
    Guinea, Michael
    School of Science and Primary Industries, Charles Darwin University, Darwin.
    Blias, Peter
    Earth Sciences Section, South Australian Museum, North Terrace, Adelaide.
    Lee, Michael S.Y.
    Earth Sciences Section, South Australian Museum, North Terrace, Adelaide.
    Fry, Bryan G.
    School of Biological Sciences, University of Queensland, Brisbane.
    Aipysurus mosaicus, a new species of egg-eating sea snake (Elapidae: Hydrophiinae), with a redescription of Aipysurus eydouxii (Gray, 1849)2012In: Zootaxa, ISSN 1175-5326, E-ISSN 1175-5334, no 3431, p. 1-18Article in journal (Refereed)
    Abstract [en]

    We describe a new species of egg-eating sea snake, Aipysurus mosaicus sp. nov., from northern Australia and southern New Guinea. This species was previously considered to be an allopatric population of A. eydouxii, which occurs throughout the Sunda Shelf and in New Guinea. Molecular analyses reveal these two species to be sister lineages with fixed nucleotide substitutions at three independent mitochondrial and nuclear loci, and a deep phylogenetic divergence exceeding that of all other sampled species pairs in Aipysurus. Aipysurus mosaicus sp. nov. is also distinguished from A. eydouxii by morphological characters relating to scalation (e.g. number of ventral scales), colour pattern (e.g. number and shape of transverse body bands), internal soft anatomy (e.g. position of heart in relation to ventral scales), and skeletal morphology (e.g. shape of nasal and caudal neural spines). Additional sampling is needed to clarify the extent of geographic contact between A. eydouxii and the new species in New Guinea where they appear to be sympatric. It is likely that the boundaries between these taxa will be mirrored in other coastal sea snakes with ranges spanning the deep waters of the Timor Trench; discovery of such cryptic species will have important implications for conservation of this highly diverse but relatively poorly studied group of marine vertebrates.

  • 235.
    Sanders, Kate L.
    et al.
    School of Earth and Environmental Sciences, University of Adelaide.
    Rasmussen, Arne R.
    The Royal Danish Academy of Fine Arts, Schools of Architecture, Design and Conservation, Copenhagen.
    Mumpuni,
    Museum Zoologi Bogor, Puslit Biologi-LIPI, Cibinong, Indonesia.
    Elmberg, Johan
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap. Kristianstad University, Forskningsmiljön Man and Biosphere Health (MABH).
    de Silva, Anslem
    Gampola, Sri Lanka.
    Guinea, Michael L.
    School of Science and Primary Industries, Charles Darwin University, Darwin.
    Lee, Michael S. Y.
    School of Earth and Environmental Sciences, University of Adelaide.
    Recent rapid speciation and ecomorph divergence in Indo-Australian sea snakes2013In: Molecular Ecology, ISSN 0962-1083, E-ISSN 1365-294X, Vol. 22, no 10, p. 2742-2759Article in journal (Refereed)
    Abstract [en]

    The viviparous sea snakes (Hydrophiinae) are a young radiation of at least 62 species that display spectacular morphological diversity and high levels of local sympatry. To shed light on the mechanisms underlying sea snake diversification, we investigated recent speciation and eco-morphological differentiation in a clade of four nominal species with overlapping ranges in Southeast Asia and Australia. Analyses of morphology and stomach contents identified the presence of two distinct ecomorphs: a ‘macrocephalic’ ecomorph that reaches >2 m in length, has a large head and feeds on crevice-dwelling eels and gobies; and a ‘microcephalic’ ecomorph that rarely exceeds 1 m in length, has a small head and narrow fore-body and hunts snake eels in burrows. Mitochondrial sequences show a lack of reciprocal monophyly between ecomorphs and among putative species. However, individual assignment based on newly developed microsatellites separated co-distributed specimens into four significantly differentiated clusters corresponding to morphological species designations, indicating limited recent gene flow and progress towards speciation. A coalescent species tree (based on mitochondrial and nuclear sequences) and isolation-migration model (mitochondrial and microsatellite markers) suggest between one and three transitions between ecomorphs within the last approximately 1.2 million to approximately 840 000 years. In particular, the macrocephalic ‘eastern’ population of Hydrophis cyanocinctus and microcephalic H. melanocephalus appear to have diverged very recently and rapidly, resulting in major phenotypic differences and restriction of gene flow in sympatry. These results highlight the viviparous sea snakes as a promising system for speciation studies in the marine environment.

  • 236.
    Sjöberg, Kjell
    et al.
    SLU.
    Elmberg, Johan
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap. SLU.
    Pöysä, Hannu
    Finland.
    Nummi, Petri
    Finland.
    Andungar i forskningens tjänst2000In: Svensk jakt, ISSN 0039-6583, Vol. 138, no 5, p. 80-82Article in journal (Other (popular science, discussion, etc.))
  • 237.
    Sjöberg, Kjell
    et al.
    Umeå University.
    Gunnarsson, Gunnar
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap.
    Elmberg, Johan
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap.
    Nummi, Petri
    Finland.
    Pöysä, Hannu
    Finland.
    Density dependent survival of mallard ducklings in boreal lakes: a field experiment2003Conference paper (Refereed)
    Abstract [en]

    From earlier field studies and experiments we have found that the nutrient status of lakes in the boreal region of northern Europe might influence the production of ducklings among dabbling ducks. For ducks, this might be important in the choice of breeding strategy. In this study we created a 2-year cross-over field experiment in northern Sweden where mallard hens and broods (10 ducklings) were introduced on 10 oligotrophic lakes (i.e. poor lakes) in two different densities; 4 hens with broods (high density) on 5 lakes and 1 hen with brood (low density) on the remaining 5 lakes. The adult ducks were wild birds, caught and brought to a game farm where they hatched their eggs. Within a few days after hatching they were released on the lakes in the beginning of June when wild mallards have their hatching peak. After introductions the survival of broods, ducklings and hens were monitored daily the first 12 days and then every third day until day 24. The second year there was a switch of treatments in the lakes. The results after one year indicate that the survival rates of broods, ducklings and hens are density dependent. In lakes with high densities of introduced mallards the survival rates was higher compared to low density lakes.

  • 238.
    Sjöberg, Kjell
    et al.
    SLU.
    Gunnarsson, Gunnar
    Kristianstad University, Research environment Man & Biosphere Health (MABH). Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap.
    Elmberg, Johan
    Kristianstad University, Research environment Man & Biosphere Health (MABH). Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap.
    Nummi, Petri
    Finland.
    Pöysä, Hannu
    Finland.
    Experimentally manipulating early and late breeding in mallards2006Conference paper (Refereed)
    Abstract [en]

    We used imprinted ducklings and wing-clipped female mallards with broods as a complement to observational field studies. Because mallard ducklings search for food by themselves, the food searching efficiency and behaviour of imprinted ducklings and ducklings together with a wing-clipped female ought to reflect the general conditions in the lake they search for food, if not in a strict quantitative way, at least it should reflect the relative differences in conditions for the lakes used in the experiments. We were interested in why mallards start breeding so early and how climate change might influence early and late breeding ducks. In a cross over experiment conducted 2004 and 2005, we studied the result of releasing two sets of female mallards with ducklings. The first one was done close to the same time as wild mallards normally started their breeding season in the region. The other set of broods was delayed 12 days. The eggs for the late release of ducklings were kept at low temperature and 12 days later they were put under sitting mallard females. The hens and broods were subsequently released with an interval of 12 days (one brood in each of 10 lakes in the first release, and the late release in ten other lakes). The next year the lakes were reversed. Survival of ducklings was followed every day during the first 12 days, and later every 4 days up till 24 days. Invertebrates in the lakes were sampled as well (of both benthic and pelagic origins). The data are analyzed in relation to food abundance during the early and late part of the two breeding seasons.

  • 239.
    Sjöberg, Kjell
    et al.
    Department of Wildlife, Fish, and Environmental Studies, Swedish University of Agricultural Sciences, Umeå.
    Gunnarsson, Gunnar
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap. Kristianstad University, Forskningsmiljön Man and Biosphere Health (MABH).
    Pöysä, Hannu
    Finnish Game and Fisheries Research Institute, Joensuu Game and Fisheries Research.
    Elmberg, Johan
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap. Kristianstad University, Forskningsmiljön Man and Biosphere Health (MABH).
    Nummi, Petri
    Department of Forest Sciences, University of Helsinki.
    Born to cope with climate change?: experimentally manipulated hatching time does not affect duckling survival in the mallard Anas platyrhynchos2011In: European Journal of Wildlife Research, ISSN 1612-4642, E-ISSN 1439-0574, Vol. 57, no 3, p. 505-516Article in journal (Refereed)
    Abstract [en]

    Two main hypotheses proposed to explain the seasonal decline in reproductive performance in birds are (1) deterioration of environmental conditions and (2) lower parental quality of late breeders. Previous experimental work addressing these hypotheses generally have problematic biases pertaining to delay of hatching, costs of re-laying and incubation, as well as variation in the quality of eggs, territories, offspring and parental traits. We address these biases in an experimental test of the timing hypothesis (i.e. (1) above) in a precocial bird. Using a 2-year cross-over design and game-farm mallard (Anas platyrhynchos) eggs originating from a number of hens and a standardised delay procedure, we introduced early and late broods with a foster female onto boreal oligotrophic lakes and monitored subsequent duckling survival. Standardised invertebrate sampling was done concurrently to get a measure of lake-level abundance of aquatic prey, a likely causative agent of putative seasonal difference in duckling survival. Survival data and covariates (duckling age; days) were analysed by an information theoretic approach. There was no effect of treatment (i.e. manipulation of hatching date) on duckling survival, which was higher in 2005 than in 2004. In contrast to observational studies from more seasonal wetlands, our experiment demonstrates that duckling survival on boreal lakes was not affected by a 12-day delay in hatching date. Since we did not find any consistent trends in abundance of aquatic prey, i.e. neither clear peaks nor differences between treatment periods, we hypothesise that moderate climate change has minor effects on resource abundance and hence also on mallard duckling survival in boreal environments.

  • 240. Sjöberg, Kjell
    et al.
    Gunnarsson, Gunnar
    Kristianstad University, School of Education and Environment.
    Pöysä, Hannu
    Elmberg, Johan
    Kristianstad University, School of Education and Environment.
    Nummi, Petri
    Experimentally manipulating hatching time in mallards2009Conference paper (Refereed)
  • 241.
    Sjöberg, Kjell
    et al.
    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.
    Nummi, Petri
    Department of Applied Zoology, University of Helsinki.
    Response of Mallard ducklings to variation in habitat quality: an experiment of food limitation2000In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 81, no 2, p. 329-335Article in journal (Refereed)
    Abstract [en]

    Occurrence of Mallard (Anas platyrhynchos) pairs and broods was studied on 86 boreal lakes in two areas in south Finland during 1988-1997 (35 lakes) and 1989-1996 (51 lakes), and field experiments were conducted to determine whether food limitation is an important factor regulating population densities. In general, pairs and broods used and avoided the same lakes, but in both study areas, the proportion of lakes that were unoccupied every year was higher for broods (71% and 69%) than for pairs (26% and 31%). We hypothesized that lakes without breeding Mallards, and especially broods, were too poor to raise young in, and we tested that in field experiments on 22 lakes in boreal Sweden. Based on concentration of total phosphorus in the water, these lakes were divided into two groups: 11 "poor" lakes and 11 "rich" lakes. Mallard ducklings imprinted on humans were used to address brood-stage food limitation by studying mass change. Thirty-one individually marked ducklings were divided into three experimental groups: 12 ducklings were used in poor lakes, 12 ducklings in rich lakes, and 7 ducklings were used as controls receiving no experimental treatment in the field. Each group was studied in 11 daytime trials on 11 different lakes, except the control group which was kept in a pen with free access to food. Ducklings of all groups spent nights together as a big 31-individual group in the same pen and with free access to food. Ducklings foraging on poor lakes gained significantly less body mass than those feeding on rich lakes. At night, when ducklings of both groups had equal and free access to food, ducklings that had been feeding in a poor lake that day gained more mass than those that had been feeding in a rich lake. Overall, similar to 95% of daily mass gain was accounted for by daytime gain in the control group, the corresponding percentage was 35% in the rich-lake experimental group and 11% in the poor-lake experimental group. Thus, we have observational, as well as experimental, evidence to conclude that many boreal lakes are inferior breeding habitat for Mallards, especially during the brood stage. Our results suggest (1) that it is important to recognize at what stage of the yearly reproductive cycle food limitation may occur, (2) that brood stage may be more important than nesting stage for possible population limitation and regulation in breeding Mallards, and (3) that the reason why so many lakes in the boreal region lack breeding Mallards may be food limitation.

  • 242.
    Sjögren, Per
    et al.
    Department of Zoology, Section of Animal Ecology, Uppsala University.
    Elmberg, Johan
    Department of Animal Ecology, Umeå University.
    Berglind, Sven-Åke
    Thermal preference in the pool frog Rana lessonae: impact on the reproductive behaviour of a northern fringe population1988In: Holarctic Ecology, ISSN 0105-9327, Vol. 11, no 3, p. 178-184Article in journal (Refereed)
  • 243.
    Stafford, J
    et al.
    USA.
    Pearse, Aaron
    USA.
    Anteau, M
    USA.
    Janke, E
    USA.
    Eichholz, Mike
    USA.
    Arzel, Céline
    Finland.
    Elmberg, Johan
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap.
    Fox, Tony
    Danmark.
    Straub, J
    USA.
    Spring migration and pre-breeding2013In: 6th North American Duck Symposium: ecology and management of North American waterfowl, 2013, p. 9-Conference paper (Refereed)
  • 244.
    Stafford, Joshua D.
    et al.
    South Dakota State University.
    Janke, Adam K.
    South Dakota State University.
    Anteau, Michael J.
    South Dakota State University.
    Pearse, Aaron T.
    South Dakota State University.
    Fox, Anthony D.
    Aarhus University.
    Elmberg, Johan
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap. Kristianstad University, Research environment Man and Biosphere Health (MABH).
    Straub, Jacob N.
    State University of New York-Plattsburgh.
    Eichholz, Michael W.
    Southern Illinois University Carbondale.
    Arzel, Céline
    University of Turku.
    Spring migration of waterfowl in the northern hemisphere: a conservation perspective2014In: Wildfowl, ISSN 0954-6324, E-ISSN 2052-6458, no Special Issue 4, p. 70-85Article in journal (Refereed)
    Abstract [en]

     Spring migration is a key part of the annual cycle for waterfowl populations in the northern hemisphere, due to its temporal proximity to the breeding season and because resources may be limited at one or more staging sites. Research based on field observations during spring lags behind other periods of the year, despite the potential for fitness consequences through diminished survival or cross-seasonal effects of conditions experienced during migration. Consequently, conservation strategies for waterfowl on spring migration are often only refined versions of practices used during autumn and winter. Here we discuss the current state of knowledge of habitat requirements for waterfowl at their spring migratory sites and the intrinsic and extrinsic factors that lead to variability in those requirements. The provision of plant foods has become the main conservation strategy during spring because of the birds’ energy requirements at this time, not only to fuel migration but to facilitate early clutch formation on arrival at the breeding grounds. Although energy sources are important to migrants, there is little evidence on the extent to which the availability of carbohydrate-based food is limiting for many migratory waterfowl populations. Such limitation is relatively unlikely among populations that exploit agricultural grain during migration (e.g. arctic-nesting geese), suggesting that conservation strategies for these populations may be misplaced. In general, however, we found few cases in which an ecological understanding of spring-migrating waterfowl was sufficient to indicate true resource limitation during migration, and still fewer cases where conservation efforts ameliorated these limitations. We propose a framework that aims to address knowledge gaps and apply empirical research results to conservation strategies based on documented limitations and associated fitness impacts on migrating waterfowl. Such a strategy would improve allocation of scarce conservation resources during spring migration and greatly improve ecological understanding of migratory waterfowl and their habitats in the northern hemisphere.

  • 245.
    Söderquist, Per
    et al.
    Kristianstad University, School of Education and Environment.
    Elmberg, Johan
    Kristianstad University, School of Education and Environment.
    "Hjälp oss kartlägga gräsandens genetik!"2011In: Vår fågelvärld, ISSN 0042-2649, Vol. 70, no 2, p. 40-Article in journal (Other (popular science, discussion, etc.))
  • 246.
    Söderquist, Pär
    et al.
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap.
    Elmberg, Johan
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap. Kristianstad University, Research environment Man & Biosphere Health (MABH).
    Gunnarsson, Gunnar
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap.
    Utsatta änder – så går det för dem2014In: Svensk jakt, ISSN 0039-6583, Vol. 152, no 12, p. 72-73Article in journal (Other (popular science, discussion, etc.))
  • 247.
    Söderquist, Pär
    et al.
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap. Kristianstad University, Research environment Man & Biosphere Health (MABH).
    Elmberg, Johan
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap. Kristianstad University, Research environment Man & Biosphere Health (MABH).
    Gunnarsson, Gunnar
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap. Kristianstad University, Research environment Man & Biosphere Health (MABH).
    Thulin, Carl-Gustaf
    Champagnon, Jocelyn
    Guillemain, Matthieu
    Kreisinger, Jakub
    Prins, Herbert
    Crooijmans, R
    Kraus, Robert
    Released game birds cause introgression in European mallard2015Conference paper (Refereed)
    Abstract [en]

    The practice of restocking already viable populations to improve harvest has since long been common in forestry, fisheries and wildlife management. The potential risks with restocking of native species has for a long time been overshadowed by the related issue of invasive species. However, during the last decade releases of native species with a potential non-native genome have attained more attention. A suitable model species for studying genetic effects of large-scale releases of a native species is the Mallard, Anas platyrhynchos; it is the most widespread duck in the world, it is a migrating species, and an important game bird. In several European countries it is also farmed and released to increase the harvestable population, and more than 3 million unfledged hatchlings are released each year around Europe. The aims of this study were to determine if wild and released farmed Mallards differed genetically among subpopulations in Europe, if there are signs of previous or ongoing introgression between wild and farmed Mallards, and if the genetic structure of the wild Mallard population has changed since large-scale releases started in the 1970s. We used 360 Single Nucleotide Polymorphisms (SNPs) to analyze the genetic structure of historical wild, present-day wild, and farmed Mallards. We found a clear genetic difference between wild and farmed Mallards in Europe. We also found signs of introgression of farmed genes in the wild Mallard population, however, the rate of hybridization is probably minor due to low survival of released farmed Mallards and a change of the wild population since the start of large-scale releases is therefore limited. A low level of hybridization between farmed and wild Mallard is desired as introgressed genes may be detrimental for wild Mallards, and efforts to increase survival of farmed Mallards should therefore not be encouraged.

  • 248.
    Söderquist, Pär
    et al.
    Kristianstad University, Research environment Man & Biosphere Health (MABH). Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap.
    Elmberg, Johan
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap.
    Gunnarsson, Gunnar
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap.
    Thulin, Carl-Gustaf
    SLU, Umeå.
    Champagnon, Jocelyn
    Frankrike.
    Guillemain, Matthieu
    Frankrike.
    Kreisinger, Jakub
    Tjeckien.
    Prins, Herbert
    Nederländerna.
    Crooijmans, Richard
    Nederländerna.
    Kraus, Robert
    Tyskland.
    Released gamebrds cause introgression in European mallard2015In: 4th Pan-European Duck Symposium, Hangö, Finland, 2015, p. 75-Conference paper (Refereed)
    Abstract [en]

    The practice of restocking already viable populations to improve harvest has since long been common in forestry, fisheries and wildlife management. The potential risks with restocking of native species has for a long time been overshadowed by the related issue of invasive species. However, during the last decade releases of native species with a potential non-native genome have attained more attention. A suitable model species for studying genetic effects of large-scale releases of a native species is the Mallard, Anas platyrhynchos; it is the most widespread duck in the world, it is a migrating species, and an important game bird. In several European countries it is also farmed and released to increase the harvestable population, and more than 3 million unfledged hatchlings are released each year around Europe. The aims of this study were to determine if wild and released farmed Mallards differed genetically among subpopulations in Europe, if there are signs of previous or ongoing introgression between wild and farmed Mallards, and if the genetic structure of the wild Mallard population has changed since large-scale releases started in the 1970s. We used 360 Single Nucleotide Polymorphisms (SNPs) to analyze the genetic structure of historical wild, present-day wild, and farmed Mallards. We found a clear genetic difference between wild and farmed Mallards in Europe. We also found signs of introgression of farmed genes in the wild Mallard population, however, the rate of hybridization is probably minor due to low survival of released farmed Mallards and a change of the wild population since the start of large-scale releases is therefore limited. A low level of hybridization between farmed and wild Mallard is desired as introgressed genes may be detrimental for wild Mallards, and efforts to increase survival of farmed Mallards should therefore not be encouraged.

  • 249.
    Söderquist, Pär
    et al.
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap.
    Elmberg, Johan
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap. Kristianstad University, Research environment Man & Biosphere Health (MABH).
    Gunnarsson, Gunnar
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap.
    Thulin, C.-G.
    Champagnon, Jocelyn
    Guillemain, Matthieu
    Kreisinger, J.
    Prins, H
    Crooijmans, R.
    Kraus, R.
    Released game birds cause continent-wide introgression: a changing genetic landscape in European mallard (Anas platyrhynchos)Manuscript (preprint) (Other academic)
  • 250.
    Söderquist, Pär
    et al.
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap. Kristianstad University, Forskningsmiljön Man and Biosphere Health (MABH).
    Gunnarsson, Gunnar
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap. Kristianstad University, Forskningsmiljön Man and Biosphere Health (MABH).
    Elmberg, Johan
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap. Kristianstad University, Forskningsmiljön Man and Biosphere Health (MABH).
    Longevity and migration distance differ between wild and hand-reared mallards Anas platyrhynchos in Northern Europe2013In: European Journal of Wildlife Research, ISSN 1612-4642, E-ISSN 1439-0574, Vol. 59, no 2, p. 150-166Article in journal (Refereed)
    Abstract [en]

    The mallard Anas platyrhynchos is the world’s most widespread and numerous dabbling duck. It is also farmed and released to the wild by the millions each year, but the effects of this on wild populations remain little studied. By using historical national ringing–recovery data from Sweden and Finland, we here address three predictions based on previous studies: (1) longevity is higher in wild than in hand-reared mallards, (2) wild mallards migrate longer than hand-reared, and (3) migration distance in wild ducks surviving long enough to start fall migration has decreased over the last 50 years. Indeed, wild mallards lived longer than hand-reared (19 versus 9 months in Swedish birds and 13 versus 4 months in Finnish birds). Compared to wild mallards, a smaller proportion of hand-reared birds survived long enough to have the chance to enter the wild breeding population; less than 25 % of the Swedish birds and less than 10 % of the Finnish birds lived a year or longer. Wild birds migrated farther than hand-reared (mean distance in Swedish birds, 676 versus 523 km; in Finnish birds, 1,213 versus 157 km), a pattern caused by both shorter life span and lower migration speed in hand-reared birds. Mean migration distance in wild Swedish mallards was 787 km in 1947–1972 but 591 km in 1977–1993. This difference was not statistically significant, though, possibly due to the limited sample size and lack of data from the last two decades. In general, our study provides a conservative test of the predictions addressed, calling for more research about the consequences of restocking duck populations.

23456 201 - 250 of 257
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