| 1. |
- Arzel, Céline, et al.
(författare)
-
Does changing spring phenology affect short and long distance migratory waterfowl similarly?
- 2010
-
Ingår i: The abstract book. ; , s. 43-
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Among waterfowl, most ducks may be considered income breeders due to their small body size and their limited capacity to store energy. Therefore limited access to resources on their breeding grounds is likely to affect their breeding schedule and potentially output. At northern latitudes, ice break up dictates the access to the breeding lakes. An early ice break up allows for early access to the breeding site and its feeding resources, and potentially leading to higher breeding output than after a late ice break up. Short distance migrants are thus more likely to adapt to ice break up conditions than long distance migrants which have to cope with weather conditions en route and local resource accessibility along the migratory path. Using 20 years of data on breeding phenology and success of 3 species of ducks differing in their migratory strategy - Teal Anas crecca, Mallard Anas platyrhynchos and Common Goldeneye Bucephala clangula - in a watershed in Finland, we test the idea that variation in spring phenology affects the reproductive performance of duck species differently depending on their migration pattern.
|
|
| 2. |
- Dessborn, Lisa, 1976-, et al.
(författare)
-
Hatching in dabbling ducks and emergence in chironomids : a case of predator-prey synchrony?
- 2009
-
Ingår i: Hydrobiologia. - : Springer Verlag (Germany). - 0018-8158 .- 1573-5117. - 0018-8158 ; 636:1, s. 319-329
-
Tidskriftsartikel (refereegranskat)abstract
- It has been hypothesized that dabbling ducks (Anas spp.) time breeding to coincide with annual regional peaks in emerging dipterans, especially Chironomidae, which are important prey for newly hatched ducklings. However, this hypothesis has never been evaluated in a replicated lake-level study, including year effects in emergence patterns. We collected duck and invertebrate data from 12 lakes during the nesting seasons 1989-1994 in a watershed in southern Finland. The oligotrophic study lakes are typical of the boreal Holarctic, as are the three focal duck species: mallard Anas platyrhynchos L., widgeon Anas penelope L and teal Anas crecca L. Hatching of ducklings showed a clear peak in relation to ambient phenology (annual ice-out date of lakes), whereas chironomid emergence was more erratic and showed no clear peak at the lake level, although total watershed-level emergence was somewhat higher before and long after the duck hatching peak. Thus, we find no evidence that ducklings hatch in synchrony with abundance peaks of emerging chironomids. There was large within-year temporal variation in chironomid emergence among lakes, but this was not correlated with ambient temperature. The rank of individual lakes with respect to the abundance of emerging chironomids was consistent among as well as within years, a predictability that ought to make adaptive lake choice by ducks possible. On the lake level, there was a positive correlation between the total amount of emerging chironomids and brood use. We argue that emergence patterns of chironomids on typical boreal lakes are neither compressed nor predictable enough to be a major selective force on the timing of egg-laying and hatching in dabbling ducks. Despite spatial (among-lake) patterns of abundance of emerging chironomids being predictable within and among years, the observed pattern of brood use suggests that other factors, e.g. habitat structure, also affect lake choice.
|
|
| 3. |
- Elmberg, Johan, 1960-, et al.
(författare)
-
Abundance-distribution relationships on interacting trophic levels : the case of lake-nesting waterfowl and dytiscid water beetles
- 2000
-
Ingår i: Journal of Biogeography. - 0305-0270 .- 1365-2699. - 0305-0270 ; 27:4, s. 821-827
-
Tidskriftsartikel (refereegranskat)abstract
- Aim To compare patterns in local abundance, regional distribution and body size in waterfowl and dytiscid beetles sampled from the same lakes. Location Thirty Swedish lakes, 56-63 degrees N. Methods Birds were censused repeatedly, at which time submerged activity traps were placed on the littoral to catch invertebrates. Avian patterns were analysed separately for four different selections of species, each motivated on functional or phylogenetical grounds. Patterns in dytiscid beetles have been described earlier in Nilsson, Elmberg & Sjoberg (1994). Results Although there were large differences between individual lakes, there was no significant latitudinal gradient at the lake level in either species richness or abundance in any of the bird groupings. Lakes which were rich in species and numbers of dytiscid beetles were also rich in species and numbers of all four waterfowl groups. Three of the four bird groups conform with the general pattern of widely distributed species being more abundant locally, as do dytiscid beetles in the same lakes. Body mass and local abundance were correlated in one of the four birds groups only, i.e. dabbling ducks, (Anas spp.). Main conclusions We find evidence for a similar and positive local abundance-distribution relationship in dytiscid beetles and waterfowl breeding in the same lakes, but no common general pattern in local abundance vs. body size.
|
|
| 4. |
- Elmberg, Johan, 1960-, et al.
(författare)
-
Breeding success of sympatric dabbling ducks in relation to population density and food resources
- 2003
-
Ingår i: Oikos. - 0030-1299 .- 1600-0706. - 0030-1299 ; 100:2, s. 333-341
-
Tidskriftsartikel (refereegranskat)abstract
- Breeding success in sympatric mallard Anas platyrhynchos, teal A. crecca and wigeon A. penelope in a boreal watershed in Finland was studied for 12 years. Benthic and surface-emerging prey animals were trapped to obtain annual indices of food abundance. Mallard and teal were equally abundant over the years, being roughly twice as numerous as wigeon. Pair density, brood:pair ratio and duckling:pair ratio were used to test the hypothesis that per capita breeding success decreases in a density-dependent fashion as either pair density or the number of nesting pairs per available food unit increases. In mallard we found no density-dependent patterns at all. In teal per capita brood production decreased as prey animals became relatively scarcer, but this interpretation may not be robust. In wigeon, however, there were two independent significant patterns of direct density-dependence in a temporal succession, i.e. between pair density and per capita brood production in the early part of the breeding season, and then between per capita abundance of surface-emerging insect prey and the number of ducklings per pair. Despite wide dietary overlap and frequent co-occurrence on single lakes among species in the guild, we found no evidence for interspecific density-dependent effects. We hypothesize that there is no or infrequent food limitation for breeding dabblers in this system, and that behavior may be the process behind the pattern of density-dependence in wigeon.
|
|
| 5. |
- Elmberg, Johan, 1960-, et al.
(författare)
-
Do intruding predators and trap position affect the reliability of catches in activity traps?
- 1992
-
Ingår i: Hydrobiologia. - 0018-8158 .- 1573-5117. - 0018-8158 ; 239:3, s. 187-193
-
Tidskriftsartikel (refereegranskat)abstract
- Forty lakes in Sweden and Finland were sampled in 1990 with activity traps to evaluate the effects of trapped predators on invertebrate catch. Vertebrate (fish, newts) and invertebrate (leeches, dragonflies, water beetles, backswimmers and water scorpions) predators were considered separately. Invertebrate predators affected neither the abundance nor the taxonomic diversity of the catches. Vertebrate predators had no effect on the abundance but reduced the taxonomic diversity of the catches significantly. Thus, vertebrate predators are a possible source of bias in activity trap catches, but oily concerning taxonomic diversity. Within the depth gradient studied (0.25-0.75 m), trap position (suspended in mid-water versus on the bottom) did not affect the percentages of nektonic and benthic invertebrates in the catches. The relative abundance of all taxa was similar in the catches from different trap positions, but the relative abundance of the most numerous taxa as well as the diversity of the catches differed between trap positions. We conclude that both mid-water and bottom traps are suitable for monitoring aquatic invertebrates, and that bottom traps may be preferred for practical reasons.
|
|
| 6. |
- Elmberg, Johan, 1960-, et al.
(författare)
-
Early breeding teal Anas crecca use the best lakes and have the highest reproductive success
- 2005
-
Ingår i: Annales Zoologici Fennici. - 0003-455X .- 1797-2450. ; 42:1, s. 37-43
-
Tidskriftsartikel (refereegranskat)abstract
- Teal (Anas crecca) broods were studied in 1988-2003 in a boreal watershed comprising 51 permanent wetlands. Brood size of near-fledged ducklings was negatively related to the hatching date, i.e. early pairs had higher reproductive success than late pairs. However, brood size of newly hatched ducklings was not related to the hatching date, implying that the advantage of early breeding is due to processes operating during the brood stage rather than during nesting. Half of the lakes never produced a brood, and among the 26 lakes that actually did, two `preferred' lakes generated 44% of the broods and 55% of the near-fledged ducklings. Early broods were over-represented on such `preferred' lakes, and late broods over-represented on `less preferred' lakes. Our study suggests that lake selection and early nesting may have important fitness consequences in teal.
|
|
| 7. |
- Elmberg, Johan, 1960-, et al.
(författare)
-
Factors affecting species number and density of dabbling duck guilds in North Europe
- 1993
-
Ingår i: Ecography. - 0906-7590 .- 1600-0587. - 0906-7590 ; 16:3, s. 251-260
-
Tidskriftsartikel (refereegranskat)abstract
- We addressed how species number and pair density in guilds of co-existing species is related to habitat structure, and to the abundance and diversity of food resources. using the assemblage of seven species of dabbling ducks (genus Anas) breeding in 60 lakes distributed over six regions in temperate north Europe. Partial correlation and multiple regression revealed that species richness was best predicted by habitat structural diversity as indexed by a principal component analysis based on 18 vegetation and lake characteristics, and by the abundance of aquatic and emergent prey. We found no effect of lake size or prey size diversity on species richness. Pair density was correlated with the percentage of shoreline with horsetails (Equisetum), by habitat structural diversity and by the abundance of emergent invertebrate prey. Neither prey size diversity nor abundance of aquatic prey correlated with pair density. Species richness and pair density in North European duck guilds vary both with habitat structure and prey availability.
|
|
| 8. |
|
|
| 9. |
- Elmberg, Johan, 1960-, et al.
(författare)
-
Interspecific interactions and co-existence in dabbling ducks : observations and an experiment
- 1997
-
Ingår i: Oecologia. - 0029-8549 .- 1432-1939. - 0029-8549 ; 111:1, s. 129-136
-
Tidskriftsartikel (refereegranskat)abstract
- We studied the possible role of resource limitation and interspecific competition in assemblages of dabbling ducks on breeding lakes in Finland and Sweden with observational and experimental data. After initial vegetation mapping and yearly censuses of ducks in 1985-1990, we collected observational data in 1991-1994 from 28 lakes with natural populations of mallard Anas platyrhynchos and teal A. crecca. Mallard and teal co-occur over vast areas in the Holarctic and they are the only breeding dabbling ducks on many oligotrophic lakes. Both species are migratory in our study regions, teal arriving later in spring than mallards. Log-linear model analysis of observational presence/absence data revealed a positive, not a negative, association between the species. This association was independent of habitat diversity as well as of lake size. Mallard-teal interaction was also studied in a cross-over introduction experiment in 32 other lakes in two years. Wing-clipped mallards were introduced to breeding lakes before the arrival of teal to induce resource limitation and interspecific competition, hypothesized to reduce lake use by teal. The density of mallard pairs on experimental lakes was 2.9-8.0 times higher than on controls, but there was no negative response by teal to the treatment. This is the first combined observational-experimental demonstration of lack of interspecific competition in waterfowl. Our results indicate that heterospecific attraction may affect species co-existence in dabbling ducks.
|
|
| 10. |
- Elmberg, Johan, 1960-, et al.
(författare)
-
Patterns of lake acidity and waterfowl communities
- 1994
-
Ingår i: Hydrobiologia. - 0018-8158 .- 1573-5117. - 0018-8158 ; 279-280:1, s. 201-206
-
Tidskriftsartikel (refereegranskat)abstract
- Breeding waterfowl communities were studied in 28 lakes in three areas in North Europe, along gradients of acid precipitation and alkalinity that result in lake conditions ranging from unaffected to strongly acidified. Acidic lakes had generally sparser and less complex vegetation, and fewer invertebrates were caught in activity traps. There was neither correlation between pH and waterfowl species richness (genus Anas, family Anatidae, and waterfowl sensu latu tested separately), nor between pH and waterfowl diversity (Simpson's index). Further, pH and waterfowl population density (genus Anas, family Anatidae, and waterfowl sensu latu) were not correlated, but when functional rather than taxonomic groups were considered, pH and relative abundance of fish-eating species (Gaviidae and Podicipedidae) were correlated. However, the relative abundance of Bucephala clangula, a diving duck that may compete with fish for food, was not correlated with pH. Although individual species may be affected, community level responses of waterfowl to acidity are either absent or hard to detect at our sites.
|
|
