| 1. |
- Elmberg, Johan, 1960-, et al.
(author)
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Abundance-distribution relationships on interacting trophic levels : the case of lake-nesting waterfowl and dytiscid water beetles
- 2000
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In: Journal of Biogeography. - 0305-0270 .- 1365-2699. - 0305-0270 ; 27:4, s. 821-827
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Journal article (peer-reviewed)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.
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| 2. |
- Elmberg, Johan, et al.
(author)
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Andkonferens på prärien
- 2001
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In: Vår fågelvärld. - 0042-2649. ; 60:8, s. 25-
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Journal article (pop. science, debate, etc.)
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| 3. |
- Elmberg, Johan, et al.
(author)
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Andkonferens på prärien
- 2001
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In: Vår fågelvärld. - 0042-2649. ; 60:8
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Journal article (other academic/artistic)
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| 4. |
- Elmberg, Johan, 1960-, et al.
(author)
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Breeding success of sympatric dabbling ducks in relation to population density and food resources
- 2003
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In: Oikos. - 0030-1299 .- 1600-0706. - 0030-1299 ; 100:2, s. 333-341
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Journal article (peer-reviewed)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.
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| 5. |
- Elmberg, Johan, et al.
(author)
-
Breeding success of sympatric dabbling ducks in relation to population density and food resources
- 2003
-
In: Oikos. - : Wiley-Blackwell Publishing Ltd. - 0030-1299 .- 1600-0706. ; 100:2, s. 333-341
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Journal article (peer-reviewed)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 thenbetween 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.
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| 6. |
- Elmberg, Johan, et al.
(author)
-
Density dependent breeding success in mallards
- 2003
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Conference paper (peer-reviewed)abstract
- Breeding success in wild mallards was studied on small eutrophic nemoral lakes in a two-year cross-over experiment in which wing-clipped conspecifics were added to increase pair density. The number of wild mallards that came to the lakes to nest (prior to introductions) did not differ between years. Introduction treatment led to a significant reduction in brood number in wild mallards, but it did not alter the number of stage 2+ ducklings finally produced on a lake. Introduction had no effect on lake utilization by broods, ducklings and non-breeding adults (cumulative days over the entire breeding season). Abundance of invertebrate prey differed greatly among lakes, but it did not correlate with breeding success. Breeding success was thus subject to sequential density-dependence; i.e. a lower number of broods still produced the same number of 2+ ducklings. We speculate that predation is the most likely process behind both patterns. We conclude that late and snapshot measures of duckling productivity may mask density dependent population processes of fundamental importance to regulation and harvest policy.
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| 7. |
- Elmberg, Johan, et al.
(author)
-
Density dependent breeding success in mallards
- 2003
-
Conference paper (other academic/artistic)abstract
- Breeding success in wild mallards was studied on small eutrophic nemoral lakes in a two-year cross-over experiment in which wing-clipped conspecifics were added to increase pair density. The number of wild mallards that came to the lakes to nest (prior to introductions) did not differ between years. Introduction treatment led to a significant reduction in brood number in wild mallards, but it did not alter the number of stage 2+ ducklings finally produced on a lake. Introduction had no effect on lake utilization by broods, ducklings and non-breeding adults (cumulative days over the entire breeding season). Abundance of invertebrate prey differed greatly among lakes, but it did not correlate with breeding success. Breeding success was thus subject to sequential density-dependence; i.e. a lower number of broods still produced the same number of 2+ ducklings. We speculate that predation is the most likely process behind both patterns. We conclude that late and snapshot measures of duckling productivity may mask density dependent population processes of fundamental importance to regulation and harvest policy.
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| 8. |
- Elmberg, Johan, 1960-, et al.
(author)
-
Farligt att vara andägg
- 2002
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In: Svensk jakt. - 0039-6583. ; 140:10, s. 18-20
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Journal article (pop. science, debate, etc.)
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| 9. |
- Elmberg, Johan, et al.
(author)
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Farligt att vara andägg
- 2002
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In: Svensk jakt. - 0039-6583. ; 140:10, s. 18-20
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Journal article (other academic/artistic)
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| 10. |
- Elmberg, Johan, 1960-, et al.
(author)
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Hur många får ligga i orubbat bo?
- 2003
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In: Vår fågelvärld. - 0042-2649. ; :3, s. 28-29
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Journal article (pop. science, debate, etc.)
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