| 1. |
- Gunnarsson, Gunnar, et al.
(författare)
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Food limits survival of breeding boreal mallards Anas platyrhynchos
- 2003
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Konferensbidrag (refereegranskat)abstract
- During the breeding period dabbling ducks (Anas sp.), and especially newly hatched ducklings, face heavy mortality. The reasons are not clear, but suggested factors contributing are scarce food, predation, chilling and disease. We highlighted the question why many of the boreal lakes in Scandinavia are without breeding ducks and why mortality is considerable during brood period. In an experimental study in 2002 we hypothesized food being a major factor deciding duck survival during breeding. One wing-clipped hen mallard with her own newly hatched brood (10 ducklings) was introduced onto each of 10 lakes. Food was added ad libitum at 5 of these lakes (experimental lakes), whereas the other five lakes (controls) did not get any extra food added. Survival of hens, broods as well as each individual duckling was monitored regularly until 24 days after introduction. At all three levels (i.e. duckling, brood and adult), survival was significantly higher on lakes with food added than on control lakes, although the difference was most pronounced on the duckling level. Direct consequences (i.e. dying from starvation) as well as indirect (e.g. undernourished individuals being more easily taken by predators) may both explain this pattern. Our results clearly show that food is a major limiting factor on mallard survival in this environment. Also, our results may explain why many boreal lakes in Scandinavia do not have any breeding waterfowl at all. It seems likely that such lakes are too poor to raise broods and even to sustain adults.
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| 2. |
- Gunnarsson, Gunnar, et al.
(författare)
-
Food limits survival of breeding boreal mallards Anas platyrhynchos
- 2003
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- During the breeding period dabbling ducks (Anas sp.), and especially newly hatched ducklings, face heavy mortality. The reasons are not clear, but suggested factors contributing are scarce food, predation, chilling and disease. We highlighted the question why many of the boreal lakes in Scandinavia are without breeding ducks and why mortality is considerable during brood period. In an experimental study in 2002 we hypothesized food being a major factor deciding duck survival during breeding. One wing-clipped hen mallard with her own newly hatched brood (10 ducklings) was introduced onto each of 10 lakes. Food was added ad libitum at 5 of these lakes (experimental lakes), whereas the other five lakes (controls) did not get any extra food added. Survival of hens, broods as well as each individual duckling was monitored regularly until 24 days after introduction. At all three levels (i.e. duckling, brood and adult), survival was significantly higher on lakes with food added than on control lakes, although the difference was most pronounced on the duckling level. Direct consequences (i.e. dying from starvation) as well as indirect (e.g. undernourished individuals being more easily taken by predators) may both explain this pattern. Our results clearly show that food is a major limiting factor on mallard survival in this environment. Also, our results may explain why many boreal lakes in Scandinavia do not have any breeding waterfowl at all. It seems likely that such lakes are too poor to raise broods and even to sustain adults.
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| 3. |
- Elmberg, Johan, 1960-, et al.
(författare)
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Early breeding teal Anas crecca use the best lakes and have the highest reproductive success
- 2005
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Ingår i: Annales Zoologici Fennici. - 0003-455X .- 1797-2450. ; 42:1, s. 37-43
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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.
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| 4. |
- Elmberg, Johan, et al.
(författare)
-
Early breeding teal Anas crecca use the best lakes and have the highest reproductive success
- 2005
-
Ingår i: Annales Zoologici Fennici. - : Finnish Zoological and Botanical Publishing Board. - 0003-455X. ; 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.
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| 5. |
- Gunnarsson, Gunnar, 1976-, et al.
(författare)
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Why are there so many empty lakes? : food limits survival of mallard ducklings
- 2004
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Ingår i: Canadian Journal of Zoology. - 0008-4301 .- 1480-3283. ; 82:11, s. 1698-1703
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Tidskriftsartikel (refereegranskat)abstract
- Food is an important factor affecting survival in many bird species, but this relationship has rarely been explored experimentally with respect to reproductive output of precocial birds. In a field experiment we tested the hypothesis that food abundance limits reproductive output in breeding dabbling ducks. Onto 10 oligotrophic lakes in northern Sweden we introduced one wing-clipped female mallard (Anas platyrhynchos L., 1758) and a brood of 10 newly hatched ducklings, and survival was monitored for 24 days. Food was added ad libitum at five of the lakes, but not at the other five. Duckling survival was best modelled to include a treatment effect, with higher survival on lakes with food added, and a negative effect of harsh weather. As expected, duckling survival increased nonlinearly with age. Only one female remained on control lakes after 24 days, whereas four remained on lakes with food added. This is the first experimental demonstration that food may limit survival and reproductive output in breeding precocial birds. We argue that food limitation may be one reason why duckling mortality is high and why many lakes throughout the Holarctic have no breeding dabbling ducks.
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| 6. |
- Gunnarsson, Gunnar, et al.
(författare)
-
Why are there so many empty lakes? : food limits survival of mallard ducklings
- 2004
-
Ingår i: Canadian Journal of Zoology. - : National Research Council of Canada. - 0008-4301 .- 1480-3283. ; 82:11, s. 1698-1703
-
Tidskriftsartikel (refereegranskat)abstract
- Food is an important factor affecting survival in many bird species, but this relationship has rarely been explored experimentally with respect to reproductive output of precocial birds. In a field experiment we tested the hypothesis that food abundance limits reproductive output in breeding dabbling ducks. Onto 10 oligotrophic lakes in northern Sweden we introduced one wing-clipped female mallard (Anas platyrhynchos L., 1758) and a brood of 10 newly hatched ducklings, and survival was monitored for 24 days. Food was added ad libitum at five of the lakes, but not at the other five. Duckling survival was best modelled to include a treatment effect, with higher survival on lakes with food added, and a negative effect of harsh weather. As expected, duckling survival increased nonlinearly with age. Only one female remained on control lakes after 24 days, whereas four remained on lakes with food added. This is the first experimental demonstration that food may limit survival and reproductive output in breeding precocial birds. We argue that food limitation may be one reason why duckling mortality is high and why many lakes throughout the Holarctic have no breeding dabbling ducks.
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| 7. |
- Sjöberg, Kjell, et al.
(författare)
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Density dependent survival of mallard ducklings in boreal lakes : a field experiment
- 2003
-
Konferensbidrag (refereegranskat)abstract
- 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.
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| 8. |
- Sjöberg, Kjell, et al.
(författare)
-
Density dependent survival of mallard ducklings in boreal lakes : a field experiment
- 2003
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 9. |
- Arzel, Céline, et al.
(författare)
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Early springs and breeding performance in two sympatric duck species with different migration strategies
- 2014
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Ingår i: Ibis. - : Wiley: 12 months. - 0019-1019 .- 1474-919X. ; 156:2, s. 288-298
-
Tidskriftsartikel (refereegranskat)abstract
- The capacity of migratory species to adapt to climate change may depend on their migratory and reproductive strategies. For example, reproductive output is likely to be influenced by how well migration and nesting are timed to temporal patterns of food abundance, or by temperature variations during the brood rearing phase. Based on two decades (1988–2009) of waterfowl counts from a boreal catchment in southern Finland we assessed how variation in ice break-up date affected nesting phenology and breeding success in two sympatric duck species, Mallard Anas platyrhynchos and Eurasian Teal Anas crecca. In Fennoscandia these species have similar breeding habitat requirements but differ in migration distance; Teal migrate roughly seven times as far as do Mallard. Annual ice break-up date was used as a proxy of spring ‘earliness’ to test the potential effect of climate change on hatching timing and breeding performance. Both species were capable of adapting their nesting phenology, and bred earlier in years when spring was early. However, the interval from ice break-up to hatching tended to be longer in early springs in both species, so that broods hatched relatively later than in late springs. Ice break-up date did not appear to influence annual number of broods per pair or annual mean brood size in either species. Our study therefore does not suggest that breeding performance in Teal and Mallard is negatively affected by advancement of ice break-up at the population level. However, both species showed a within-season decline in brood size with increasing interval between ice break-up and hatching. Our study therefore highlights a disparity between individuals in their capacity to adjust to ice break-up date, late breeders having a lower breeding success than early breeders. We speculate that breeding success of both species may therefore decline should a consistent trend towards earlier springs occur.
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| 10. |
- Arzel, Céline, et al.
(författare)
-
Early springs and breeding performance in two sympatric duck species with different migration strategies
- 2014
-
Ingår i: Ibis. - : Wiley-Blackwell Publishing Ltd. - 0019-1019 .- 1474-919X. ; 156:2, s. 288-298
-
Tidskriftsartikel (refereegranskat)abstract
- The capacity of migratory species to adapt to climate change may depend on their migratory and reproductive strategies. For example, reproductive output is likely to be influenced by how well migration and nesting are timed to temporal patterns of food abundance, or by temperature variations during the brood rearing phase. Based on two decades (1988–2009) of waterfowl counts from a boreal catchment in southern Finland we assessed how variation in ice break-up date affected nesting phenology and breeding success in two sympatric duck species, Mallard Anas platyrhynchos and Eurasian Teal Anas crecca. In Fennoscandia these species have similar breeding habitat requirements but differ in migration distance; Teal migrate roughly seven times as far as do Mallard. Annual ice break-up date was used as a proxy of spring ‘earliness’ to test the potential effect of climate change on hatching timing and breeding performance. Both species were capable of adapting their nesting phenology, and bred earlier in years when spring was early. However, the interval from ice break-up to hatching tended to be longer in early springs in both species, so that broods hatched relatively later than in late springs. Ice break-up date did not appear to influence annual number of broods per pair or annual mean brood size in either species. Our study therefore does not suggest that breeding performance in Teal and Mallard is negatively affected by advancement of ice break-up at the population level. However, both species showed a within-season decline in brood size with increasing interval between ice break-up and hatching. Our study therefore highlights a disparity between individuals in their capacity to adjust to ice break-up date, late breeders having a lower breeding success than early breeders. We speculate that breeding success of both species may therefore decline should a consistent trend towards earlier springs occur.
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