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| 2. |
- Arzel, Céline, et al.
(författare)
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A flyway perspective on food resource abundance in a long-distance migrant, the Eurasian teal (Anas crecca)
- 2009
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Ingår i: Journal of Ornithology = Journal fur Ornithologie. - : Springer Science and Business Media LLC. - 0021-8375. ; 150:1, s. 61-73
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Tidskriftsartikel (refereegranskat)abstract
- Two frequent assumptions about the evolution of long-distance migration in birds are that they travel long distances annually to reach food-rich areas for breeding, and that they time their migratory journey to be at staging sites when the latter provide the best feeding conditions. These assumptions have rarely been properly tested, and there is no study in which a species’ major food types have been measured by standardized methods throughout a flyway and over a large part of the year. We here present such data for Eurasian teal (Anas crecca), converted to a common energetic currency, and collected at wintering, spring staging and breeding sites. Teal did not time migration to maximize local food abundance; most birds left wintering and spring staging sites before a sharp increase in invertebrate food abundance occurred. On the other hand, hatching of ducklings coincided with a peak in invertebrate food abundance on boreal breeding lakes. Mean overall food abundance (invertebrates and seeds combined) did not differ between wintering sites in southern France and breeding sites in northern Sweden at the time of breeding. Our results are inconsistent with the hypothesis that long-distance migration in dabbling ducks has evolved because adult birds gain an immediate pay-off in increased food abundance by flying north in spring. However, our data confirm a selective advantage for breeding at higher latitudes, because hatching of ducklings may coincide with a peak in invertebrate emergence and because longer days may increase the duration of efficient foraging.
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| 3. |
- Arzel, Céline, et al.
(författare)
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Are ducks able to adapt their migratory habits to environmental change?
- 2010
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In order to predict waterfowl population changes due to variation in climate conditions, and habitat availability it is necessary to precisely understand the mechanisms driving their annual cycle. This is particularly challenging in migratory birds as they encounter a huge variety of habitats along their migratory routes, and different factors might affect their demographic parameters at different stages of their life-cycle. In this perspective spring migration stands out as a crucial period. During spring migration birds need both to complete their migration and to prepare for subsequent reproduction. An understanding of long-term factors influencing the timing of breeding in migratory birds is particularly important in order to predict how they might respond to future environmental changes. Anatidae are particularly interesting to study as they offer a wide variety of migratory strategies. We discuss some of the factors that are likely to affect individual choices and thus play a role in the evolution of migration. Based on long-term data sets, collected over 30 years, in the Archipelago Sea, SW Finland, we also offer a first insight into the changes in their spring arrival and breeding success of ducks in relation to environmental conditions.
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| 4. |
- Arzel, Céline, et al.
(författare)
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Average mass of seeds encountered by foraging dabbling ducks in western Europe
- 2007
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Ingår i: Wildlife Biology. - : Nordic Council for Wildlife Research. - 0909-6396. ; 13:3, s. 328-336
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Tidskriftsartikel (refereegranskat)abstract
- Many dabbling ducks Anas spp. are largely granivorous, consuming a variety of seeds chiefly from aquatic plants. To assess the relative value and carrying capacity of wetlands for dabbling ducks, species-specific information about seed mass is needed, but it is still largely missing or scattered in the literature. By combining weights of seeds collected in the field with a literature review, we provide a reference table for seed mass of 200 western European plant taxa frequently encountered by foraging dabbling ducks. Seeds collected in the field were sampled in microhabitats and at depths at which ducks were observed to forage, and study sites represent wintering, staging as well as breeding areas within a flyway in western Europe. When combined with calorimetric data, the present reference table will aid managers and scientists in assessing the importance of seed food resources at different sites and during different parts of the annual cycle.
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| 6. |
- Arzel, Céline, et al.
(författare)
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Does changing spring phenology affect short and long distance migratory waterfowl similarly?
- 2010
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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.
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| 7. |
- Arzel, Céline, et al.
(författare)
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Does foraging in Teal Anas crecca depend on season and disturbance by predators?
- 2006
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- To ensure wise management of migratory species it is crucial to know their energy requirements throughout their biological cycle, especially during periods like spring migration, that might affect future breeding success. Surprisingly, this period has seldom been studied. To start filling this gap for dabbling ducks and especially Eurasian Teal Anas crecca, we studied their foraging time and foraging methods along their Western European flyway from wintering to breeding grounds. Differences in foraging activity between sexes, species, years, seasons, sites and diel patterns were checked, as well as potential effects of disturbances by potential predators. Ducks of both sexes presented a fairly constant nocturnal foraging along the flyway, whereas diurnal foraging increased at periods of high requirements (spring, breeding, moulting). Ducks might thus not only be income breeders, but also income migrators (relying on the food they encounter along their flyway to fuel their travel). Moreover, Teal foraging depth increased along the flyway when disturbance due to potential predators decreased. This probably reflects their diet switch (from granivorous to carnivorous). The decrease in predator pressure probably makes it possible for teals to use riskiest behaviors (greater depths associated to eyes underwater and less prevention of predators).We thus highlight the need for adequate management of staging wetlands all along the flyway, since ducks have to fulfill high energy requirements there. Water level control may be useful to provide more shallow foraging habitats in which they can use less risky foraging techniques at times when nutrient needs increases and predation risk is relatively high.
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| 8. |
- 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-Blackwell Publishing Ltd. - 0019-1019 .- 1474-919X. ; 156:2, s. 288-298
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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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| 9. |
- Arzel, Céline, et al.
(författare)
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Ecology of spring-migrating Anatidae : a review
- 2006
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Ingår i: Journal of Ornithology = Journal fur Ornithologie. - : Springer Science and Business Media LLC. - 0021-8375. ; 147:2, s. 167-184
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Forskningsöversikt (refereegranskat)abstract
- Spring migration is generally considered as a crucial period of the year for many birds, not the least due to its supposed importance for subsequent breeding success. By reviewing the existing literature for Anatidae (ducks, geese, and swans), we show that little is known about their ecology in spring, although some goose species are exceptions. Another general pattern is that the ecology of Anatidae at staging sites is particularly neglected. Existing studies tend to focus on questions dealing with acquisition of nutrient reserves, whereas almost nothing has been published about stopover habitats, time use, microhabitat use, foraging behaviour, food availability, food limitation, diet selection, and interspecific relationships. Besides summarising present knowledge, we identify taxonomic groups and topics for which gaps of knowledge appear the most evident, thereby also highlighting research needs for the future.
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