Kjell Sjöberg

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.

Habitat change is recognized as one of the main drivers of population declines of species worldwide. In extreme cases, habitat loss and fragmentation may result in population extinctions. On the other hand, habitat suitability may decrease more gradually, in which case species responses may manifest by decreased demographic rates and population density. Boreal wetlands are important breeding habitats for waterfowl in Europe and elsewhere [1]. While loss of wetlands per se is a major threat to waterfowl in many parts of the world [2, 3], gradual degradation of different habitat types within wetlands may also have significant negative impacts on populations. To assess the importance of such habitat changes to waterfowl and to predict their impact on population trajectories, we need a deeper understanding of habitat requirements of individual species and how habitat change affects their fitness. Breeding numbers of Eurasian wigeon (Anas penelope) have declined dramatically in Finland s...

Understanding drivers of variation and trends in biodiversity change is a general scientific challenge, but also crucial for conservation and management. Previous research shows that patterns of increase and decrease are not always consistent at different spatial scales, calling for approaches combining the latter. We here explore the idea that functional traits of species may help explaining divergent population trends. Complementing a previous community level study, we here analyse data about breeding waterbirds on 58 wetlands in boreal Fennoscandia, covering gradients in latitude as well as trophic status. We used linear mixed models to address how change in local abundance over 25 years in 25 waterbird species are associated with life history traits, diet, distribution, breeding phenology, and habitat affinity. Mean abundance increased in 10 species from 1990/1991 to 2016, whereas it decreased in 15 species. Local population increases were associated with species that are early ...

Eurasian migratory duck species represent a natural resource shared between European countries. As is evident throughout human harvest history, lack of coordinated management and monitoring at appropriate levels often leads to ‘the tragedy of the commons’, where shared populations suffer overexploitation. Effective management can also be hampered by poor understanding of the factors that limit and regulate migratory populations throughout their flyways, and over time. Following decades of population increase, some European duck populations now show signs of levelling off or even decline, underlining the need for more active and effective management. In Europe, the existing mechanisms for delivering effective management of duck populations are limited, despite the need and enthusiasm for establishing adaptive management (AM) schemes for wildlife populations. Existing international legal agreements already oblige European countries to sustainably manage migratory waterbirds. Although ...

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.

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. © 2013 The Wildlife Society.

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.

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 reproduc...