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BackgroundPopulations living in fragmented habitats may suffer from loss of genetic variation and reduced between-patch dispersal, which are processes that can result in genetic differentiation. This occurs frequently in species with reduced mobility, whereas genetic differentiation is less common among mobile species such as migratory birds. The high dispersal capacity in the latter species usually allows for gene flow even in fragmented landscapes. However, strongly philopatric behaviour can reinforce relative isolation and the degree of genetic differentiation. The Southern Dunlin (Calidris alpina schinzii) is a philopatric, long-distance migratory shorebird and shows reduced dispersal between isolated breeding patches. The endangered population of the Southern Dunlin breeding at the Baltic Sea has suffered from habitat deterioration and fragmentation of coastal meadows. We sampled DNA across the entire population and used 12 polymorphic microsatellite loci to examine whether the environmental changes have resulted in genetic structuring and loss of variation.ResultsWe found a pattern of isolation-by-distance across the whole Baltic population and genetic differentiation between local populations, even within the southern Baltic. Observed heterozygosity was lower than expected throughout the range and internal relatedness values were positive indicating inbreeding.ConclusionsOur results provide long-term, empirical evidence for the theoretically expected links between habitat fragmentation, population subdivision, and gene flow. They also demonstrate a rare case of genetic differentiation between populations of a long-distance migratory species. The Baltic Southern Dunlin differs from many related shorebird species that show near panmixia, reflecting its philopatric life history and the reduced connectivity of its breeding patches. The results have important implications as they suggest that reduced connectivity of breeding habitats can threaten even long-distance migrants if they show strong philopatry during breeding. The Baltic Southern Dunlin warrants urgent conservation efforts that increase functional connectivity and gene flow between breeding areas.

Differing environmental conditions can have profound effects on many behaviours in animals, especially where species have large geographic ranges. Seasonal changes or progression through life history stages impose differential constraints, leading to changes in behaviours. Furthermore, species which show flexibility in behaviours, may have a higher capacity to adapt to anthropogenic-induced changes to their environment. The red-throated diver (RTD) is an aquatic bird, that is able to forage in both freshwater and marine environments, though little else is known about its behaviours and its capacity to adapt to different environmental conditions. Here, we use time-depth recorders and saltwater immersion loggers to examine the foraging behaviour of RTDs from three regions across northwest Europe. We found that in the breeding season, birds from two regions (Iceland and Scotland) foraged in the marine environment, while birds from Finland, foraged predominantly in freshwater. Most of the differences in diving characteristics were at least partly explained by differences in foraging habitat. Additionally, while time spent foraging did not change through the breeding season, dives generally became more pelagic and less benthic over the season, suggesting RTDs either switched prey or followed vertical prey movements, rather than increasing foraging effort. There was a preference for foraging in daylight over crepuscular hours, with a stronger effect at two of the three sites. Overall, we provide the first investigation of RTD foraging and diving behaviour from multiple geographic regions and demonstrate variation in foraging strategies in this generalist aquatic predator, most likely due to differences in their local environment.

Climate change is driving species to shift their distributions toward high altitudes and latitudes, while habitat loss and fragmentation may hamper species ability to follow their climatic envelope. These two drivers of change may act in synergy, with particularly disastrous impacts on biodiversity. Protected areas, PAs, may thus represent crucial buffers against the compounded effects of climate change and habitat loss. However, large-scale studies assessing the performance of PAs as such buffers remain scarce and are largely based on species occurrence data. Conversely, abundance data have proven to be more reliable for addressing changes in wildlife populations under climate change. We evaluated changes in bird abundance from the 1970s-80s to the 2000s inside and outside PAs at the trailing range edge of 30 northern bird species and at the leading range edge of 70 southern species. Abundances of retracting northern species were higher and declined less inside PAs at their trailing range edge. The positive effect of PAs on bird abundances was particularly marked in northern species that rely strongly on PAs, that is, their density distribution is largely confined within PAs. These species were nearly absent outside PAs in the 2000s. The abundances of southern species were in general lower inside PAs and increased less from the 70s-80s to 2000s. Nonetheless, species with high reliance on PAs had much higher abundances inside than outside PAs in the 2000s. These results show that PAs are essential in mitigating the retraction of northern species, but also facilitate northward expansions of southern species highly reliant on PAs. Our study provides empirical evidence documenting the role of PAs in facilitating species to adjust to rapidly changing climatic conditions, thereby contributing to the mitigation of impending biodiversity loss. PAs may thus allow time for initiating wider conservation programs on currently unprotected land.

Climate change has ubiquitous impacts on ecosystems and threatens biodiversity globally. One of the most recognized impacts are redistributions of species, a process which can be hindered by habitat degradation. Protected areas (PAs) have been shown to be beneficial for preserving and reallocating species occurrences under climate change. Yet, studies investigating effects of PA networks on species' range shifts under climate change remain scarce. In theory, a well-connected network of PAs should promote population persistence under climate change and habitat degradation. To study this, we evaluated the effects of PA coverage on avian communities in Finland between two study periods of 1980-1999 and 2000-2015. Climate-driven community impacts were investigated by using community temperature index (CTI). We used linear models to study the association of PA coverage and the CTI changes in southern, central and northern Finland. In northern and central Finland, higher PA coverage was associated with lower changes in CTI and 45% PA coverage in northern and 13% in central Finland corresponded with complete mitigation of CTI increase. These results indicate that higher PA coverage strongly increases community resilience to warming climate. However a similar association between PA coverage and changes in CTI was not apparent in southern Finland. The PA coverage in southern Finland was much lower than in the two other sections and thus, may be too sparse to favour community resilience against climate change. The results provide empirical evidence for the international need to rapidly expand PA networks and halt biodiversity loss.

Human actions have led to loss and degradation of wetlands, impairing their suitability as habitat especially for waterbirds. Such negative effects may be mitigated through habitat management. To date scientific evidence regarding the impacts of these actions remains scarce. We studied guild specific abundances of breeding and staging birds in response to habitat management on 15 Finnish wetlands. In this study management actions comprised several means of vegetation removal to thwart overgrowth. Management cost efficiency was assessed by examining the association between site-specific costs and bird abundances. Several bird guilds exhibited positive connections with both habitat management as well as with invested funds. Most importantly, however, red-listed species and species with special conservation concern as outlined by the EU showed positive correlations with management actions, underlining the conservation value of wetland management. The results suggest that grazing was especially efficient in restoring overgrown wetlands. As a whole this study makes it clear that wetland habitat management constitutes a feasible conservation tool. The marked association between invested funds and bird abundance may prove to be a valuable tool for decision makers when balancing costs and impact of conservation measures against one another.