Winter habitat selection and conservation of Hazel Grouse ( Bonasa bonasia ) in mountain forests

The Hazel Grouse (Bonasa bonasia) has suffered from habitat loss due to changes in forestry practices in many regions of Europe. The widespread conversion of structurally heterogeneous to uniform, single-layered stands has caused many of its populations to decline. The trend in multi-functional forestry towards more dynamic processes and natural rejuvenation offers a unique opportunity to restore many habitats of Hazel Grouse in core areas of its actual distribution. As the Alps represent a stronghold of Hazel Grouse distribution in Central Europe, we aimed to determine the species-habitat relationship in mountain forests. We assessed the distribution and characteristics of Hazel Grouse habitat in a forest reserve of the Swiss Alps. Abiotic, structural and vegetation characteristics were investigated at the small scale, and abiotic and forest inventory data at the large scale. We compared the habitat characteristics of used and unused forest stands with a raster system consisting of bird presence and absence cells by applying a logistic regression. Hazel Grouse preferred stands with high proportions of tall rowans, forest edges, and a dense shrub layer at the small scale. Rowans had the strongest influence on Hazel Grouse occurrence. At the large scale, Hazel Grouse preferred forests with large proportions of alder and a diverse mosaic of canopy closure and stand structure. For 44% of the study area, the large-scale model predicted a probability of Hazel Grouse occurrence of more than 0.5. Our data supports the recommendation that the availability of suitable habitat for Hazel Grouse can be increased by natural reforestation of tree-fall gaps and stands with bark beetle infestation, as well as by enhancing the proportion of old-growth stands. Both measures will augment the shrub cover and number of rowan trees, two essential habitat and food resources for Hazel Grouse in mountain forest

The Importance of Spatial Scale in Habitat Models: Capercaillie in the Swiss Alps

The role of scale in ecology is widely recognized as being of vital importance for understanding ecological patterns and processes. The capercaillie (Tetrao urogallus) is a forest grouse species with large spatial requirements and highly specialized habitat preferences. Habitat models at the forest stand scale can only partly explain capercaillie occurrence, and some studies at the landscape scale have emphasized the role of large-scale effects. We hypothesized that both the ability of single variables and multivariate models to explain capercaillie occurrence would vary with the spatial scale of the analysis. To test this hypothesis, we varied the grain size of our analysis from 1 to just over 1100hectares and built univariate and multivariate habitat suitability models for capercaillie in the Swiss Alps. The variance explained by the univariate models was found to vary among the predictors and with spatial scale. Within the multivariate models, the best single-scale model (using all predictor variables at the same scale) worked at a scale equivalent to a small annual home range. The multi-scale model, in which each predictor variable was entered at the scale at which it had performed best in the univariate model, did slightly better than the best single-scale model. Our results confirm that habitat variables should be included at different spatial scales when species-habitat relationships are investigate

Field surveys of capercaillie ( Tetrao urogallus ) in the Swiss Alps underestimated local abundance of the species as revealed by genetic analyses of non-invasive samples

An increasing number of species are becoming threatened by habitat loss and fragmentation. Therefore, solid estimates of the species' abundance in the remaining populations are required to develop suitable conservation measures and to monitor their effectiveness. The capercaillie (Tetrao urogallus L.) has experienced a dramatic decline in central Europe and has disappeared from large areas of its former natural range. In Switzerland, the species' distribution, habitat requirements and demographic status were studied and evaluated in an attempt to support appropriate management decisions to conserve the species. National surveys of the capercaillie in Switzerland have traditionally been obtained from male counts at leks. However, individual attendance to the lek is sex- and age-specific. Thus, male counts at leks may provide a biased estimate of local population sizes. In the present study, we compared two alternative indirect methods to estimate the sizes of local populations at eight study sites situated in the Alps and Prealps of Switzerland. We first assessed the sizes of local populations from the observed density and distribution of direct and indirect evidence of the species' presence during field surveys. Feather and faeces samples collected during field surveys were genotyped at twelve nuclear microsatellite loci and a sex-specific nuclear gene fragment. Individual genotypes were used as genetic tags to estimate the sizes of the eight local populations using an urn model developed for small populations. The index of local population sizes assessed from field surveys was lower than the number of unique genotypes at each study site, which itself underestimated the abundances of populations in most cases. Based on our results, the genetic tagging method appeared to be less biased than the field survey method. However, an alternative faeces sampling scheme, resulting in 2-3genotypings per individual, could further improve the accuracy of the size estimates of local populations. Our study confirms that genetic tagging methods are a valuable tool to estimate the sizes of local populations and to monitor the response of rare and elusive species to management action

Ecological determinants of extrapair fertilizations and egg dumping in Alpine water pipits (Anthus spinoletta)

Behavioral ecology has successfully explained the diversity in social mating systems through differences in environmental conditions, but diversity in genetic mating systems is poorly understood. The difference is important in situations where parents care for extrapair young (EPY) originating from extrapair paternity (EPP), extrapair maternity (EPM), and intraspecific brood parasitism (IBP). In birds, IBP and EPM are rare, but EPP is widespread and highly variable among species and populations. Explanations for this variability are controversial, mainly because detailed ecological information is usually lacking in paternity studies. Here we present results of the first study to identify the ecological determinants of extrapair activities for both sexes of the same species, the water pipit (Anthus spinoletta). DNA fingerprints of 1052 young from 258 nests revealed EPP in 5.2% of the young from 12.4% of the nests. EPM and IBP, both involving egg dumping (EDP), each occurred in 0.5% of the young from 1.9% of the nests. Nests with and without EPY could not be distinguished by traits of the breeders and by reproductive succcess, but they differed with respect to ecology: nests with EPP young were characterized by asynchronous clutch initiation, nests with EPM and IBP young were characterized by higher overlap with neighboring territories and closer proximity to communal feeding sites. We suggest that chance events, resulting from the temporal and spatial distribution of broods, offer a better explanation for the occurence of extrapair activities than female search for genetic or phenotypic benefits. This possibility of "accidental” extrapair reproduction as an "ecological epiphenomenon” with low potential for selection should also be considered for species other than the water pipi

Recent trends in stream macroinvertebrates: warm-adapted and pesticide-tolerant taxa increase in richness

Recently, a plethora of studies reporting insect declines has been published. Even though the common theme is decreasing insect richness, positive trends have also been documented. Here, we analysed nationwide, systematic monitoring data on aquatic insect richness collected at 438 sites in Switzerland from 2010 to 2019. In addition to taxonomic richness, we grouped taxa in accordance with their ecological preferences and functional traits to gain a better understanding of trends and possible underlying mechanisms. We found that in general, richness of aquatic insects remained stable or increased with time. Warm-adapted taxa, common feeding guilds and pesticide-tolerant taxa showed increasing patterns while cold-adapted, rarer feeding guilds and pesticide-sensitive taxa displayed stable trends. Both climate and land-use-related factors were the most important explanatory variables for the patterns of aquatic insect richness. Although our data cover the last decade only, our results suggest that recent developments in insect richness are context-dependent and affect functional groups differently. However, longer investigations and a good understanding of the baseline are important to reveal if the increase in temperature- and pesticide-tolerant species will lead to a decrease in specialized species and a homogenization of biotic communities in the long term

Improved methods for measuring forest landscape structure: LiDAR complements field-based habitat assessment

Conservation and monitoring of forest biodiversity requires reliable information about forest structure and composition at multiple spatial scales. However, detailed data about forest habitat characteristics across large areas are often incomplete due to difficulties associated with field sampling methods. To overcome this limitation we employed a nationally available light detection and ranging (LiDAR) remote sensing dataset to develop variables describing forest landscape structure across a large environmental gradient in Switzerland. Using a model species indicative of structurally rich mountain forests (hazel grouse Bonasa bonasia), we tested the potential of such variables to predict species occurrence and evaluated the additional benefit of LiDAR data when used in combination with traditional, sample plot-based field variables. We calibrated boosted regression trees(BRT) models for both variable sets separately and in combination, and compared the models' accuracies. While both field-based and LiDAR models performed well, combining the two data sources improved the accuracy of the species' habitat model. The variables retained from the two datasets held different types of information: field variables mostly quantified food resources and cover in the field and shrub layer, LiDAR variables characterized heterogeneity of vegetation structure which correlated with field variables describing the understory and ground vegetation. When combined with data on forest vegetation composition from field surveys, LiDAR provides valuable complementary information for encompassing species niches more comprehensively. Thus, LiDAR bridges the gap between precise, locally restricted field-data and coarse digital land cover information by reliably identifying habitat structure and quality across large areas

Soil seed bank responses to edge effects in temperate European forests

Aim The amount of forest edges is increasing globally due to forest fragmentation and land-use changes. However, edge effects on the soil seed bank of temperate forests are still poorly understood. Here, we assessed edge effects at contrasting spatial scales across Europe and quantified the extent to which edges can preserve the seeds of forest specialist plants. Location Temperate European deciduous forests along a 2,300-km latitudinal gradient. Time period 2018-2021. Major taxa studied Vascular plants. Methods Through a greenhouse germination experiment, we studied how edge effects alter the density, diversity, composition and functionality of forest soil seed banks in 90 plots along different latitudes, elevations and forest management types. We also assessed which environmental conditions drive the seed bank responses at the forest edge versus interior and looked at the relationship between the seed bank and the herb layer species richness. Results Overall, 10,108 seedlings of 250 species emerged from the soil seed bank. Seed density and species richness of generalists (species not only associated with forests) were higher at edges compared to interiors, with a negative influence of C : N ratio and litter quality. Conversely, forest specialist species richness did not decline from the interior to the edge. Also, edges were compositionally, but not functionally, different from interiors. The correlation between the seed bank and the herb layer species richness was positive and affected by microclimate. Main conclusions Our results underpin how edge effects shape species diversity and composition of soil seed banks in ancient forests, especially increasing the proportion of generalist species and thus potentially favouring a shift in community composition. However, the presence of many forest specialists suggests that soil seed banks still play a key role in understorey species persistence and could support the resilience of our fragmented forests