Early-succession secondary forests following agropastoral abandonment are key winter habitats for the conservation of a priority bird in the European Alps

Abstract

In contrast to old-growth forests, early-successional stands remain understudied despite potentially harbouring species of conservation interest. With this work, focused on hazel grouse Tetrastes bonasia, a cryptic and indicator species known to select for close-to-natural forests, we evaluated winter densities, home range, microhabitat selection and diet, combining DNA-based mark-recapture and metabarcoding from faecal samples. In total, 216 droppings, collected over 2 years along forest transects in the Italian Alps, were successfully genotyped and 43 individuals were identified. Density estimates were similar to values reported by other studies in the Alps with an average of 4.5 and 2.4 individuals/km2 in the first and second study year, respectively, and mean home ranges estimated at 0.95 km2. According to habitat selection models and eDNA-based diet analysis, hazel grouse selected early-succession secondary-growth forests formed after the abandonment of traditional agropastoral activities. These forests, mostly composed of hazel Corylus avellana, Norway spruce Picea abies and Sorbus spp., provided winter food resources and shelter. The diet analysis also highlighted forest arthropods as a non-negligible source of food. Birds avoided areas subject to intensive browsing by ungulates; small forest roads seasonally closed to traffic had positive influence on hazel grouse (i.e. higher abundance of droppings), while roads open to traffic had no effect. Importantly, despite the high coverage of mature forest habitats of Community Interest (53% of our study area), droppings were more abundant in non-listed early-succession secondary forests with similar plant composition. Our results suggest that forest succession after agropastoral abandonment may be beneficial for some forest birds of conservation interest, while acknowledging its negative effects on the previous grassland biodiversity. Graphical abstract

Are forest management practices to improve carbon balance compatible with maintaining bird diversity under climate change? A case study in Eastern North America

“…However, it is important to recognize that such changes in management practices will have varied effects on different bird species. For instance, while some species that thrive in older, undisturbed forests may see population increases, others that depend on early successional habitats or mixed-age forests might experience reduced habitat suitability [85]. This underscores the complexity of forest ecosystems and the need for a nuanced approach to forest management that considers the diverse requirements of different species.…”

Coping with unpredictable environments: fine-tune foraging microhabitat use in relation to prey availability in an alpine species

“…Although it is generally assumed that a forager distribution occurs at the highest prey densities to maximise their intake rate (Holling 1959 ; Stephens and Krebs 1986; Zwarts and Wanink 1993 ; Wallace et al 2015 ; Roder et al 2020 ), there is evidence showing that the overlap between species occurrences and the distribution of key resources may be imperfect due to different constraints including habitat complexity (i.e., detectability; Martinez et al 2010 ; Müller et al 2012 ; Benoit-Bird et al 2013 ; Liu et al 2019 ), presence of predators (e.g., Brown 1988 ; Heithaus et al 2002 ; Clare et al 2023 ), density-dependent effects (Piersma 2012; DeRoy et al 2020 ), as well as limitation associated with the sampling methodology (e.g., Hunsicker et al 2011 ; Kuhn et al 2015 ). In this regard, when both prey and microhabitat availability have been assessed, they have been often evaluated separately over different spatial or temporal extents (Guillemette et al 1992 ; Johnson and Sherry 2001; Barbaro et al 2008 ; Moreno-Rueda et al 2018 ; Scridel et al 2022 ), leading to a potential mismatch between the observation of predators and environmental data such as prey-predator distribution (Hunsicker et al 2011 ; Kuhn et al 2015 ). Modelling microhabitat use and prey availability measured at the same spatio-temporal scale is still rare in the literature (but see Blendinger et al 2012 ; Müller et al 2012 ; Schwemmer et al 2016 ; Aung et al 2022 ), even if this could lead to a more precise inference of whether a species is able to adjust its microhabitat use according to the presence of its prey items.…”

Arrested Succession on Fire-Affected Slopes in the Krummholz Zone and Subalpine Forest of the Northern Limestone Alps

“…The conservation potential of these open subalpine areas is significant both as a refugia for species that are unable to outcompete others while tracking their climatic and biotic niches and as clusters of high diversity [29,34]. Soon after disturbance, these open sites provide habitat to important fauna as well, with the Bavarian Alps homing three endangered species of grouse, namely Tetrao urogallus L., Tetrao tetrix L., and Tetrastes bonasia L., which need a mix of open woodland and grassland to survive [35,36]. In part due to this, the Arnspitze massif in the Northern Limestone Alps has been a designated nature protection area (Naturschutzgebiet) since 1942, ironically five years before the first fire.…”