Concealment from predators drives foraging habitat selection in brood‐rearing Alpine black grouse Tetrao tetrix hens: habitat management implications

Abstract

Declines of Alpine black grouse Tetrao tetrix populations have been linked to increasing disturbance by recreation and degradation of breeding habitat due to changes in land-use, especially abandonment of traditional farming practices. Appropriate forest, shrubland and grassland management may mitigate the negative effects of land abandonment. The habitat associations and trophic requirements of brood-rearing Alpine black grouse hens were appraised to inform effective habitat management policies. We measured the abundance, biomass and phenology of arthropods, a key food source for grouse chicks, in eight timberline habitat categories and performed a habitat selection analysis based on radio-tracking data collected from eight brood-rearing hens in the Swiss and Italian Alps. Arthropod biomass differed significantly between habitat categories and peaked in early summer due to a sharp increase of orthopterans (Saltatoria), an essential food source for Alpine black grouse chicks. Open grassland and grassy shrubland yielded the highest arthropod biomass, with Saltatoria dominating the sample. Yet, brood-rearing hens avoided open grassland, opting for a mosaic of grassy shrubland with scattered trees. Chick-rearing hens apparently traded-off food abundance for reduced predation risk, i.e. habitats offering cover for concealment and escape from predators. These specific black grouse breeding habitat requirements inform about habitat management within Alpine timberline ecosystems. Managers should not restore extensive, homogeneous pasturelands. Instead, a complex heterogeneous habitat mosaic, consisting of patches of grassland and shrubland interspersed with scattered coniferous trees should be promoted.

Small-scale habitat use of black grouse (Tetrao tetrix L.) and rock ptarmigan (Lagopus muta helvetica Thienemann) in the Austrian Alps

“…Signorell et al (2010) observed higher amounts of epigeal and epiphytic arthropod biomass in open grassland habitats compared to shrublands with scattered trees. However, they observed black grouse brood-rearing hens trading-off food biomass for habitat cover, with the hens apparently selecting shrublands with scattered coniferous trees to reduce predation risk (Signorell et al 2010).…”

“…According to Johnston and Holberton (2009), high abundance of ants and other arthropods is associated with an open forest structure, allowing for the development of the rich ericaceous understorey, which is also essential for black grouse (Beeston et al 2005;Starling-Westerberg 2001). Signorell et al (2010) observed higher amounts of epigeal and epiphytic arthropod biomass in open grassland habitats compared to shrublands with scattered trees. However, they observed black grouse brood-rearing hens trading-off food biomass for habitat cover, with the hens apparently selecting shrublands with scattered coniferous trees to reduce predation risk (Signorell et al 2010).…”

Vegetation structural and compositional heterogeneity as a key feature in Alpine black grouse microhabitat selection: conservation management implications

“…alpenrose Rhododendron ferrugineum, bilberry Vaccinium myrtillus, northern bilberry Vaccinium uliginosum, dwarf juniper Juniperus communis nana, heather Calluna vulgaris, bearberry Arctostaphylos uva-ursi and crowberry Empetrum nigrum) and grasses (e.g. matgrass Nardus stricta, Calamagrostis villosa) represent a characteristic fieldlayer in all areas (Signorell et al 2010). The study areas are characterised by a subcontinental to continental climate, with warm, dry summers and cold, relatively wet winters (Reisigl and Keller 1999).…”

“…Signorell et al 2010) was described through a simple visual ordinal estimate of structural heterogeneity with three levels (low, middle and high, see Online Resource 1). Predictors of vegetation heterogeneity were estimated for Moreover, average habitat feature height (0-3, ascending), number of stumps and grazing activity (presence-absence) were also considered as structural predictors.…”

Declining reproductive output in capercaillie and black grouse – 16 countries and 80 years

“…This may also affect the capercaillie in Switzerland, which selects for open and grazed forests during winter (Sachot et al, 2003). Lower biodiversity might be a consequence of reduced grazing pressure as well as negative impacts on the trade-offs between cover and food-searching that brood-rearing hens exhibit (Signorell et al, 2010). By contrast, in Britain, over-grazing by both red deer (Cervus elaphus) and domestic sheep (Ovis aries) is associated with lower densities of black grouse, lower insect abundance and reduce black grouse reproduction (Baines, 1996;Calladine et al, 2002).…”