Habitat partitioning and molting site fidelity in Tetrao urogallus cantabricus revealed through stable isotopes analysis

Abstract

Sexual dimorphism is often associated with different feeding strategies between sexes because of distinct nutritional demands or intake rates. Capercaillie (Tetrao urogallus) is the most sexually dimorphic grouse, thus sexual segregation in resource use is likely. This study assessed intrapopulation variation in the diet related to habitat use, focusing on differential feeding behaviors between Capercaillie females and males. We used stable isotopes analyses in feathers of Cantabrian Capercaillie, a population living at the southern edge of the range in purely deciduous forests. We analyzed feathers of females and males, and sorted them according to the dominant tree species in the patch where they were found. Mean isotopic values differed both between sexes and among forest types. The latter explained most of the isotopic variance, suggesting that birds consistently selected certain forest types to molt. Capercaillie females showed wider trophic niche and seemingly more intra-gender diversity in resource use than males. The differences between sexes in the trophic variability support the sexual segregation reported in previous studies which is associated with females using the more micro-habitat diverse treeline areas, while males mainly use the inner areas of the forests. Stable isotope analysis proved very useful to assess intersexual niche partitioning in rare species living in rugged terrains where it is logistically difficult to rely on direct approaches (i.e. direct observation, capture and radio-tracking).

Effects of Sexual Dimorphism and Landscape Composition on the Trophic Behavior of Greater Prairie-Chicken

“…Our study provides the first evidence of sexual niche partitioning in North American prairie-grouse which resembles patterns found in old-world forest grouse [4] . We found that females and males showed distinct trophic variability in autumn that was diluted as spring approached ( Fig.…”

“…In grouse (Tetraonidae), sexual dimorphism in body size ranges from large (100%) in Capercaillie ( Tetrao urogallus ) to small (17%) in prairie grouse [23] , [24] . Previous work has shown different aspects of niche segregation in Capercaillie [4] , [25] . In contrast, Greater Prairie-Chicken ( Tympanuchus cupido ; hereafter prairie-chicken ) males and females are expected to show less niche partitioning than Capercaillie based on the smaller size differences between sexes (e.g.…”

“…Niche partitioning often occurs in species that show marked differences in size between males and females and each sex may have distinct nutritional requirements [4] – [8] , resulting in differences in niche breadth and individual diet specialization [7] , [9] , [10] . However, size dimorphism decreases from large to small-bodied lekking species [11] .…”

The role of forest maturity in extreme hydrological events

“…In contrast, the western catchments have not experienced relevant deforestation processes and present mature forest patches. The presence of brown bear (Ursus arctos) and Cantabrian capercaillie (Tetrao urogallus cantabricus) in these catchments, unlike the eastern extreme (Blanco-Fontao, Obeso, Banuelos, & Quevedo, 2012;Gonzalez et al, 2016), is evidence of a better state of conservation. This history of contrasting landscape use in nearby catchments with a similar climate and the existence of contemporary flow gauges and meteorological stations across them make our study area a unique setting for our land cover gradient design.…”

Divergent responses of flagship, keystone and resource‐limited bio‐indicators to forest structure

“…The growth of a complex understory is facilitated by irregularities in the canopy that permit light to reach the lower belt, which is often shaded by a dense canopy in young or managed beech woods but may be exposed in S (+) CV dbh (+) CV h (À) +, positive association; À, negative association D tree species diversity, S shrub species richness, D v vertical species mingling, CV dbh tree diameter variation, CV h tree height variation, BA d standing dead wood undisturbed, old beech stands . Shrubs in lek areas likely provide shelter or foraging habitat for the Capercaillie, which feeds on bilberry leaves and fruits (Storch 1995;Blanco-Fontao et al 2012). The preference of this grouse for upland forests may be related either to the overall higher availability of less-disturbed forest at higher elevations (Garcı´a et al 2005), or to an increase in bilberry quality, an important food source, with elevation (Obeso and Ferna´ndez-Calvo 2002).…”