Long-Term Trends of Hazel Grouse (Tetrastes bonasia) in the Bohemian Forest (Šumava), Czech Republic, 1972–2019

Siegfried Klaus,Tobias Ludwig

doi:10.3390/birds2010009

Abstract

The population dynamics of Hazel Grouse were studied by presence/absence recording at stationary sites along fixed routes (110 km) in the central part of Šumava (Bohemian Forest, Czech Republic) from 1972 to 2019. The 100 km2 study area covered altitudes between 600 m (Rejštejn) and 1253 m above sea level (Mt. Sokol). Our database contained indices of Hazel Grouse occupancy: positive sites/visited sites for a yearly increasing number of Hazel Grouse occurrence sites (n = 134) for 48 years. We used a loglinear Poisson regression method to analyze the long-term population trend for Hazel Grouse in the study area. In the period from 1972 to 2006 we found a stable Hazel Grouse population (p = 0.83). From 2006–2007 to 2019, the population index dropped (−3.8% per year, p < 0.05). This decline is assumed to be influenced by habitat loss due to succession, resulting in older, more open forest stands, by strongly increasing forestry and windstorm “Kyrill”, followed by clear cutting, bark beetle damage, and the removal of pioneer trees in spruce plantations, which diminished buds and catkins, the dominant winter food of Hazel Grouse. The influence of disturbance by increasing tourist activities and/or predation is also discussed. Our results could help to optimize the conservation efforts for Hazel Grouse in the Bohemian Forest.

Highlights

The Hazel Grouse (Tetrastes bonasia) is a cryptically colored, medium-sized forest bird, adapted to multi-layered and old-growth forests with gaps and spots of dense, young forest succession [1,2,3,4,5,6]
Using loglinear Poisson regression, the method can estimate the trends of animal populations based on typically incomplete count data, as was the case with our 134 Hazel Grouse sites
Šumava National Park is a special case in Central Europe, because it is a rare example of a stable Hazel Grouse population over 35 years of study, as shown by our results and earlier work [16]

Summary

Introduction

The Hazel Grouse (Tetrastes bonasia) is a cryptically colored, medium-sized forest bird, adapted to multi-layered and old-growth forests with gaps and spots of dense, young forest succession [1,2,3,4,5,6]. The IUCN (International Union for Conservation of Nature) Red. List of Threatened Species designated the current situation of Hazel Grouse as “least concern” [7]. In Europe, the species’ status was “lower risk” (near threatened) [8] and the EU Birds Directive (2009/147/EC) listed the Hazel Grouse in its Annex I. Red Data books of some Central and Southern European countries, the species is recorded as “vulnerable” (e.g., in Czechia [9]) or “endangered“ (e.g., in Germany [10]), and hunting is forbidden. The European Breeding Bird Atlas-2 documents the large and almost continuous distribution range of the species [11] across the boreal forests, with the highest occurrence probabilities and abundances in Southern Finland and Russia, where suitable habitats of. In the more fragmented range in Central and Western Europe, a high number of squares where the species was not confirmed indicate substantial range losses

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