La Tour du Valat

Institut de recherche pour la conservation des zones humides méditerranéennes

Titre :	Are the declining trends in forest grouse populations due to changes in the forest age structure? A case study of Capercaillie in Finland
Auteurs :	Saija Sirkia, Auteur ; Andreas Linden, Auteur ; Pekka Helle, Auteur ; Ari Nikula, Auteur ; Jonas Knape, Auteur ; Harto Linden, Auteur
Type de document :	Article
Dans :	Biological Conservation (143(6) JUN 2010)
Article en page(s) :	1540-1548
Langues:	Anglais
Résumé :	In Finland, Capercaillie (Tetrao urogallus) populations have a history of serious decrease starting from the mid-20th century. The decline is temporally in line with the expansion of modern forestry practices that created major changes in the landscape. We used tetraonid route-censuses from 18 forestry board districts and Finnish forest inventories (data on forest stand structure) to analyze the decline in 1965-1988. We used information theoretical model selection to evaluate a set of log-linear second order auto-regressive models, allowing for spatially correlated process errors. The average trend throughout the country corresponded to an annual decline of 4.01% (mean of local trends) +/- 0.24% (SEM), parallel to a half-life of 17 years. The decline was surprisingly uniform throughout the country (SD = 1.01%) and most parsimoniously explained by a geographically constant log-linear trend. At the large scale of observation applied here, population trends could not be explained by the proportional increase of younger forest age classes (

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