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Institut de recherche pour la conservation des zones humides méditerranéennes

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Titre :	Patterns and trends in avian species diversity in Denmark
Auteurs :	Hans Meltofte, Auteur ; Michael B. Grell, Auteur ; Timme Nyegaard, Auteur
Type de document :	Article
Dans :	Dansk Ornitologisk Forenings Tidsskrift (104(4) 2010)
Article en page(s) :	120-130
Langues:	Anglais
Résumé :	Patterns and trends in avian species diversity in Denmark Due to Denmark's location close to the border between the temperate and boreal zones and in-between Europe's Atlantic and continental climates the country harbours high levels of biodiversity considering its small size of only 43000 km(2). The breeding bird species were mapped by members of the Danish Ornithological Society during atlas surveys in 1971-74 (Dybbro 1976) and 1993-96 (Grell 1998) using 5x5 km squares.This study presents a simple analysis of patterns and changes in the distribution of different taxonomic and biological groupings of bird species (e.g. passerines and waterbirds) as well as conservation groupings (e.g. the red list and annex 1 of the EC bird directive). Furthermore, point counts made in most quadrants during the second atlas were analysed using Simpson's Diversity Index.The main findings were that the 'young' landscapes glaciated during the last glaciation (i.e. until about 11500 years ago) held significantly more species than the much elder landscapes of West Jutland. This is most likely the result of the 'recently' glaciated landscapes being much more heterogeneous and having more fertile soils. Rare species were to a high extent found in 'marginal' coastal habitats, partly because inland meadows, commons and heath land, which formerly held many of these species, have been lost, and partly because of coastal dynamic processes creating new habitats.Between the two atlas studies, the number of breeding bird species in Denmark increased from 186 in 1971-74 to 200 in 1993-96. Three species had disappeared, while 17 had immigrated. 41% of the Danish breeding bird species increased their distribution significantly (>20%) between the two studies, while 28% decreased significantly (Grell 1998). Increases are thought mainly to be due to overgrowing and euthrophication of the landscape together with better protection of raptors. while decreases mainly are due to intensification of farming and degradation of meadows, commons and heath lands.

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