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Titre :	Population changes of common birds in Denmark, 1975-2004
Auteurs :	Henning Heldbjerg, Auteur
Type de document :	Article
Dans :	Dansk Ornitologisk Forenings Tidsskrift (99(4) 2005)
Article en page(s) :	182-195
Langues:	Anglais
Résumé :	This paper presents results of the Danish Point Count Census for wintering birds 1975/76-2003/04 and for breeding birds 1976-2004. This is the first publication from the project since TRIM replaced the chain method for computing indices and trends. TRIM is preferred to the chain method due to its statistical advantages. This paper provides the basic data on the status for the common bird species in Denmark and in this way constitutes a reference for other studies.Birds are monitored using the point count census method in a free choice scheme. Volunteers select their own route with 10-20 points. Subsequently, at each counting occasion, they count birds for 5 minutes at each point. There is one annual count in winter (between 20 December and 20 January), and one during the breeding season (between I May and 15 June). The habitat around each point is described by ascribing each of the four quadrants around the point to one of 9 habitat categories. Data may be submitted to the coordinators by use of a web-based database called DOFbasen.After a period where the number of routes decreased, the trend is now increasing (Fig. 1). Although not randomly distributed over Denmark, routes are found in all parts of the country (Table 1). The habitat distribution is similar from year to year and from winter to summer, but there are relatively many routes in forests and wetlands and few in farmland areas (Table 2).Table 3 and 4 shows the indices for breeding birds and wintering birds, respectively. For each species the index is set at 100 in the first year with sufficient data to calculate an index (by convention meaning that the species should be recorded on at least

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