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Institut de recherche pour la conservation des zones humides méditerranéennes

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Titre :	Dispersal of young Black Woodpeckers in connection with the immigration to southern Jutland in Denmark.
Auteurs :	Hans Christensen, Auteur
Type de document :	Article
Dans :	Dansk Ornitologisk Forenings Tidsskrift (96(4) 2002)
Article en page(s) :	161-167
Langues:	Anglais
Résumé :	A small population of Black Woodpecker Dryocopusmartius has been investigated since 1982 in the Danish-German border area (4700 km2, 7% of which is forested, Fig. 1). The number of breeding pairs in the area appears from Fig. 2. A total of 264 nestlings (124 malemale, 140 femalefemale) from 94 broods in 1982-1999 were ringed; a further 23 clutches/broods failed, and one brood was not ringed. By the end of the breeding season in 2000 a total of 65 of the ringed young had been recorded within the study area; 62 (23 malemale, 39 femalefemale) were caught in connection with a project involving colour-ringing of full-grown birds, one male was caught by hand in an urban garden, and two males were recovered dead. Of the 62 chick-ringed and colour-ringed birds, a total of 54 (22 malemale, 32 femalefemale) were later sighted at least once within the study area; 29 (14 malemale 15 femalefemale) were paired when last seen (Table 1) and together accounted for 41% of the 126 known breeding attempts during 1982-2000. The 65 chick-ringed birds recorded within the study area were divided into four categories according to sex and pairing status when last seen. The dispersal distance of the birds (Fig. 4) differed according to category in that unpaired males moved shorter than other birds, whereas no difference was apparent regarding dispersal direction. There was a significant correlation between the dispersal direction of siblings. Movements between the nine southern and four northern woodpecker forests (Fig. 1), thus crossing the sparsely wooded central part of the study area, are shown in Fig. 5. Most birds recorded only as unpaired were seen at one site only, generally during their first Winter (Table 1). Those recorded as paired arrived at their subsequent breeding site at an age of 335 +- 105 days (malemale) or 298 +- 45 (femalefemale). The difference is not statistically significant, but the variance is significantly larger for males than for females. Males first bred in their 2nd (8), 3rd (5) or 5th (1) calendar year, and females in their 2nd (11) or 3rd (4) calendar year. Two birds (siblings from 1984) are known to have emigrated from the study area. Both were sighted in central Jutland about 160 km north of the nest tree where they hatched. Two birds ringed as nestlings in Thuringen and Holstein, respectively, have been found in the area of the present study. Thus, although no preferred direction of dispersal was apparent in the birds staying within the study area, these four long-range dispersers all moved in a northerly direction.

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