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Institut de recherche pour la conservation des zones humides méditerranéennes

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Titre :	Development of the Magpie Pica pica population in central Copenhagen during 150 years
Auteurs :	David Boertmann, Auteur ; Uffe Gjol Sorensen, Auteur
Type de document :	Article
Dans :	Dansk Ornitologisk Forenings Tidsskrift (100(1) 2006)
Article en page(s) :	9-15
Langues:	Anglais
Résumé :	A 7.18 km(2) area of urban Copenhagen wits surveyed for breeding Magpies Pica pica in 1965 and 1995, and part of the same area ill 2004 (Figs I 2, 3). Moreover, historical sources (Floystrup 1920) made it possible to describe the Magpie population of Copenhagen tit the 1860s and during the years 1909-1919. Our survey area Was Outside tire town in 1860. but in 1909-1919 the Urban development wits almost completed. with housing blocks and streets covering the area except for a few parks and cemeteries.Before the urban development the Magpie was a common bird in the area. then consisting of park-like areas and. outside the city ramparts. of extensive farmland and large gardens with old trees. By 1909-1919 the Magpies had almost disappeared. even from the parks and cemeteries. In 1966, 39 apparently occupied nests (AONs) of Magpie were located in the survey area (5.4 per km(2): Fig. 1). In 1995, 287 AONs were found in the same area (40.0 per km(2): Fig. 2). And tit 2004, 133 AONs (55.8 per km(2)) were found in a 2.38 km(2) Subarea (Fig. 3) where. in 1995, 88 AONs had been counted (37.0 per km(2)).We believe that tire decline of tire Magpie population between 1860 and 1909 was it result of urban development. Almost all trees were probably cut down, reducing available nest sites. During the same period, the species seems to have been increasingly persecuted by humans. We do not know when Magpies began to re-occupy the area. Almost all pairs in 1966 nested in parks with tall trees. and the birds were very shy, but many pair have since established themselves in built-up areas with only few, scattered trees, and the birds have become much more tame (flight distance reduced from more than 50 in to only about 5 in). The increase in the Magpie population was apparently caused by a high survival rate (no shooting) combined with an increase of suitable nesting habitat; the tameness of the birds will have increased the latter trend, making even low trees and bushes available for nesting. The disappearance of the formerly preferred nesting tree, the elm Ulmus glabra, due to Dutch elm disease, had no negative effect on the size of the Magpie population, but led to the utilization of a wider range of nesting tree species in 2004 compared with 1995 (Table 1).

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