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Institut de recherche pour la conservation des zones humides méditerranéennes

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Titre :	Population trends of the Common Redstart Phoenicurus phoenicurus in the forests of Baden-Wurttemberg
Auteurs :	Wulf Gatter, Auteur
Type de document :	Article
Dans :	Ornithologischer Anzeiger (46(1) JUL 2007)
Article en page(s) :	19-36
Résumé :	The forestry service of Baden-Wurttemberg has been monitoring nest-boxes for over 50 years. The number of boxes rose annually from 40,000 around 1950 to 160,000 by 1980 and to almost 200,000 by the end of the programme in 1996. Between 1976 and 1996, 9735 successful breeding attempts by Common Redstarts Phoenicurus phoenicurus were recorded. Before 1975, only summarized data are available. Sum totals of treecreepers Certhia spp., flycatchers Ficedula spp. and Common Redstart indicate relatively constant populations until the start of the 1970s. Until ca. 1970 the proportion of boxes occupied by birds other than Nuthatches Sitta europaea or tits Parus spp. was about 4-8%, Common Redstarts making up 0.5-1%. Occupancy rates by Common Redstarts after 1975 were small, maximum 1.5% overall in the woods of forestry directorate (FD) Karlsruhe and just under 0.5% in FD Stuttgart. Flycatchers were ca. 4-5 times commoner. In FD Karlsruhe nestbox occupancy by P. phoenicurus decreased continuously; in FD Stuttgart the decline was slight and not statistically significant. Between 1985 and 1996 the population in the forests of Baden-Wurttemberg (coverage was on average 17% of the state) continued to fall from 0.17 to 0.09 successful nestbox breeding attempts per km(2). Decreasing Common Redstart nestbox populations were noted in the majority of sub-regions in the 1980s and 1990s. Numbers only remained constant at a low level in mixed forests at higher altitudes and in the Odenwald (mainly coniferous). If results from outside areas are included then it becomes clear that weather and climate in the breeding season play only a subordinate role. It was shown that cold winters have a positive effect on Common Redstarts because the numbers of resident birds are reduced.Drought in the African dry savannas (Sahel and Sudan Savannas) between 1968 and 1985 led to dramatic reductions in numbers of Common Redstarts all over Europe. In the forests this effect was eclipsed by other factors, the data showing no population decline following the start of the Sahel drought at the end of the 1960s. Apart from competition with tit species, one limiting factor for the population is that small mammals (in particular Edible and Garden Dormouse Myoxus glis and Eliomys quercinus) act as competitors and predators. Both these species benefit from modern forestry methods and an increased mast crop. In meadow orchards, where dormice are rare, Common Redstart has reached earlier densities. The rapid recovery noted in England, in contrast to the Continent, might be explained by the lack of competition with Black Redstart P. ochruros, as well as the absence of large dormice and the great rarity of Pine Marten Martes martes. Changes in forestry practice have led to an increase in competing species and nest predators. Along with ever denser and darker forests, this appears to be the prime factor for the differing trends in woodland and meadow orchards.It is discussed whether the reduction in potential winter habitats through overgrazing and timber exploitation has caused a decline in the European breeding population, as shown by the abandonment of suboptimal breeding habitats.

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