Hoe koloniseerden Boomklevers Sitta europaea noordelijk Midden-Drenthe?

Until 1973 Nuthatches were rare breeding birds in the province of Drenthe. Before 1973, only 2-3 pairs occasionally bred in patches of the oldest deciduous forest available, in the northern part of Drenthe. From 1900 onwards, large parts ofheaths and moors were afforested, so that by 1975 the first-planted forests had matured enough to be suitable for Nuthatches to start breeding. From then on, the population started to grow. The study area in northern Central-Drenthe contains 3000 ha of woodland, mostly coniferous and planted in the early 1900s. Patches of old deciduous growth occur in small plots throughout the study area. It was in these patches that breeding of Nuthatches was observed first. Subsequently, Nuthatches filled all niches in the old deciduous parts of the study area before colonisation of younger and more conifer-dominated parts of the forest was attempted (Fig. 3). Until now, colonisation of suboptimal habitats did not slow down the growth rate of the population (Fig. 1). It is concluded that Nuthatches followed the same colonisation pattern at several scales, i.e. in the province of Drenthe (2186 km2), in northern Central-Drenthe (200 km2) and in the Asserbos (0.9 km2). For a bird with such distinct natal philopatry, it was surprising to find that Nuthatches did not disperse evenly from focal breeding sites but first hopped to unoccupied prime breeding habitats (regardless of distance) before settling in less optimal habitats.