Groote Zand (Fig. 1) is a nature reserve in Central Drenthe, 231 ha in size and consisting mostly of woodland (55%) and heathland (43%). Territories were mapped in 1994, using the combined mapping method (Table 1, Appendix 1), and this census was compared with earlier censuses in 1983 and 1989 (Appendix 2). 54 breeding bird species were recorded in 1994, of which 34 were mapped (Appendix 1). Five species are on the Dutch Red List, i.e. Nightjar, Green Woodpecker, Stonechat, Wheatear and Yellowhammer. The composition of the breeding bird fauna showed some important changes between 1983 and 1994 (Appendix 2). Species of sandy heath with scattered trees increased (Nightjar, Woodlark, Wheatear), but those of open heath decreased (Curlew, Skylark, Meadow Pipit). Species typical of small-scale farmland decreased also on the Groote Zand: Turtle Dove, Whitethroat, Tree Sparrow, Linnet and Yellowhammer. Birds of mature woodland increased, such as Lesser Spotted Woodpecker, Redstart and Wood Warbler, but birds of scrub and forestry plantations decreased (Turtle Dove, Dunnock, Bullfinch). These changes were mostly due to natural succession in the vegetation and management.