Raptor research in the province of Groningen (2078 km2) was mainly concentrated in 4 regions, i.e. Oldambt (large-scale arable farmland, with 600 ha of woodlots), Westerwolde (traditional farmland along streams, with 1800 ha of woodland), Duurswold (mixed farmland, with 40 ha of woodlots) and Westerkwartier (small-scale farmland, 225 ha of woodland). Number of territories and breeding success of Marsh Harrier (Table 1), Goshawk (Table 2), Sparrowhawk (Table 3), Common Buzzard (Table 4), Kestrel (Table 5) and Hobby (3 territories with resp. 2, 3 and 3 fledglings) are given for each region. Several breeding parameters and secondary sex ratio of Marsh Harrier, Goshawk, Sparrowhawk. Common Buzzard and Kestrel are detailed for 1990(91)-95 in Appendix 1. Presently, the province of Groningen is holding the major part of the Montagu’s Harrier population in The Netherlands (see Koks 1995, for the Dutch situation in 1994 and 1995).