We studied the long-term changes in numbers and habitat structures of two sympatric species—Red Kite Milvus milvus (RK) and Black Kite Milvus migrans (BK)—in two study plots (a mosaic of various habitats and intensive farmland) in western Poland. This research, carried out in two periods (1996–2001 and 2012–2017), did not reveal any significant changes in numbers, or the parameters of breeding success or habitat structure in the territories of either species. The numbers of RK territories in plot A (mosaic of habitats) in the 2 periods were 35 (density: 3.65 pairs/100 km2) and 38 (3.97 p/100 km2), whereas the respective figures for BK were 39 (4.07 p/100 km2) and 41 (4.28 p/100 km2). Breeding success was 77.4/67.5% (RK) and 63.9/74.6% (BK). On study plot B (intensive farmland), the number of RK territories in both periods were ten (1.35 p/100 km2) and eight (1.08 p/100 km2), while the figures for BK were three (0.41 p/100 km2) and five (0.68 p/100 km2), respectively. The breeding success of RK in the two periods was 87.5%/78.6%, respectively; in the case of BK this Figures (100%) is known only for the second period. The absence of any changes in population numbers for both species and the high levels of breeding success were probably due to the nest sites and mature woods being subject to conservation measures implemented by the Polish State Forests Administration, as well as lack of major changes to the habitat structures. © 2020, The Author(s).