Breeding habitats and long-term population numbers of two sympatric raptors\u2014Red Kite Milvus milvus and Black Kite M. migrans\u2014 in the mosaic-like landscape of western Poland

Grzegorz Maciorowski,Michał Polakowski,Maria Urbańska,Paulina Król,Piotr Zduniak,Marcin Bocheński

doi:10.1007/s10336-020-01811-7

Abstract

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.

Highlights

Human activities involve exploitation of the natural environment
Both study plots differed in their habitat structure and landscape variety, which in turn gave rise to large differences in the population densities of the two kite species
Densities of breeding pairs of Black Kite (4.07–4.28 pairs/100 km2 in plot A in the two periods, respectively) were consistent with the average densities in this part of Europe (1–20 pairs/100 km2; Rutschke 1983; Gedeon and Stubbe 1991, 1992). This species can occur in much higher densities: e.g., along the River Reuss in Switzerland–48 p/100 km2 (Fusch 1980); near Halle (Germany)–80–130 p/100 km2 (Gedeon and Stubbe 1991, 1992) or even 151 p/100 km2; and as many as 1008 p/100 km2 in Spain

Summary

Introduction

Human activities involve exploitation of the natural environment. In consequence, they change habitat structures, mainly by modifying previously natural landscapes (Xu et al 2018). The strong tendency to cultivate tall crops (mainly maize Zea mays and rapeseed Brassica napus) as large-area monocultures, with the concomitant, dramatic shrinkage of meadows, wetlands and various types of ruderal vegetation, has markedly reduced food availability for raptors. This has a direct negative effect on the breeding performance, distribution and density of breeding pairs in the case of birds that hunt for prey in open areas (Mammen et al 2014; Nicolai et al 2017). Intensive forest management, focusing on large-scale timber production and often final cutting before trees reach maturity, leads to the shrinkage, or even the local disappearance, of mature woodlands in the vicinity of feeding areas used by raptors as breeding sites

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