Tomasz Przybyliński, Krzysztof Myśliwiec
Ornis Polonica 2021, 62: 17–29
https://doi.org/10.12657/ornis.2021.1.2
Abstract: In 2017–2020 the monitoring and active protection of a breeding population of the Montagu’s Harrier Circus pygargus were carried out in Kutno district (central Poland). We aimed to estimate the species number and describe its nesting habitats. Furthermore, we aimed to implement an active protection of nests to prevent the damage of broods during agrotechnical works in the fields. A total of 144 cases of confirmed or probable breeding records were noted. Breeding habitats were described for 112 broods, and they included winter triticale (40.2%), weat (26.8%) and rape (27.7%). We found significant differences between years in the frequency of birds nesting in different crops. Low spring temperatures observed in some years delayed grain growth. As a result more birds laid their clutches among faster growing rape. A total of 75 of 133 clutches (56.4%) was successful. Mean production of fledged young per a breeding pair was 1.59, but there were important differences between years (from 0.71 young/pair in 2017 to 2.0 young/pair in 2019). Of 75 nests 47 were classified as endangered by fieldworks, and hence they were surrounded by a net. The net protected nestlings against terrestrial predators and prevented collisions with agricultural equipment. A total of 91.5% of protected nests were successful (produced at least one fledgling) while the corresponding value for the remaining nests was 78.6% (N = 28). The productivity of pairs whose nests were protected was significantly higher (2.87 young/pair) than that of unprotected nests (1.96 young/pair). These differences may have resulted from the absence of failures caused by mammals in protected nests. Therefore, we can conclude that 39.9% of all fledged young left the nests as a result of protective measures. Nest protection doubled the productivity of breeding pairs in three of four breeding seasons. Productivity of 1.5 young/pair, reached in 2018–2020, should allow to maintain the stable population of Montagu’s Harrier in the area.
Keywords: active nest protection, breeding habitats, Circus pygargus, Montagu’s Harrier, productivity
