Kamil Kaczmarek
Ornis Polonica 2021, 62: 60–73
https://doi.org/10.12657/ornis.2021.1.5
Abstract: In 2017–2020 a breeding population of the Magpie Pica pica was counted in Poznań (W Poland) at housing estates in Rataje district. Within the area of 324.1 ha the number of breeding pairs ranged from 186 to 258. Based on the data from different breeding seasons, an attempt was made to estimate the detectability of the Magpie depending on the seasonal number of visits. My estimates reveal that a single inspection in March–May allows to detect only about 30% of occupied nests. Due to the low detectability of the Magpie, about 75% of nests were classified as occupied on the basis of only one observation of a bird on a nest or in a tree with a nest. For this reason, it is postulated that Magpies should be counted in urban areas 3–4 times during the breeding season (March–May). Other issues related to counting of Magpies in urban habitats are also discussed.
Keywords: counting methods, detectability, Magpie, Pica pica
