Changes in the Habitat and Nest Site Distribution for Two Lanius Species in Karst Poljes (Bosnia and Herzegovina)

Abstract

This study presents the first comparative analysis for the selection of nesting sites of two shrike species in habitats that were changed after total emigration of the human population. In this area, two shrike species are present (Red-backed Shrike -Lanius collurio and Lesser Grey Shrike -Lanius minor). The selection of nesting sites of two shrike species (breeding population) between two periods was compared: before and after the Balkan civil conflict in three karst poljes (karst fields), municipality of Bosansko Grahovo. Data was collected in 1974-1991 and in 2001-2022 in three karst poljes at Bosansko Grahovo. In total 998 nests of Red-backed Shrikes and Lesser Grey Shrikes (822 and 176 nests respectively) were analysed. The vast majority (67.0% in first and 40.2% in second period) of nests of Red-backed Shrikes were located on the Crataegus monogyna (total 17 species of plants). The Lesser Grey Shrike had the maximum number of nests (over 40%) placed on the two trees/shrubs (C. monogyna and Prunus domesticus) in the first period, and additionally in Sambucus nigra (17.9% of nests) in the second period. Significant differences were found in the selection of nesting sites between these two species and between two periods. Only five trees of nest locations for both species were registered. The Red-backed Shrike prefers lower shrubs (0.8-2.8 m) and Lesser Grey Shrike 3.5-10 m high shrubs/trees. It was confirmed that the presence of suitable nest sites is one of the most important limiting factors determining the distribution of two species in karst poljes.