Bestands- und Brutplatzerfassung von Mehlschwalben (Delichon urbicum, Linnaeus, 1758) und Rauchschwalben (Hirundo rustica, Linnaeus, 1758) im Südwesten und Westen Luxemburgs

Abstract

Population size, distribution and nesting site characteristics of breeding house martins and barn swallows were investigated in the mixed rural and urban landscape of southwestern and western Luxembourg. House martins were mapped in 34 municipalities (670 km2) between 2013 and 2020 and barn swallows in 11 municipalities (228 km2) between 2017 and 2020, representing nearly a quarter and a tenth of the national surface, respectively. By means of one visit per season, nests as well as their occupation status were recorded in a comprehensive mapping effort comprising settlements as well as farmsteads. For the house martin, 4,109 nests were mapped, 1,025 of which were occupied and distributed over 368 colonies with an average number of 2.78 breeding pairs per colony and a population density of 1.62 breeding pairs per km2. Nearly one third of the recorded martin pairs were settled in artificial nests, underlining the effectiveness of this conservation measure. Barn swallow nests numbered 1,395, of which 655 housed breeding pairs, distributed over 107 sites with an average colony size of 6.12 breeding pairs and a population density of 2.89 breeding pairs per km2. Between-year occupancy rates as well as abundances varied strongly between different municipalities in the study area in both species. Generally low breeding densities reflect the unfavourable conservation status for both red-listed swallow species.