Non-native predator control increases the nesting success of birds: American mink preying on wader nests

Abstract The ongoing decline of breeding waderpopulations in Europe has been mostly explained by habitat changes and the increasing impact of native predators, but the influence of non-native invasive predators has been neglected. A seven year study of the nestingsuccess of the northern lapwing, common redshankand black-tailed godwitwas carried out in Biebrza National Park in north- eastern Poland, alongside the American minkcontrol programme, which was undertaken with low and high intensities of minkcontrol. Indices of minkdensity, based on the percentage of floating rafts with minktracks and the number of minktrapped per 100 trap-nights, declined with the increasing number of minkremoved in consecutive years. In our model, the minkcontrol and water level covariates explained most of the variation in daily nestsurvival rates. A decline in minkdensity led to increases in daily survival rates of nestsand to the overall nestingsuccess of all three waderspecies. Lower water levels led to a decrease in the overall daily survival rate (DSR) but this covariate affected DSR differently throughout the breeding season. These results demonstrate that predation by an introduced species, alongside low water levels during the nestingperiod, can limit the nestingsuccess of multiple waderspecies, and that American minkshould be considered as a key predator affecting ground- nestingwetland bird populations. Conservation plansfor many waderspecies declining in numbers should include local reductions in minkpopulations in order to increase nestingsuccess. Thus, intensive continuous minkcontrol is recommended for important nestingrefuges, utilising adaptive managementto ensure control efforts remain sufficiently high.