Effects of pesticides and vineyard management on the breeding success of the Eurasian wryneck ("Jynx torquilla")

The Eurasian wryneck’s population has experienced a decline due to agricultural intensification, particularly the reduction of available nest cavities and the increase in pesticide use. However, recent efforts in Switzerland have shown a positive trend in the wryneck population through measures such as implementing management methods in vineyards that enhance biodiversity. This study aims to investigate the effects of copper, the most widely used pesticide in our study area, and the impact of different vineyard management practices on the wryneck's breeding success. Ant samples, feathers and feces were collected in vineyards along the littoral of the lakes of Neuchâtel and Bienne and copper was quantified. The proportion of eco-networks were calculated around each nest box occupied from 2017 to 2022. To see the impact of the proportion of eco-networks, the position of the nest boxes and the amount of copper in samples on the breeding success, LMMs and GLMMs were applied. Our analysis unexpectedly found higher copper levels in ants collected from eco-network plots compared to ants from conventionally managed plots. In addition, we found a positive correlation between the amount of copper in ants and in feces. The proportion of eco-networks seems to impact positively the breeding success, without being statistically significant. Moreover, the position of the nest boxes does not seem to impact the breeding success. In conclusion, copper might be accumulating in chicks through ant’s bioaccumulation, without impacting the breeding success of the wryneck. Lastly, eco-networks measures seem to be working for helping the wryneck in vineyards, regardless of the position of the nest box.