Displacement and attraction effects caused by transmission powerlines on bird species have been documented, but this topic remains underexplored in the scientific literature. Here, we evaluated the impact of transmission powerlines on bird species typical of open farmlands in the Mediterranean region, focusing on five areas designated to protect farmland birds in Southern Portugal. Using an impact-gradient design, we assessed how birds responded to the proximity of transmission powerlines. Breeding bird data were collected in 2021 and 2022. Our analysis revealed that, after controlling for habitat effects, overall Bird Species Richness and Grassland Bird Species Richness were not significantly influenced by the distance to powerlines. However, species-specific negative effects were observed for two farmland species: the little bustard (Tetrax tetrax) and the calandra lark (Melanocorypha calandra), both showing displacement up to 1 km from the powerlines. These findings indicate no evidence of community-level effects on species richness and no evidence of attraction to powerlines from farmland birds, but confirm species-specific displacement effects, with some species negatively impacted by the presence of the transmission powerlines. The little bustard, a species of high conservation concern that is also highly susceptible to collision with overhead powerlines, requires compensation for habitat loss due to the avoidance effect caused by powerlines.