Human disturbance may have several negative impacts on bird biology. Although some species may habituate to human presence, other species do not show any signs of habituation, and may even be sensitized or affected by human disturbance. Furthermore, anthropogenic effects on bird behaviour rarely have been explored to address the alteration of frequencies of aggressive and fear-associated behaviours. Such behavioural approaches may provide substantial data for bird conservation and management. Therefore, we assessed whether human disturbance disrupts the normal behaviour of Burrowing Owls Athene cunicularia. Specifically, we assessed whether guarding parents exhibited aggressive and fearful behaviours differentially in areas where human contact was more common. Burrowing Owls showed increased frequencies of threat displays in sites with more people walking by the nests, but not fear behaviours. These results suggest that different domains of behaviour (aggression vs. fear) may respond differently to human disturbance. We highlight the importance of quantifying a wide range of behavioural acts as indicators of bird stress in studies of anthropogenic impact.