Pollution caused by anthropogenic debris is a concern for marine biodiversity conservation due to its impact on biota. Debris in seabird nests has been largely unreported in regions like southern South America. Here, novel information is presented regarding the incorporation of marine debris into the nests of Imperial Cormorant (Leucocarbo atriceps) inhabiting the Beagle Channel, Argentina, along an anthropogenic gradient using a photographic method. In doing so, the incorporation of debris was compared under two different scenarios of anthropogenic activities due to the COVID-19 lockdown. The furthest colony away from the city of Ushuaia had no debris at all, while the colony located close to it had a high impact of anthropogenic debris, most of which was plastic. During the lockdown, the colony close to Ushuaia showed a significantly lower proportion of nests (41%) with debris when compared to the following season, with no lockdown (90%). Even more, the amount of anthropogenic debris items per nest increased significantly during the season with no lockdown. Also, the main type of debris varied between seasons, being plastic ropes more dominant during the first season (26%) and plastic bags during the second season (57%). Our study shows that changes in consumer' habits can have a positive impact on seabirds exposed to plastic pollution. Since such changes are possible, we suggest implementing awareness campaigns and seek to establish legal frameworks along with equitable interventions in order to reduce plastic pollution on seabirds' colonies.