Introduction
During the COVID-19 pandemic, the term “anthropause” was coined to describe the global reduction in human activity. This unusual and temporary decline had a significant impact on the environment ( Rutz, 2022 ). The decrease in human mobility provided a unique opportunity to study how fauna responds to such a reduction ( Bíl et al., 2021 ; Coll, Ortega-Cerdà & Marcarell-Roller, 2021 ; Madhok & Gulati, 2022 ; Markard & Rosenbloom, 2020 ).

The lockdowns and curfews implemented during 2020–2021 provided an opportunity to study the effects of human activity on the environment by comparing conditions before, during, and after the pandemic in sites with varying levels of social mobility restrictions ( Rutz et al., 2020 ). This unique opportunity allowed detailed analysis of the various interactions between humans and wildlife, which is crucial for the development of conservation policies ( Bates et al., 2021 ). The diversity of studies on the effects of the anthropause on animals has increased due to the lockdowns worldwide, indicating that this period was crucial for many species affected by human activity ( Manenti et al., 2020 ; Perkins, Shilling & Collinson, 2021 ; Schrimpf et al., 2021 ).

As a result of the anthropause, changes in animal behavior have been reported worldwide. The use of roads, airports, and recreational areas for resting and breeding by various animal taxa was commonly observed ( Manenti et al., 2020 ; Schrimpf et al., 2021 ). The behavior responses varied depending on the species, type of human mobility, and time scale. For instance, birds which typically fed in residential gardens were seen less frequently because homeowners were more frequently using their backyards for recreation during lockdowns ( Madhok & Gulati, 2022 ). Furthermore, changes in road use during lockdowns led to a significant reduction in wildlife mortality, with notable decreases in wildlife-vehicle collisions in countries like Estonia, Spain, Israel, and the Czech Republic, as well as a 50% reduction in hedgehog mortality on roads in areas of Poland ( Bíl et al., 2021 ; Łopucki et al., 2021 ). The occupancy of beaches by wildlife was also affected during lockdowns. Crabs, endangered sea turtles, iguanas, and various species of seabirds had the opportunity to occupy areas that were frequently visited by tourists ( Soto et al., 2021 ). However, the absence of control, surveillance, and management led to increased threats to native wildlife, due to the invasion of non-native species and illegal hunting in some locations ( Manenti et al., 2020 ).

Among the groups of birds that have benefited from the anthropause are seabirds ( Hentati-Sundberg et al., 2021 ; Schrimpf et al., 2021 ). For example, magnificent frigatebirds ( Fregata magnificens ), laughing gulls ( Leucophaeus atricilla ), and cormorants (Phalacrocoracidae) were commonly observed on urban beaches ( Soto et al., 2021 ). However, other species were affected by the absence of human activity in tourist areas. A reduction in reproductive success in common murres ( Uria aalge ) was reported due to disturbance from white-tailed eagles ( Haliaeetus albicilla ) when tourists were not present in the murres’ breeding areas ( Hentati-Sundberg et al., 2021 ). Nonetheless, while studies of the effects of the anthropause have been conducted on some beaches in Latin America ( Soto et al., 2021 ) marine pollution, particularly plastic contamination, remains a pressing concern worldwide. Lima, a coastal city with over 11 million inhabitants ( INEI , 2022 ), is notably affected, presenting high levels of marine pollution ( Ayala, Cabrera & Quispe, 2007 ; Purca & Henostroza, 2017 ; Tapia et al., 2018 ; Gambini et al., 2019 ). One of the most visited beaches in Lima is the Circuito de Playas Costa Verde (CPCV), which not only receives millions of visitors during the summer but is also with high levels of plastic contamination ( Blondet, Plaza-Salazar & Barona, 2023 ), including microplastics ( De-la Torre et al., 2020 ).

Despite such challenges, along a 16 km stretch of the coastline, CPCV offers areas for recreation, education, sports, and vehicle transit ( Majluf, 2014 ; ATUC, 2022 ). A group of 460 neotropic cormorants are common residents along the CPCV ( Lozano-Sanllehi & Zavalaga, 2021 ). This species is susceptible to indirect plastic ingestion from its prey ( Azzarello & Vleet, 1987 ), making it an indicator for measuring the anthropause’s effect on marine plastic pollution. By analyzing regurgitated pellets with indigestible elements ( Barrett et al., 2007 ), crucial information about the incidence of plastic in the diet of neotropic cormorants can be obtained ( Barrett et al., 2007 ). However, there is a noticeable lack of such information in Peru.

On March 16, 2020, Peruvian authorities implemented the first mandatory COVID-19 lockdown, which endured for several months. Given the circumstances and the notable presence of microplastics on beaches ( Chen & Chen, 2020 ; Bayo, Rojo & Olmos, 2019 ; Retama et al., 2016 ), coupled with the substantial foot traffic typically observed in these areas before the pandemic, it is likely that plastic materials were introduced into the sea through the movement of people between the beach and the water. Furthermore, tourists bathing in the sea contribute to microplastic pollution in coastal waters by shedding textile fibers from their clothing ( Akkajit et al., 2021 ). We hypothesized that during the lockdown in Peru, plastic ingestion by neotropic cormorants would significantly decrease compared to before the lockdowns. Consequently, the objective of this study was to compare the occurrence of plastics in the pellets of neotropic cormorants on CPCV before and during the COVID-19 pandemic.