<p>Nest architecture is an important component of avian reproductive behaviour, yet variation in the mechanical attachment of nests to supporting vegetation remains poorly documented, particularly in human-modified landscapes. Many birds use flexible natural materials to stabilise open cup nests, but anthropogenic materials may increasingly function as structural “tying” elements where they are locally available. We examined the use of plastic string to attach open cup nests to shrub and tree branches by Red-backed Shrikes (<i>Lanius collurio</i>) across three agricultural landscape types in Poland during the 2021 breeding season (May–August). We monitored 112 nests from egg laying to fledging. Plastic string-mediated attachment to the nesting site was common and strongly tracked local availability of strings near nests. Both litter occurrence and attachment frequency varied markedly among landscape types, being highest in intensive arable fields and lowest in meadows and mixed-crop mosaics. In contrast, nest attachment to the nesting site using plastic strings was not associated with breeding-pair quality, as reflected by the timing of breeding initiation (first egg laying), clutch size, and breeding success. These findings suggest that open cup-nesting birds can plastically exploit readily available anthropogenic strings as a functional structural component to reinforce nest attachment, linking nest-building behaviour to land-use structure and litter distribution in agricultural environments.</p>