Plastic waste is the cause of the death of thousands of birds due to ingestion, starvation or entanglement, with marine species being the most affected by this problem [1]. Several articles have shown a growth of bird species that use plastic waste to make their nests [2]. This behaviour has a dangerous repercussion: once the plastic is placed in the nest, it becomes part of the ecosystem, generating pollution in an area where this threat did not exist before [3]. One of these species is the Yellow-legged gull (Larus michahellis atlantis), widely distributed throughout the Macaronesian region, Considering the above, in this work the determination of plastic residues (macro, meso and microplastics) in abandoned yellow-legged gull nests located in two Biosphere Reserves of the Canary Islands (Fuerteventura and Lanzarote) has been carried out. For this purpose, a total of 48 abandoned nests were studied: 15 nests from Lobos island, belonging to Fuerteventura's Biosphere Reserve, and 33 nests from different areas of Lanzarote's Biosphere Reserve (12 from Los Hervideros, 3 from Montaña Clara islet, 8 from the Timanfaya National Park and 10 from Risco de Famara). In total, 803 plastic items were found in the nests: 66 items were separated from the nests taken from Lobos island (4.4 ± 4.6 items/nest), 386 items from those of Los Hervideros (32.2 ± 13.7 items/nest), 25 items from those of Montaña Clara islet (8.3 ± 13.6 items/nest), 324 items from the nests of Timanfaya National Park (40.5 ± 61.6 items/nest) and 2 items from those of Risco de Famara (0.2 ± 0.6 items/nest). The total mass of plastic waste was 17.40 g, 17.07 g corresponding to meso and macroplastics, and 0.26 g to the microplastics fraction. The items most frequently found were nylon lines, fishing nets and wipes.