Microplastic uptake by birds: from observation to development of a novel seed coating to prevent bird predation of corn seeds

The occurrence of microplastics in soil is an emerging issue that not only impacts soil ecology but also has the potential to affect terrestrial birds foraging in agricultural fields. Foraging birds may unintentionally take up soil-borne microplastics along with soil adhering to crop residues and seeds of cultivated species. Microplastic uptake by foraging terrestrial bird species, including Pica pica (magpie), Corvus cornix (hooded crow), and Columba palumbus (common wood pigeon), studied using camera traps, showed that the risk of MP uptake by these birds microplastics from compostable plastic bags was elevated by 27 and 78% when the microplastic particles were associated with corn seed grits or corn seeds, respectively. When these film fragments were coated with a slurry containing tannic acid, saponin, and juglone, microplastic uptake was significantly reduced. Similarly, coating corn seeds with this repellent slurry reduced seed predation by birds up to 86%, and completely wrapping corn seeds with a repellent plastic film resulted in no observed seed predation by birds. The same results were obtained when the wrapping film was replaced by a seed coating containing hairy cotton fibers which may have triggered a feather fear or repulsion response in the birds. This study demonstrated that covering corn seeds with natural repellents or hairy filaments provided complete protection from bird predation.