Plastic Debris in Nests of Two Water Bird Species Breeding on Inland Saline Lakes in a Mediterranean Biosphere Reserve

SIMPLE SUMMARY: Plastic pollution has become one of the main emerging ecological problems that has gained growing public and scientific interest in recent years. In this work, we detected the presence of plastics and other synthetic debris in a less studied ecosystem: inland wetlands. There, we confirmed the presence of anthropogenic materials in the nests of two bird species, the gull-billed tern (Gelochelidon nilotica) and the black-winged stilt (Himantopus himantopus), in a biosphere reserve. The detected debris probably originated from human activities (agriculture and domestic waste) and was probably dispersed by wind and water. Although no damage to the studied species was detected, the situation requires monitoring, which must extend to other wetland points and other species. Our paper records the spread of plastic pollution through wetland ecosystems and its interaction with unexpected wildlife. ABSTRACT: Despite more studies being carried out to know the impacts associated with plastic debris and much effort being spent on marine ecosystems, the impacts of plastics on terrestrial and freshwater species remain largely unknown. Here, we explored the presence of anthropogenic materials in nests of two wader species, the gull-billed tern (Gelochelidon nilotica) and the black-winged stilt (Himantopus himantopus), breeding on the inland salt lakes in the “La Mancha Húmeda” Biosphere Reserve, Central Spain. We revealed the presence of anthropogenic debris, mainly macroplastics (>5 mm), in 2.4% and 12.5% of the sampled nests of the gull-billed tern and the black-winged stilt, respectively. The fragments found in nests ranged from 8 mm to 257 mm for the gull-billed tern and from 7 mm to 19 mm for the black-winged stilt. This debris showed no clear pattern of color or size and probably originated both in the agricultural activities in the surroundings and domestic refuse. Although we did not detect any pernicious impacts on adults or chicks (e.g., entangled, injured, or dead individuals), the presence of plastics and other human waste directly placed in nests located in a protected area should warn us about the ubiquity of these pollutants, and the endocrine and immunological effects, among others, that may reduce the recruitment of new animals to the population should be assessed.