Brown-headed Cowbird paired lavage and GI microplastics data (April-May 2023)

These data were collected as part of a study on microplastic ingestion in Brown-headed Cowbirds (Molothrus ater) to assess gastric lavage as a non-lethal sampling technique. The research was conducted by the authors at Government Canyon State Natural Area near San Antonio, Texas. A total of 105 cowbirds were trapped as part of a cowbird management program, and each bird was assigned a unique identifier. Gastric lavage, involving the use of a veterinary feeding tube, was performed to extract stomach contents. Additionally, the entire gastrointestinal tract was dissected and preserved. The study focused on microplastics in the size range of 1-5 mm, following established best practices for plastic ingestion studies in birds. Visual examination and classification of microplastics by shape (fiber, film, fragment, foam, bead) were conducted under a dissecting microscope. The recovered microplastics from lavage and gastrointestinal samples were quantified and analyzed. The primary objective of collecting this data was to assess the extent of microplastic ingestion in Brown-headed Cowbirds at this site and investigate the efficacy of gastric lavage as a non-lethal sampling method for microplastics. By examining the microplastic loads in both lavage and gastrointestinal samples, the study aimed to determine the representativeness of lavage samples and evaluate the relationship between the two sample types as they relate to the total microplastic load (lavage + GI samples). The research also sought to identify potential pre-exposure factors influencing microplastic recovery rates, such as sex, age, body condition, and trapping site. The data collection process followed established protocols to ensure accuracy and minimize contamination by using blank samples to assess background contamination rates.