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

Description

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.

Steps to reproduce

We trapped Brown-headed Cowbirds at Government Canyon State Natural Area in San Antonio, Texas. We performed gastric lavage with 30 mL of filtered DI water on each individual using a 6.3 cm curved veterinary feeding tube and collected the contents in a sterile sample bag. Cowbirds were then euthanized with 5% isofluorane followed by rapid cardiac compression and the gastrointestinal tracts were removed via dissection. Each individual was prepared as a study skin and vouchered at the Biodiversity Research and Teaching Collections, where tissues and morphometric body measurements were taken. Microplastics were isolated from lavage samples via vacuum filtration and identified to shape and count via dissection microscopy. Microplastics were isolated from GI samples via alkaline digestion in a filtered 10% KOH, 5% citrus toluene degreaser solution at 45C for 48 hours, and filtered vis vacuum filtration. All microplastics were identified and classified via dissection microscopy. The data were formatted to assess the representativeness and efficacy of gastric lavage as non-lethal technique for sampling microplastics in the environment.

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