Vultures in the southeastern United States ingest more plastic in
landscapes with more developed landcover
Abstract
Plastics are found in ecosystems worldwide and can have widespread
impacts on organisms and the environment. Cathartid vultures, including
the black vulture (Coragyps atratus) and the turkey vulture (Cathartes
aura), have adapted to urbanized environments, making frequent use of
human-made structures and anthropogenic resources. Thus, urban vultures
are likely exposed to more plastic materials than rural vultures, which
they intentionally or unintentionally ingest when foraging or loafing.
Our objective was to determine the extent and type of plastic ingested
by black and turkey vultures in an urban environment by (1) measuring
the plastic content of regurgitated pellets collected along an
urban-to-rural gradient, and (2) identifying the plastics within
pellets. We dissected 1,087 pellets collected at eight vulture
congregation sites in the Charlotte Metropolitan Area, USA between
January 2021 and July 2022. Sixty percent of pellets contained plastic
materials, with an average plastic composition by weight of 2.66 ±
8.76%. Repeated measures linear mixed models of the proportion of
pellets that were plastic suggested that black and turkey vultures are
ingesting more plastic materials when congregation sites are surrounded
by more developed landcover and a greater density of commercial food
providers, such as food stores and restaurants, within 20km. Fourier
transform infrared (FTIR) spectroscopy of a subset of pellets indicated
that the most common types of plastic ingested by vultures were silicone
rubber (used in tires and automobile/boat seals) and polyethylene (used
in plastic bags and food packages). Future research should investigate
the relative importance of plastic sources in vulture diets, vulture
behavioral changes associated with plastic ingestion, and the
consequences of plastic pollution on species health and urban ecosystem
functioning.