Study of Microplastics in Migratory Birds Could Reveal a Broader Environmental Threat

Microplastics are everywhere—in the oceans, the soil, lakes, rivers, and even the air. Yet scientists are only beginning to understand how these tiny plastic particles affect people, animals, and ecosystems. Two Loyola researchers set out to explore the environmental impacts of microplastics by investigating how they accumulate in the digestive systems of birds. They found bits of plastic in the intestines of every bird they examined.

School of Environmental Sustainability (SES) faculty member Stephen Mitten, SJ, collaborated on the study with environmental toxicologist Tham Hoang, PhD, a former Loyola professor who is now on the faculty at Auburn University in Alabama. The researchers examined six bird species, including tree swallow hatchlings collected in Wisconsin and adult ovenbirds, dark-eyed juncos, hermit thrushes, Tennessee warblers, and white-throated sparrows collected on Loyola’s Lake Shore Campus. Members of the Student Operation for Avian Relief Program (SOAR) helped collect the adult birds, which were fatalities from collisions with glass buildings. 

Examination of the birds’ digestive tracts revealed that all contained microplastics in various forms, such as fibers, beads, and fragments. It is unclear exactly how the birds ingested these particles. They could have mistakenly eaten bits of plastic, or they might have consumed contaminated food or water. 

The scientists do not know precisely how ingesting microplastics could impact the birds’ health, but they suspect the particles could be physically and chemically harmful. On the physical level, animals with microplastics in their intestines might not eat enough to survive. Chemically, plastics contain a mix of hazardous chemicals, including substances known to disrupt hormonal systems. Studies of marine organisms have found that exposure to microplastics can cause physical damage and hamper reproduction.

Professor Mitten said that studying microplastics in birds could reveal broader environmental issues. 

“Birds, as they say, are the canary in the coal mine. They are good indicators of what is going on in the environment, and the intake of microplastics by birds and humans is quite evident,” he said.

He said we need to learn more about how microplastics enter the body, how they are eliminated, and how they travel through food chains and ecosystems. If microplastics transfer from aquatic to terrestrial ecosystems, for example, through birds eating aquatic insects, the contaminants could be much more difficult to contain.  

Additional research could reveal more about the role of microplastics in the environment and how to address this growing threat.  

Read the full study, published in the scientific journal Science of the Total Environment.