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Human Hair and Fishing Line Caused Seven Deaths in Barn Swallow Nests

Four barn swallow nestlings looking out of a mud nest under a wooden roof
Conservation · Threats

Human hair and discarded fishing line were linked to seven fatal entanglements of breeding adults or nestlings in a survey of 193 active barn swallow (Hirundo rustica) nests in China. Researchers checked 123 nests near Danzhou in Hainan and 70 near Zhalong in Heilongjiang every two to three days during the 2024 breeding seasons.

Anthropogenic material occurred in 74 nests, or 38.3% of the total. Human hair was found in 43 nests (22.3%): 42 in Hainan and one in Heilongjiang. Plastic occurred in 42 nests (21.8%): 35 in Hainan and seven in Heilongjiang. Both human hair and plastic were therefore much more frequent in the Hainan nests. Eleven nests contained both hair and plastic.

Human hair and plastic in barn swallow nests, marked with red arrows
Human hair and plastic in barn swallow nests from the study. Red arrows mark the materials. Figure 1, Peng, Yan, Lin & Liang (2026), Ecology and Evolution, CC BY 4.0.

Hair and fishing line caused all recorded deaths

Four deaths in Hainan involved human hair, while three in Heilongjiang involved fishing line. Together, the seven cases represented 3.6% of the nests surveyed. The study is the first to report entanglement mortality caused by human hair in barn swallows. Investigators also frequently found hair wrapped around the feet of live nestlings or caught in their bills and partly swallowed; they removed it by hand when detected.

Anthropogenic nest material can be directly lethal

The authors describe human hair and plastic as a potential direct threat in the human-dominated places where barn swallows often breed. Human hair consists largely of keratin, a resistant protein that can take years to decompose. The authors therefore argue that these materials may turn apparently suitable nest sites into an ecological trap.

The comparison between the two regions was descriptive rather than a controlled geographical test. Nests were found opportunistically and were clustered within each study area, and the authors lacked data from a wider area to quantify the relationship between human disturbance and nest materials.

Sources and image credit

  1. Peng, C., Yan, K., Lin, S., & Liang, W. (2026). Ecological trap in the nest: Human hair causes the death of breeding barn swallows (Hirundo rustica). Ecology and Evolution, 16(5), e73592. https://doi.org/10.1002/ece3.73592

Image: Kakarinka / Wikimedia Commons. Barn swallow nestlings, photographed 9 June 2012. Representative nest photograph, not one of the nests in the Chinese study. Cropped to 16:9. CC BY-SA 3.0: https://creativecommons.org/licenses/by-sa/3.0/ · CC BY-SA 3.0 · Source

About this content: This story was produced with AI assistance within an editorial workflow developed by Wildlife Vagabond. Editorial responsibility remains with Wildlife Vagabond.How AI is used

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