Headphones, saw blades, coat hangers: how human trash in Australian bird nests changed over 195 years

Global plastic production has increased exponentially since the 1940s, resulting in the increased presence of rubbish in the environment. Recent studies have shown that birds incorporate human debris such as cigarette butts, into their nests, which can reduce nest parasite loads. However, we know little about the long-term history of interactions among birds, human debris, and nest parasites. Our study took a unique approach to address this issue by analysing Australian museum collections to determine the pattern of human debris and parasitic nest flies in bird nests over time. We studied 893 bird nests from 224 species between 1832 and 2018. We found that the prevalence of human material increased from approximately 4% in 1832 to almost 30% in 2018. This change was driven by an increase in the incorporation of synthetic rather than biodegradable anthropogenic debris (by 2018 ~ 25% of all nests contained synthetics), with the first synthetic item being found in a nest from 1956 in the city of Melbourne. Nest parasite prevalence also increased over time but contrary to other studies, there was no relationship between human materials incorporated into the nest and parasite presence. Our study is the first to use museum specimens to quantify temporal and spatial impacts of anthropogenic material on birds, the results of which justifies contemporary concerns regarding the ubiquitous nature of human impacts on terrestrial wildlife.

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