This prediction is borne out by the new results.

But the authors of the present study predicted a priori that emergent insects – whose adult flying stages are important sources of food for birds, spiders, bats and reptiles – should likewise be powerful biomonitors for the health of terrestrial ecosystems. The immature stages of aquatic insects – especially stoneflies, mayflies and caddisflies – are known to be highly sensitive to pollution, which is why they have often been used as biomonitors for water quality. In the US, 46% of streams are in poor condition, while 57% of lakes suffer from strong human disturbance. Human activities, such as urbanization and agriculture, have adverse effects on aquatic ecosystems. This study, published in Frontiers in Ecology and Evolution, is one of the first to find evidence for a causal link between the decline of insectivorous birds, the decline of emergent aquatic insects, and poor water quality. In turn, the decline in emergent insects appears to be driven by human disturbance and pollution of water bodies, especially in streams. Image: vagabond54/ShutterstockĪ new study shows that a widespread decline in abundance of emergent insects – whose immature stages develop in lakes and streams while the adults live on land – can help to explain the alarming decline in abundance and diversity of aerial insectivorous birds (ie preying on flying insects) across the US. These findings highlight the need for holistic conservation across terrestrial and aquatic ecosystems.

Scarcity of insect prey in disturbed lakes and streams contributes to bird decline, show new resultsīy Anna Sigurdsson and Mischa Dijkstra, science writersĪ new study shows for the first time that the alarming decline in insectivorous birds across the US may be due to a decline of emergent insects in lakes and streams with poor water quality.

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