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Barn Swallow Nestling Diets Differed Between Rural and Urban Himalayan Settlements

Four barn swallow nestlings sitting at the rim of a mud nest under a building roof
Research · Ecology

Barn swallow (Hirundo rustica) nestlings in the Uttarakhand Himalaya received a varied insect diet that differed between rural and urban settlements. Beetle remains occurred in almost every faecal sample, while hymenopterans such as bees, wasps and ants were the second most frequently detected group.

Researchers collected 240 faecal samples from nestlings between March and May 2023 at four breeding sites in northern India: two rural villages and two towns. Prey remains were identified to insect order under a microscope. To compare diet with local prey availability, the team also sampled flying insects along 62 transects at one rural and one urban site. These transects were 50–100 m survey routes that researchers walked at a constant pace while continuously sweeping a net through the air.

Nestling diets differed between rural and urban sites

Beetles occurred in 96.7% of the faecal samples and hymenopterans in 75%. Hemipterans, flies, termites and dragonflies were detected less often. The overall prey composition differed significantly between rural and urban settlements, while there was no significant change across the breeding season when all four sites were analysed together.

Available insects did not fully match the diet

Flies were the most frequently encountered insects in the sweep-net samples, but their remains occurred in only 13% of the faecal samples. The insect community detected in the nestling diet differed significantly from the insects sampled in the surroundings. The authors regard this as evidence of some prey selection, particularly for larger insects, although digestion can also bias the comparison: soft-bodied insects such as flies leave fewer recognisable remains in faeces than chitin-rich prey such as beetles.

Bar charts comparing prey remains and nearby arthropods at rural and urban sites
Frequency of prey remains in nestling droppings (A) and arthropod groups sampled nearby (B). Orange: rural sites; blue: urban sites. Environmental sampling covered only Purola and Nainital. Figure 2, Kaur, Chauhan & Kumar (2026), Avian Conservation and Ecology, CC BY 4.0.

Prey availability was measured at only two of the four diet sites, and the work covered a single breeding season. The authors propose comparisons across several seasons, combining diet and insect availability with measurements of breeding success.

Sources and image credit

  1. Kaur, A., Chauhan, H. P., & Kumar, R. S. (2026). Prey composition in the diet of an avian aerial insectivore – the barn swallow (Hirundo rustica) in the Indian Himalaya. Avian Conservation and Ecology, 21(1), 16.

Image: Fiver, der Hellseher / Wikimedia Commons. Four barn swallow nestlings at Šimuni, Croatia, 15 July 2019. Representative nest photograph, not the study birds. Cropped to 16:9. · CC BY-SA 4.0 · Source

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