Skip to content

Almost All Active Barn Swallow Nests Were in Inhabited and Older Buildings in China

Barn swallow chicks in a mud nest under the roof of a building in Aichi, Japan
Research · Ecology

Barn swallows (Hirundo rustica) placed almost all active nests recorded in a three-region Chinese survey in buildings that people still used. Of 942 nests documented in Hainan, Guizhou and Heilongjiang, China, in 2023–2024, 924, or 98.1%, were in inhabited buildings. A total of 866 nests, or 91.9%, were in buildings more than five years old.

Indoor and outdoor nesting differed sharply among regions

The researchers recorded building occupancy and age, whether nests were indoors or outdoors, and nest height. Outdoor nests accounted for 75.1% of the total, but the pattern differed sharply between regions: 98.9% of nests in tropical Hainan and 92.5% in Guizhou were outdoors, compared with only 2.4% in the colder Heilongjiang site. Outdoor nests were also higher on average, at 3.46 m versus 2.64 m for indoor nests.

A separate census of 4,613 buildings in 69 Hainan villages in 2014 found nests in 34.6% of inhabited buildings but only 0.9% of uninhabited ones. Because that census included visible old nests and used a different sampling design, the authors treated it only as a qualitative baseline rather than comparing it directly with the later active-nest surveys.

Living near people may offer advantages, but the study did not test them

The results are consistent with the human-proximity hypothesis, which proposes that some birds gain protection from predators or brood parasites by breeding near people. Older buildings may also offer rougher surfaces for attaching mud nests and existing nests that can be reused. The prevalence of outdoor nesting in Hainan and Guizhou may reflect modern sealed doors and windows, warmer conditions and local attitudes toward indoor nests.

The study measured where swallows nested, not predation rates or reproductive success, so it did not demonstrate that the chosen sites improved survival or breeding output. Building age was also estimated from residents’ reports, and the authors call for direct measurements of survival and breeding success as well as broader, more comparable geographical sampling.

Sources and image credit

  1. Peng et al. (2026), Ecology and Evolution — Nest-Site Selection in Barn Swallows (Hirundo rustica): Patterns Consistent With the Human Proximity Hypothesis Across Three Regions of ChinaPrimary peer-reviewed open-access study, first published 19 July 2026. Detailed surveys recorded 942 active nests in Hainan, Guizhou and Heilongjiang during 2023–2024; 98.1% were in inhabited buildings, 91.9% in buildings older than five years, and 75.1% outdoors. A separate 2014 census covered 4,613 buildings and 1,288 nests in 69 Hainan villages. The authors state that the patterns are consistent with the human-proximity hypothesis, but they did not directly measure predation, reproductive success or other fitness outcomes. The 2014 and 2023–2024 datasets are methodologically different and were not compared quantitatively; building age was based on residents' reports.

Image: KKPCW / Wikimedia Commons — barn swallow (Hirundo rustica) chicks in a mud nest under the roof of a convenience store in Komaki, Aichi Prefecture, Japan, 20 June 2021. Representative East Asian building-nest image; not a nest from the 2023–2024 Chinese study. · CC BY-SA 4.0 — https://creativecommons.org/licenses/by-sa/4.0/ · 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

Ecology

SPECIES IN THIS STORY

Species in this story

Barn Swallow Hirundo rustica Explore species

Independent research and conservation news archive

Did you find this information useful?

Wildlife Vagabond is independently built and maintained. Voluntary support helps cover source verification, hosting and continued work on research and conservation news.

Support Wildlife Vagabond

The news archive will remain freely available.