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Urban Common Mynas Had Higher Fledging Success, but Rural Nestlings Were in Better Condition

Adult common myna bringing food to a nestling at a tree cavity
Research · Reproduction & development

A nest-box study around Mardan in north-western Pakistan found contrasting effects of urban living on common mynas (Acridotheres tristis). Urban nests had higher fledging success, while rural nestlings generally showed stronger growth trajectories and better body condition. The researchers followed 116 breeding attempts in 200 nest boxes during the 2021 breeding season.

Breeding began earlier in the city. Urban pairs started laying in March, while laying at the rural sites began in April and continued later into the season. Rural nests had longer incubation and nestling periods, but clutch size and brood size did not differ clearly between the two habitats.

More urban nestlings reached fledging

Hatching success was similar in the two environments, but fledging success was significantly higher in urban nests: 86.6% of nestlings fledged, compared with 74.1% in rural nests. Predation was much more frequent in the rural sample, affecting both eggs and nestlings, which helps explain the difference in fledging success.

The higher urban fledging success did not mean that urban nests produced a clearly greater average number of fledglings per nest. The study therefore points to a difference in the proportion of young surviving to fledging rather than a simple increase in brood output across all measures.

Rural nestlings were in better condition

Growth data from 130 urban and 115 rural nestlings showed a different pattern. Rural young generally developed greater body length and longer tarsi at comparable ages, and the authors found better overall body condition in the rural group. Urban nestlings initially had longer wings, but their wing growth was slower. Rural nestlings also gained body mass faster, whereas bill growth and, more slightly, tail growth were faster in urban young. Development therefore responded to the urban–rural environment in a trait-specific way rather than shifting uniformly in one direction.

The authors describe these differences as developmental plasticity: common mynas can adjust their growth and breeding patterns to different environments, but the apparent advantages of urban breeding may come with costs to offspring development.

The mechanisms remain unresolved. Temperature and food availability were not measured directly, adults were not individually marked, and nestling growth was measured only in nests that succeeded. Explanations involving urban heat, food quality, pollution, artificial light or other environmental differences therefore remain hypotheses rather than demonstrated causes.

Sources and image credit

  1. Sadam, A., Hu, H., & Liang, W. (2026). Breeding ecology of the common myna Acridotheres tristis: rural nestlings exhibit enhanced growth compared to urban conspecifics. Journal of Avian Biology, 2026(1), e03545.Primary peer-reviewed open-access research article, first published 29 January 2026. The study compared breeding ecology and nestling growth in 100 urban and 100 rural nest boxes around Mardan, Pakistan.

Image: A. H. M Ibnul Arabi / Wikimedia Commons — adult common myna (Acridotheres tristis) bringing food to young at Rajshahi University, Bangladesh, 15 May 2023; representative breeding photograph, not birds from the Mardan nest-box study. · CC BY-SA 4.0 — https://creativecommons.org/licenses/by-sa/4.0/ · Source

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