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Six Hong Kong Bird Species Sang Earlier Where Artificial Night Light Was Stronger

Male Oriental Magpie-Robin singing from a branch
Research · Behaviour

Across 20 sites in Hong Kong, six of eight common bird species started their dawn chorus earlier where artificial light at night was stronger. Oriental magpie-robins (Copsychus saularis) were among the earliest singers, beginning on average 119.8 minutes before sunrise. In the standardized model for this species, an increase of one standard deviation in the measured night-light levels corresponded to a 35.5-minute earlier start. In other words, the 35.5-minute estimate describes a standardized step across the light variation in the study, not a fixed increase in lux. The study was published on 24 July 2026 in Ibis.

Researchers recorded birds from 03:00 to 07:00 at 20 sites for 32 days between 10 March and 10 April 2023. They compared the first vocalisation of each species with artificial night light, temperature, rainfall, cloud cover, moonlight and date. Oriental magpie-robins were recorded on 450 dawns across all 20 sites.

Six species started earlier where nights were brighter

Artificial night light was linked to earlier song onset in six species: Asian Koel, Light-vented Bulbul, Common Tailorbird, Oriental Magpie-Robin, Red-whiskered Bulbul and Swinhoe’s White-eye. Blue Whistling Thrush and Masked Laughingthrush showed no clear relationship between dawn-song onset and any of the measured environmental factors. Artificial night light showed the strongest overall association among the factors studied. Higher temperatures were linked to earlier singing in five species. Four species, however, started later when moon illumination was stronger—opposite to what might be expected if any additional light simply advanced the dawn chorus. In oriental magpie-robins, higher temperature and later dates were also linked to earlier singing, while rainfall, moonlight and cloud cover showed no clear relationship.

Recording began too late to capture every earliest song

The authors note that recording began at 03:00, so the true first song may have been missed for some of the earliest singers. Oriental magpie-robins and two other early-singing species sometimes vocalised during the first minute of recording, particularly at brighter sites. Even with that limitation, the broader pattern shows that artificial night light is linked to dawn-song timing in subtropical Hong Kong as well as in the temperate regions where most earlier studies were conducted.

Sources and image credit

  1. To, A. W. Y., & Collins, S. A. (2026). Anthropogenic and natural factors are associated with bird dawn chorus onset in subtropical East Asia.Primary open-access article first published 24 July 2026. Passive acoustic recorders monitored eight common bird species at 20 Hong Kong sites for 32 days. Six species began dawn chorus earlier where artificial night light was stronger, and five began earlier at higher temperatures. Oriental magpie-robins were recorded on 450 dawns, began singing on average 119.83 minutes before sunrise, and showed a 35.5-minute earlier modeled onset per standard-deviation increase in artificial night light.

Image: Jason Thompson / Wikimedia Commons — male Oriental Magpie-Robin (Copsychus saularis) singing at Laem Phak Bia, Phetchaburi, Thailand, photographed 11 January 2013. Representative image of one of the eight study species; not a bird from the Hong Kong study. · CC BY 2.0 — https://creativecommons.org/licenses/by/2.0/ · Source

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