Artificial Light at Night Consistently Impacts Avian Physiology and Behaviour: A Meta‐Analysis

Apr 1, 2026Ecology letters

Artificial Night Light Consistently Affects Bird Body Functions and Behavior

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Abstract

A meta-analysis of 675 effect sizes from 36 studies across 30 species indicates that (ALAN) disrupts avian physiology and behaviour.

Physiological changes under ALAN include reduced sleep, higher metabolic rates, and accelerated reproductive maturation.
Birds exhibit extended daily activity patterns, with earlier onset and later offset of activity, as well as increased nocturnal foraging effort.
Migratory bird species show stronger responses to ALAN than resident species, with adults and females more affected than nestlings and males.
The effects of ALAN are amplified with brighter light conditions.
Birds may mitigate ALAN impacts through physiological and behavioural adjustments, suggesting resilience in their life-histories.

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(ALAN) is a major anthropogenic pressure across the tree of life. While ALAN drives population declines in insects and reptiles, birds defy simple patterns. Avian responses to ALAN vary in direction and magnitude, yet the fitness consequences of these responses remain unresolved. We conducted a meta-analysis to test whether ALAN alters avian physiology, behaviour and life-histories, analysing 675 effect sizes from 36 studies across 30 species. We found consistent physiological and behavioural shifts under ALAN, while life-history traits were unaffected. ALAN disrupted physiology through reduced sleep, higher metabolic rate and accelerated reproductive maturation. Behaviourally, daily activity was extended, with earlier onset, later offset, and increased nocturnal activity and foraging effort. Subset analyses revealed stronger ALAN effects in migratory species compared to residents and more pronounced in adults and females than in nestlings and males. Activity shifts, accelerated ageing and sleep disruption were amplified with brighter light. Birds appeared to buffer ALAN effects through physiological and behavioural adjustments, minimising impacts on life-histories, a paradox likely explained by phenotypic plasticity or evolutionary adaptation. We identified key ecological vulnerabilities, emphasising the need for targeted conservation strategies in our increasingly illuminated world.

Key numbers

−1.496

Increased daily activity onset

Mean estimate from meta-analysis indicating shift in timing.

0.474

Higher metabolic rate

Mean estimate indicating physiological response to .

0.649

Accelerated reproductive maturation

Mean estimate reflecting changes in reproductive timing.

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Circadian BiologyIssue #31

Artificial light at night disrupts bird sleep and metabolism across 675 studies

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Artificial Light at Night Consistently Impacts Avian Physiology and Behaviour: A Meta‐Analysis

Abstract

Key numbers

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