Brief night-time light exposure changes nesting behavior and links to later body weight in great tits

Exposure to 4 hours of dim light resulted in a small advancing effect on activity onset in great tits.

• Morning light exposure advanced activity onset in incubating great tits compared to dark controls.
• Evening light exposure delayed activity offset compared to dark controls, but morning light did not have a similar effect.
• Breeding success and chick condition remained unaffected by the light treatments.
• Females exposed to artificial light at night had lower weights 9-18 days post-treatment, regardless of exposure timing.
• These findings suggest potential physiological costs associated with artificial light exposure, despite a weak behavioral response.

Simplified