Lights Out
Many creatures rely on the darkness of night to avoid predators, to surprise prey, to navigate along their migrations, and to regulate the rhythms of their lives. Light pollution harms wildlife by disrupting these important natural behaviors and cycles. By reducing artificial light at night, we can help birds and other wildlife thrive.
The Problem with Light
Skies over cities can be hundreds of times brighter than a natural, starlit sky. This artificial light at night, which has only appeared very recently in the long evolutionary history of species, is profoundly disrupting ecosystems. Light pollution attracts and disorients migrating and nocturnal species; alters biological processes; changes animal behavior and predator-prey relationships; and contributes to food web disruptions.
Attraction and Disorientation
Many species are fatally drawn to artificial light. Insects are well known to swarm around streetlights and building facades, exhausting themselves or becoming easy prey. Migratory birds, which navigate using stars and other celestial cues, are similarly vulnerable. Skyglow over cities obscures the night sky and attracts birds into urban areas, where illuminated buildings become deadly traps. A study in Chicago found that turning off lights in a single large building reduced bird-window collisions by nearly 60%.
Physiological Effects
Artificial light at night suppresses melatonin, a key hormone impacting sleep, reproduction, and seasonal behaviors. Disrupted circadian rhythms impair immune function, alter metabolism, affect development, and trigger chronic stress responses across species. These physiological impacts can reduce survival and reproductive success even when animals are not directly killed by light.
Behavioral Changes
Light pollution alters how animals interact with each other and their environment. Nocturnal prey species that depend on darkness for protection become more vulnerable in lit areas, while some predators hunt more effectively under artificial light. Birds sing earlier and forage at unusual times. Bats and other light-sensitive species avoid illuminated areas entirely, effectively losing access to otherwise suitable habitat. These behavioral shifts ripple through ecosystems in unpredictable ways.
Food Web and Ecosystem Cascades
The combined impacts of light pollution threaten entire ecosystems. As billions of insects are drawn to their deaths around artificial lights each night, the prey base for birds, bats, fish, and amphibians diminishes. Disrupted pollination by nocturnal insects affects plant reproduction. The loss of light-sensitive species and the behavioral changes in those that remain create cascading effects throughout food webs, ultimately simplifying ecosystems and reducing biodiversity.
Go Lights Out to Save Birds
Reducing artificial light is something we can all do to help protect wildlife.
Personal Actions
Turn off all non-essential lighting from 11 p.m. to 6 a.m. each night during migration seasons (in the Seattle area: April 1-June 1 and September 1-November 1).
- Reduce outdoor lighting.
- Do not use landscape lighting to light up trees or gardens where birds may be resting.
- Shield outdoor lighting fixtures so light is directed only where needed.
- Put lights on timers or motion sensors to reduce the duration lights are on.
- Replace outdoor light bulbs with warm LEDs that are under a 3,000 Kelvin rating.
- You can find “Dark Sky Approved” lighting fixture here.
- Close blinds or curtains at night. This reduces light leakage from inside your home to the outside.
- Make windows safer for birds to help prevent bird-window collisions.
- Report bird-window collisions and other human-related incidinces of bird mortality/injury to DBIRD.ORG.
Take our Lights Out Pledge for more information and resources.
Policy Solutions
Birds Connect Seattle is advocating for Dark Sky and Bird-Safe Buidling regulations. You can help by urging your elected officials to support these important policies.
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