What is light pollution?

Light pollution is the human-made alteration of outdoor light levels from those occurring naturally. 

Learn more from DarkSky International. 

Effects of Light Pollution on Birds 

Migration

Many migratory birds fly at night, navigating by stars

• Iowa lies along the Mississippi Flyway, a major nocturnal migration route

Bright lights attract & disorient birds, pulling them off course

Confused birds waste energy circling lit areas

Fatal Collisions

Once drawn into cities by lights, birds collide with windows they can't see or mistake for open sky or habitat

• Up to 1 billion birds die from window strikes in the U.S. each year

Collisions peak during spring and fall migration

• April/May and September/October

Even cities like Ames see deadly impacts —especially near campuses, hospitals, and downtown lights

Health

Light at night disrupts bird health:

• Artificial light scrambles melatonin and natural rhythms

• Birds lose sleep, grow stressed, become active at the wrong times

• Long-term stress cuts survival—especially in urban area

Reproduction

Light throws off reproduction:

• Nighttime singing (to attract mates, defend breeding territories) burns energy and increases predation risk

• Birds nest too early—before food is available

• Chicks raised near lights grow slower, survive less often

Habit 

Light degrades habitat:

• Birds abandon otherwise good nesting sites under constant glow

• Ground-nesting species face higher predator attacks near lit areas

  • Can tip the balance against sensitive species like grassland birds already in decline in Iowa (e.g., Eastern Meadowlark, Dickcissel, Bobolink, Upland Sandpiper, Grasshopper Sparrow)