The original question on Quora was: Can I leave the lights out for my budgies for a few hours in the early evening so they can take a nap?

They usually stay up until 2am with us? 

All birds get an extraordinarily large amount of information from sunlight both the visible spectrum that you and I can see and the invisible spectrum UVA/UVB light.

The light is sent to the pineal gland just behind the right eye where it tells the bird how long the day is and sets off melatonin cells that vibrate like micro metronomes enabling birds to tell the precise time of day – although they don’t know the day.

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