nocturnal

adj

1. Primarily active during the night.

   “nocturnal birds”

2. Taking place at night, nightly.

   “a suspicious nocturnal outing”

   “Many of these classic methods are still used, with some modern improvements. For example, with the aid of special microphones and automated sound detection software, ornithologists recently reported […] that pine siskins (Spinus pinus) undergo an irregular, nomadic type of nocturnal migration.”

noun

1. A person or creature that is active at night.
2. (historical)A device for telling the time at night, rather like a sundial but read according to the stars.

   “A rather different instrument was the nocturnal: it enabled you to tell the time at night, provided you knew the date, from the position of the stars in the constellation of the Great Bear, which rotate around the Pole Star.”