Definition:

(adjective) Describes a bird that is most active in low light conditions, typically at dusk and dawn. Crepuscular birds are often insectivorous and feed on insects that are more active before and after the sun is at its strongest, though some also feed on rodents and mammals that are themselves crepuscular. These birds typically have excellent eyesight, and in addition to dusk and dawn, may also be active at night when a full moon provides sufficient light to mimic twilight conditions.

An eclipse can also entice crepuscular birds into more activity.

Crepuscular behavior can also be a defense mechanism. Many predators that could hunt crepuscular birds do not see as well in dim light and instead would be most active either in full daylight or full darkness, giving birds the advantage if they can be active during different periods.

Birds that are primarily crepuscular include swifts, nighthawks, woodcocks, nightjars and many owls. In addition to birds, other creatures such as bats, deer, mice, bobcats and moths are also crepuscular.

Photo – Swallow-Tailed Nightjar © Ben Tavener

Pronunciation:

kreh-PUHS-kyou-lerr