The Northern Mockingbird (Mimus polyglottos) is a common bird across North America. While it is a diurnal species, meaning its primary period of activity is during the day, its vocal behavior often leads to confusion. This bird is known for its loud, varied, and persistent singing that frequently extends well into the night, a behavior highly unusual for a diurnal songbird. This nocturnal singing is an exception to its biological norm and is the source of the common misconception that the mockingbird is active after dark.
Establishing Diurnal Behavior
Northern Mockingbirds are programmed for daytime activity, relying heavily on daylight for foraging and survival. Their daily routine is spent actively searching for food, which consists of about half insects and other arthropods in the warmer months, and half berries and fruits during the fall and winter. They employ a unique feeding strategy often described as “flush pursuit,” where the bird runs a few steps on the ground and then flashes its white wing patches, startling insects out of hiding before capturing them.
Nesting and territorial defense are also primarily daylight endeavors. Males typically sing throughout the day, starting about a half hour to an hour before sunrise, to establish and defend their territories. Foraging and caring for young during daylight hours dictates their standard biological clock, making nighttime rest a necessity.
The Source of Nighttime Confusion
The Northern Mockingbird is often mistaken for a nocturnal bird because of the sheer volume, variety, and persistence of its nighttime vocal performance. This bird is an accomplished mimic, a talent reflected in its scientific name, Mimus polyglottos, which translates to “many-tongued mimic.” An individual male can learn and repeat the songs and calls of up to 200 other bird species, and it also incorporates non-avian sounds into its repertoire.
The bird’s song is a complex, continuous string of phrases. Each phrase—often an imitation—is repeated two to eight times before transitioning to the next. When this varied singing occurs in the quiet of the night, it can sound like multiple different birds or an entirely different, unknown nocturnal creature. This complex vocalization, delivered at high volume, draws attention and leads to the assumption that the bird must be primarily active after dark.
Triggers for Singing After Dark
Nighttime singing is an energetically expensive behavior primarily driven by the male’s instinct to reproduce during the breeding season. The vast majority of males heard singing after dark are bachelors actively trying to attract a female. By extending their singing hours, these males increase their chances of advertising their fitness and territory to potential mates. Studies show that the quality and quantity of a male’s repertoire are factors in mate selection, making the nighttime song an intense form of competition.
Another significant influence on nocturnal singing is the increasing presence of artificial light at night (ALAN) in urban and suburban environments. Artificial lights, such as streetlights and porch lights, disrupt the bird’s natural circadian rhythm, effectively extending the day and confusing its internal clock. This light pollution can cause the mockingbird to begin singing up to 20 minutes earlier in the morning and continue up to 30 minutes later in the evening. The quiet environment of the night also allows the song to travel farther without competing with daytime noise, which encourages the behavior.