Hearing a bird sing a complex melody long after the sun has set is a common experience. This phenomenon, known as nocturnal singing, is any sustained vocalization that occurs outside a bird’s typical diurnal activity period. While most species participate in the dawn chorus, certain birds extend their vocalizations deep into the night. Understanding this behavior requires distinguishing between species that are naturally active at night and those that have altered their schedules.
Which Birds Sing After Sunset
Birds heard singing at night are either truly nocturnal species or diurnal species that sing after dark. Truly nocturnal birds, such as the Common Nightingale and various Nightjars, are naturally active at night, using their songs for communication. The Common Nightingale, for instance, is famous for its complex, fluting song, which is primarily sung by unmated males during the breeding season to attract a partner.
More frequently heard in residential areas are diurnal birds that have adopted nocturnal singing, most notably the Northern Mockingbird and the European Robin. When identifying the sound, it is helpful to distinguish between a “song” and a “call.” A true song is complex, variable, and often extended, designed to attract a mate or defend territory. Short, repetitive, or piercing sounds are typically alarm or contact calls used for signaling danger or maintaining flock cohesion.
The Northern Mockingbird is particularly well-known for its elaborate, varied repertoire, which can include the mimicry of dozens of other species, often sung continuously from a high perch well past midnight. The European Robin, a highly territorial bird, is another species commonly heard singing throughout the night in urban settings. This behavior in typically diurnal birds points to environmental factors affecting their natural rhythm.
The Influence of Artificial Light and Noise
The most common explanation for diurnal birds singing at night involves environmental interference. Artificial light pollution from sources like streetlights and house windows disrupts a bird’s natural circadian rhythm. Birds rely on light cues to regulate their daily cycles, and persistent light can trick them into perceiving night as an extended twilight or early dawn.
This confusion prompts the birds, particularly males driven by hormonal surges, to initiate their dawn chorus prematurely. Birds in artificially lit environments start singing earlier and sing for longer periods than those in naturally dark areas. This misreading of the light cycle shifts a large portion of their vocal activity into the hours traditionally reserved for sleep.
Furthermore, the high level of daytime urban noise pollution creates an acoustic masking effect. During the day, a bird’s song must compete with these loud, low-frequency sounds, which effectively drown out their vocalizations. By shifting their singing to the quieter night hours, birds ensure their songs carry farther and are more easily detected by rivals and potential mates. This strategic timing maximizes the effectiveness of their communication.
Primary Behavioral Reasons for Nocturnal Song
Internal biological drives also motivate nocturnal singing, beyond the environmental pressures of light and noise. The intense competition during the breeding season, especially among unmated males, is the primary driver. A male bird’s prolonged and complex song is an honest signal of his fitness and quality to prospective females.
Unpaired males, like the Northern Mockingbird, may sing almost incessantly, day and night, to maximize their chance of attracting a mate. By extending their vocal displays into the night, they advertise their presence when mated males are typically resting, increasing their competitive edge. The sheer energy expenditure required for continuous singing demonstrates a level of vigor that females find attractive.
Nocturnal vocalization can also be linked to the migratory process. Certain migratory species experience a state of heightened restlessness, known as Zugunruhe, just before or during their nocturnal journeys. While these are often short contact calls used to maintain cohesion in flight, the general state of arousal can also lead to more sustained vocalizations in individuals resting during a migration stopover. For these birds, vocalizing at night may also offer a slight advantage as they can avoid the heightened predation risk from visual hunters that are active during the day.