Hearing a bird’s voice after sunset is common and prompts questions about which species are active in the dark. Nighttime vocalizations range from complex songs to short, sharp contact calls, distinct from familiar daytime “chirping.” Understanding these sounds requires separating true nocturnal performers from diurnal species whose routines have been altered by external factors.
True Nocturnal Vocalizers
Some bird species are adapted to a life cycle where their primary activities, including foraging and communication, take place under the cover of night. Their calls are a standard part of the nighttime soundscape. The Nightjars, a family of birds, are well-known for their distinct, often loud calls. For example, the Eastern Whip-poor-will is famous for its repetitive, three-syllable chant that can continue for hours during the breeding season.
The Common Nighthawk, another Nightjar species, produces a sharp, nasal call while in flight as it hunts insects. Owls represent a second major group of nighttime callers, though their vocalizations vary significantly by species and purpose. The Great Horned Owl produces a deep, resonant hooting sequence, while the Barred Owl is recognized for its distinctive call often translated as “Who cooks for you? Who cooks for you-all?” These complex calls are primarily used for announcing territory or communicating with a mate.
Specialized species like the Black-crowned Night Heron are also active vocalizers in the dark. These herons feed nocturnally to avoid competition with other wading birds. Their calls are typically short, guttural squawks or barks used to maintain contact or signal their presence. Their vocalizations are an integral part of their natural biological rhythm.
Diurnal Birds Singing After Dark
The sounds of familiar daytime songbirds singing long after sunset often result from environmental factors overriding their natural circadian rhythms. The primary factor influencing this behavior is artificial light at night (ALAN), or light pollution. Streetlights and other human-made illumination can trick diurnal birds into extending their active period by interfering with the dark-light cues that regulate their body clocks.
Studies involving hundreds of diurnal species show that light pollution can prolong their vocal activity by an average of 50 minutes compared to birds in dark areas. Species with larger eyes, such as the Killdeer, appear to be more sensitive to this light interference, causing a greater impact on their daily routines. The Northern Mockingbird is a common example of a bird that frequently sings at night, often influenced by bright urban lighting.
Another contributing factor is the high level of ambient noise, such as traffic, present during the day in urban environments. Some birds delay communication until the evening when background noise levels drop significantly. This creates a clearer acoustic channel for their songs to travel, allowing their messages to be heard more effectively. Singing after dark is a behavioral adjustment to the altered urban landscape rather than a natural preference.
The Function of Nighttime Calls
The sounds birds make after dark serve specific biological purposes. One common function of sustained nighttime singing, particularly during spring and summer, is mate attraction and territorial defense. Unpaired male birds, such as the Northern Mockingbird, may sing extensively through the night to advertise their fitness and claim breeding territory when competition is low. The clarity of the nighttime soundscape allows the song to travel farther, increasing its effectiveness in signaling potential mates.
For many smaller songbirds, short, distinct sounds known as nocturnal flight calls (NFCs) are commonly heard overhead during migration seasons. Most songbirds migrate at night to avoid predators and take advantage of cooler, more stable air conditions. These flight calls are species-specific and distinct from breeding songs, confirming they are not used for mate attraction.
The primary function of these brief, high-pitched calls is to maintain group cohesion and coordinate movements within migrating flocks. These short vocalizations help individuals keep track of one another while traveling in the darkness. This complex communication system manages the large-scale movement of birds across the night sky.