Hearing a bird vocalizing long after sunset can be confusing, as most species are silent during the night. Yes, some birds do vocalize at night, but the reasons vary greatly depending on the species and environment. These nocturnal sounds are intentional, serving purposes from attracting a mate to defending a territory under the cover of darkness.
Species That Vocalize After Sunset
Birds vocalizing after dark fall into two groups: naturally nocturnal species and diurnal species that extend their singing hours. True nocturnal species are active at night, and their vocalizations are part of their normal routine. This group includes owls, such as the Great Horned Owl, which produces deep hoots, and the Eastern Screech Owl, known for its distinct whinny or trill used for communication between mates or rivals.
Another group of nocturnal vocalizers are the nightjars, like the Eastern Whip-poor-will and the Chuck-will’s-widow. These species use calls for navigation, hunting, and territorial defense, as the night is their primary active period. Conversely, common daytime birds like the American Robin and the Northern Mockingbird also sing past dusk. These species are extending their day, often in response to specific environmental pressures.
Understanding the Causes of Night Singing
For diurnal birds that sing at night, the drivers are often a combination of social and environmental factors. During the breeding season, male birds sing to attract mates and assert their claim over a territory. Unmated male Northern Mockingbirds are frequently the source of continuous, all-night song marathons. Singing for longer hours maximizes their chances of finding a partner.
Artificial light pollution, particularly in urban areas, is a major environmental factor contributing to nocturnal singing. Illumination disrupts the circadian rhythm of species like the American Robin, confusing their internal clock. This perceived daylight prompts them to engage in behaviors normally reserved for the daytime, such as singing.
Scientific studies suggest that many urban birds, including robins, sing at night to take advantage of the reduced noise masking from daytime traffic and human activity. By vocalizing when the environment is quieter, their songs can travel farther and be heard more easily by rivals and potential mates. This adaptation allows them to maintain effective communication in a changing urban soundscape.
Is It a Song, a Call, or an Alarm?
To the human ear, bird vocalizations might sound like a simple “whistle,” but ornithologically, they are categorized into two types: songs and calls. A true song is a longer, complex series of notes produced by a male bird, serving the dual purpose of territorial defense and mate attraction. The sustained, melodic “whistling” heard from a Northern Mockingbird or American Robin is an example of this complex song.
Calls are shorter, simpler, and functional, used for immediate communication like maintaining contact or signaling danger. Most nocturnal species, such as owls, communicate primarily through calls, like the repetitive hooting of a Great Horned Owl used for marking territory. If a diurnal bird is startled at night, the short, sharp sounds it makes are likely alarm calls, distinct from complex songs. Songs are an advertisement, while calls are a direct message.