Why Do Birds Sing At Night?
A number of our readers have written to us to let us know that they have been woken up during the night by bird song.
Nocturnal bird song can be quite common in cities and urban areas and there are two trains of thought that explain this behaviour.
Until fairly recently it was thought that light pollution from street lighting and office buildings was the main reason for birds singing late into the night and early morning.
Light is an important cue by which birds, and all organisms, time their daily and seasonal activities, and changes to natural light sources can fundamentally affect the synchronisation of the circadian clock, or body clock. In the same way we may find it harder to go to sleep if we’ve been staring at a screen for hours before bedtime, birds’ natural cycles will be affected by artificial light sources.
Birds use songs to attract mates, defend territories, and to warn of dangers. They are triggered to start singing in the morning by the first light from the sun and at night sunset gives them the cues they need to stop singing. However, if there is continuous light for 24 hours then birds’ internal clocks may get out of sync and they can start singing much earlier or later than normal daylight hours.
Although this explains why you may hear birds singing in areas with high levels of light pollution it does not answer the question of why you sometimes hear birds singing in winter at night even when it is pitch black.
4 birds you might hear singing at night
Another theory that has been put forward suggests that the high levels of noise in towns and cities during the day is drowning out the calls of some birds forcing them to sing at night instead.
Birds are not only singing at night; they are also having to adapt their songs to get heard. City bird songs are becoming faster and louder with longer pauses between phrases, and birds are leaving out lower pitch notes so they can be heard better.
Blackbirds, for example, can change their entire vocalisation so they can be heard over ambient noise. And a study of great tits found that they sing at a significantly higher pitch in urban areas compared to in the countryside.
Birds may also sing at night if they are woken up by loud noises such as thunder or fireworks. True nocturnal bird song may also trigger usually diurnal birds to sing at night.
Despite nightingales being the most famous of all nocturnal singing birds, with Paul McCartney’s blackbird singing in the dead of night not far behind, the most common singer in the UK’s towns and gardens is in fact the robin. Robins sing all year round and many reports of nightingales singing in the middle of the night during winter have in fact turned out to be robins.
Robins are one of the first birds to start singing in the morning and one of the last to finish at night. As insectivorous birds they are well used to foraging in low levels of light, so street lights can easily trigger them to burst into song.
Other birds that sing at night during the winter, particularly in towns and cities are blackbirds, dunnocks and song thrushes. And in the summer listen out for the true nocturnal birds such as nightjars and corncrakes, as well as diurnal species that sing during the night such as sedge and reed warblers.