Someone is woken up at dawn by the garbage van loading waste, someone else is disturbed in a decidedly more romantic way by the singing of birds: in fact, many species actually sing at dawn. This phenomenon, studied since the end of the 19th century, is known among ornithologists (bird researchers) like “Dawn Chorus” or “Dawn chorus”. Singing at dawn is useful for reactivating the voice after the silence of the night, for example “mark” the territoryFor attract your partner or for call your teammates back alerting them to the presence of food. No one can forget the Shakespearean reference to the lark, in Romeo and Juliet, whose song at sunrise announces the arrival of the morning, yet some motivations and conditions that induce these vocalizations are still unclear to scholars. Human activity, of course, doesn’t help: many birds are forced to anticipate your calls or “turn up the volume” of their vocalizations to adapt to city life and noise.
Marking of the territory and calling of the partner are the reasons for the vocalizations
The males of great tits (Parus major) they sing at dawn more intensely if the female of the pair moves away and this attitude of recall of the partner it generally occurs in those species in which male and female spend the night together. A group of researchers from the K. Lisa Yang Center for Bioacoustics at Cornell together with the Dhvani Project in India have studied 69 species of birds in a forest environment in the Indian Western Ghats mountain range, a true hot spot of global biodiversity, positioning microphones and sound recorders in different micro-environments of the forest.
Researchers have found that at least 20 species have a peak in singing activity precisely at dawn and for the purpose of mark the territory both for communicate the presence of food to classmates. It is above all highly territorial birds and omnivorous species that are active: the former in this way reaffirm their position and protect the territory, while the latter, eaters of fruit and seeds, exchange communications with their companions to signal the presence of food or any alarm situations. Some species then, in other contexts, seem to adopt this behavior “reactivate” the singing after the silence of the night.
According to ornithologists, the environmental conditions at dawn, generally characterized by less ventilation, higher humidity and low noise, given the same season and weather conditions, can favor the propagation of sounds compared to other moments of the day and, therefore, it is hypothesized that birds sing at dawn even to maximize the transmission of the acoustic signal, but there are still theories on this hypothesis contrasting.
The role of anthropic factors that create disturbance
Many times singing is disturbed by noisy anthropogenic interference especially in certain places and so the birds are forced to adapt their sounds or to adopt various strategies to cope with other noises. For example, the robin in the city advance the time of singing at dawn to precede the onset of noises, other species increase the amplitude and frequency of their vocalizations in response to an increase in background noiseimplementing what has been said Lombard effect (i.e. the tendency a person has to change and raise the tone of voice in a noisy environment).
Similarly, groups of birds of different species nesting near European airports have been studied and it has been discovered that five out of ten songbird species significantly anticipate their morning song compared to a quieter control site, precisely in an attempt to make the vocalization effective before the increase in air traffic and therefore noise.
Which species sing in the morning and in what sequence
There are numerous species of avifauna (set of bird species in an area) that vocalize at the first light of dawn and, if we listen in the woods, in the countryside, but also in urban parks in Europe, especially in the area Mediterraneanit’s easy to listen to the blackbird (Turdus merula), one of the first to start the choir, the robin (Erithacus rubecula) with a very lively and distinguishable song at dawn, the blackcap (Sylvia atricapilla) and a little later towards the morning also the finch (Fringilla coelebs) and the goldfinch (Carduelis carduelis).
The technique with which the singing behaviors of birds are studied is passive acoustic monitoring: ornithologists use automatic acoustic sensors that are conveniently placed outdoors to record sounds and then listen and identify species, also applying acoustic indices to calculate the complexity of the different sounds recorded. It has been observed that the peak of singing It occurs right at dawn and decreases when the sun rises.
