Is it just me, or are the birds singing more this time of year?
Fernando Igor de Godoy, Folha de Florianópolis, Dec. 2021
Around late August and early September, many people living in some of Brazil’s big cities wake up to the song of thrushes. Those living in rural areas also notice that, during this time, birds seem to be singing more. In the woods, dawn becomes a true symphony of so many songs that it seems impossible to tell who is singing what. But what’s really going on? Do birds actually sing more during this period?
Actually, for many species, yes. This is because it coincides with the breeding season of most birds found in the southern and southeastern regions of Brazil. This period generally starts around the arrival of spring and tends to end in the early months of the following year, between January and February, depending on the species. However, the singing behavior varies quite a bit between species.
Many birds use vocalizations just for communication — either between members of the same species through calls and alarms, or even between different species in interesting mixed-species flocks. But indeed, many species sing more during the breeding season and show increased vocal activity at this time. Birds like thrushes sing more during reproduction, while the rest of the year they tend to be quieter, producing only brief calls. This behavior is common in many species, some of which barely vocalize outside the breeding season. Singing can serve as a display to attract females, with some males producing more elaborate songs, incorporating notes and even imitations of other bird species.
Singing can also be a way for males to mark and defend their territory against rivals. Therefore, some species react aggressively or respond to songs — whether sung by an intruder or imitated by humans through whistles or playback devices. Essentially, the territory owner tries to expel the intruder. This behavior is driven by hormonal peaks during the breeding season that trigger various metabolic reactions.
At dawn, there is also a phenomenon known as the “dawn chorus.” It consists of peculiar songs with long repeated phrases, usually only heard at twilight — at dawn and dusk. This differs from the songs produced throughout the day, sometimes sounding like a different species altogether. The exact function of this chorus is still unknown but is noticeably more intense during the breeding season. Thus, in the first light of spring and summer mornings, birds begin a grand symphony that usually diminishes as the day heats up.
But how do birds know when the breeding season starts? Reproduction is triggered by a combination of factors, including metabolic changes (such as hormones), nervous and reproductive system changes, and environmental cues. Environmental factors — like daylight length, climate, and temperature — are key in timing reproduction because they relate to resource availability. In spring and summer, longer daylight means more foraging time and increased availability of food like flowers, fruits, and insects. This abundance allows many species to find ideal conditions to raise their offspring successfully.
Although many birds sing more at the start of the breeding season, singing often decreases over the following months. This happens because in many species males provide parental care, so they reduce their singing to invest energy in feeding chicks, building nests, etc.
The mentioned breeding period applies to most birds in the region, but there are exceptions. Migratory birds that only pass through may breed at different times and places, like those migrating from the northern hemisphere, which breed in their spring/summer (our autumn/winter). Some birds of prey breed earlier so their young grow during spring and summer when food is more plentiful.
And singing is not the only courtship behavior birds use. Many species, especially males, have elaborate breeding strategies such as dances, bright plumage, or nest building to attract females. So, the breeding season can be detected through many behaviors beyond singing. During this time, you may easily spot a bird carrying a twig or leaf for nest building, feeding a constantly begging chick, or find nests in visible places like dead trees or urban structures. How about observing what the birds in your neighborhood are up to?