Is it my impression or do birds sing more at this time?
Fernando Igor de Godoy, Folha de Florianópolis, Dec. 2021
In mid to late August and early September, many people living in some of Brazil's big cities are woken up by the song of the thrush. Those who live in rural areas also notice that at the same time, birds apparently sing more. In the bush, the dawn becomes a true mixture of so many corners that it seems impossible to know to whom it belongs. But what really happens? Do birds really sing more?
In fact, for many species, yes. This is due to the reproductive period of most birds present in southern and southeastern Brazil. This period begins approximately with the arrival of spring and tends to end at the beginning of the following year, between January and February, depending on the species. However, the issue of singing varies greatly between each one.
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Many birds present the song (vocalization) only for communication, either between members of the same species, through calls and alerts, or even between other species, with curious relationships, such as mixed flocks. However, in fact, many species do use singing for reproductive purposes and present greater vocal activity at that time. Birds such as thrushes sing more during the reproductive period, while during the rest of the year, they are more shy, producing only brief calls or vocalizations. This behavior is common for several species, and some practically do not vocalize outside of reproduction. Singing can be a form of display for the female, and some individuals may have more elaborate elements, incorporating notes and even imitations, such as the song of other birds.
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The song can also be a tool for delimiting the male's territory and a way of defending it from other invading males. In this way, some species tend to present a more aggressive response to the song, whether emitted by an invader or even through human imitation by whistling or by electronic sound devices (playback). To explain a little bit, the owner of the territory will want to expel the invader. This is because during the breeding season, there is a hormonal peak that generates several metabolic reactions.
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At dawn, there is also a phenomenon known as the "dawn song". It is a peculiar song, with long repetitions of excerpts, which is usually sung only at dusk, that is, at dawn and dusk. This differs from the sounds produced by the bird throughout the day, sometimes even appearing to be another species. The real function of this song is not yet known, but it is notably more pronounced in the reproductive period. Thus, in the first rays of light in spring and summer, the birds begin a great symphony, which tends to be reduced as the day heats up.
But how do birds know when the reproductive period begins? Reproduction is stimulated by a number of factors, whether related to metabolism, as already mentioned for hormones, changes in the nervous and reproductive system, and also environmental factors. Environmental factors such as the amount of light, climate, and temperature are some of the main determinants of the reproduction period precisely because they are related to the amount of available resources. Thus, in spring and summer, due to the greater luminosity, there is a longer foraging time (popularly, demand for food) and also a greater supply of food, such as more flowers, fruits, and insects. This greater supply of resources allows several species to find the best conditions to raise their offspring and ensure their survival.
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Although some birds sing more at the beginning of the breeding season, there may be a reduction in vocalization over the course of the months, even within the season. This is because in many species, males provide parental care, taking care of the offspring and investing energy in feeding the young, building nests, and other activities, which may reduce the time and energy spent on singing.
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The breeding season mentioned typically applies to most birds in the region, but there are exceptions. Migratory birds that pass through locally may breed at different times and in different locations, such as migrants from the northern hemisphere that breed in spring/summer there (when it is autumn/winter in the southern hemisphere). Some raptors may breed earlier, as their young tend to grow in spring and summer, requiring more food than newborns in winter.
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It's important to note that birds use various reproductive strategies beyond singing as part of their courtship behavior. For example, many species have elaborate courtship displays, dances, showy plumage, and nest-building behaviors to attract mates. Therefore, the breeding season can be detected through multiple attributes besides singing. During this time, you may observe birds carrying nesting materials, feeding begging chicks, or even finding nests in conspicuous places such as dry trees or urban structures with relative ease. Why not spend some time observing the birds in your neighborhood to learn more about their behaviors during the breeding season?
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