- In California, a group of researchers mapped the sounds of the hermit warbler (Setophaga occidentalis) and analyzed the impacts caused by forest fire on the birds’ songs.
- The researchers found that the diversity of sounds increased in areas that had been affected by forest fires. Three factors impacted the songs: the fires; the massive effect of bird dispersion, which makes room for individuals from other groups to insert their “dialects”; and the time interval due to migration.
- “The result was that some areas have birds singing in more than one dialect, resulting in a complex diversity of sounds in California,” says the study’s lead author.
In the bird world, singing is the way to win a partner or scare off a rival. Whether in love or in war, these sounds convey important messages for a species’ survival. In California, a group of researchers from the Department of Fish and Wildlife recorded the songs of the species known as the hermit warbler (Setophaga occidentalis) and created the first descriptions and mapping of sounds.
Each individual learns the species’ song by imitation, which can cause distinct groups to have cultural variations, much like the regional accents and expressions that human beings have. The songs were divided into 35 “dialects.” In 2019, scientists returned to 10 areas that had been studied and analyzed the impacts caused by forest fires.
Unlike in the Amazon, where fires are the result of environmental crimes, in California they’re part of the ecosystem’s life cycle, a natural mechanism for renewing the forests. As such, changes in birds’ songs do not necessarily represent anything bad. However, with the interference of climate change and human occupation, large-scale fires, such as those in California in the summer of 2018, the most destructive in history, do generate negative impacts.
With data collected since 2009, the American researchers found that the diversity of sounds increased in areas that had been affected by forest fires. The results showed that three factors impacted the songs: the fires; the massive effect of bird dispersion, which makes room for individuals from other groups to insert their dialects; and the time interval.
“The species is migratory. Fires cause a rupture with the departure of the birds that can no longer live in the locale that was destroyed. After a few years, they’re able to return and there is a different dialect,” says Luiza Figueira, a biologist at the Mantiqueira Bird Observatory (OAMa) in Brazil, who was not involved in the recent study.
The researchers said the hermit warbler seems to be especially sensitive to fire during shorter periods of time. At first, the bird is negatively impacted after the fires, but reacts positively in the long run, as the forest is restructured and there is an increase in the insect population. In the case of the hermit warbler, the mating song follows a simple formula. When it comes to defending territory, the sounds are more complex, as if it were literally a dispute to see who comes out victorious. Usually, a single song is dominant within a given territory.
According to the study’s lead author, Brett Furnas, the research suggests that dialects increase in populations in different types of forests. “In the long run, fire caused some birds to flee, creating a vacuum of sound to be filled by other birds. The result was that some areas have birds singing in more than one dialect, resulting in a complex diversity of sounds in California,” he said. Between 2009 and 2014, scientists recorded 1,588 males across 101 areas of study.
Furnas, B. J., Landers, R. H., & Bowie, R. C. (2020). Wildfires and mass effects of dispersal disrupt the local uniformity of type I songs of hermit warblers in California. The Auk, 137(3). doi:10.1093/auk/ukaa031
This story was originally published in Portuguese on Veja.
Banner image of a hermit warbler, by Frode Jacobsen/CC-BY.