Female Galápagos Yellow Warbler Song Reveals a Different Story

Scientists long believed that birdsong was the preserve of males, used to attract mates or protect territory. New research reveals a rather different, and more intriguing, picture.

For decades, studies concentrated largely on male birds, while females were assumed to be silent and passive. That assumption influenced how researchers understood birdsong and communication.

A study by the University of Vienna and Anglia Ruskin University challenges that view. Female birds do sing, and their singing is common in many species.

Female song occurs in more than half of all songbird species and may be an ancient trait inherited over generations.

The discovery reveals that an important aspect of bird behaviour went unnoticed by scientists for years.

A surprising song from Galápagos yellow warblers

Researchers investigated Galápagos yellow warblers on Floreana Island. While working in the field, the team heard a song unlike any in the recordings they knew.

They soon identified a female bird as its source. The discovery was notable because previous studies had not recorded female song in this species.

The research provided the first clear evidence that female Galápagos yellow warblers sing both on their own and alongside partners.

It also prompted an important question: if female birds do not sing for the same reasons as males, why do they sing?

Testing bird behaviour

To investigate the purpose of female song, the team devised experiments in the birds’ natural habitat. Researchers played recordings of male songs, female songs and duets.

They observed the birds’ responses during both the breeding and non-breeding seasons. The team measured aggressive actions, such as approaching the sound, and noted how frequently the birds sang.

The approach allowed them to test two common explanations: females might sing to compete with other females, or to defend territory.

Old ideas about birdsong

The findings did not support either explanation. Females displayed considerable aggression, particularly outside the breeding season, but their singing did not correspond to that behaviour.

“Male song was closely linked to aggression during territorial encounters,” explains first author Alper Yelimlieş from the Department of Behavioral and Cognitive Biology at the University of Vienna.

“In females, however, singing and aggression appeared to be unrelated behaviours.”

The study also showed that females responded aggressively to intruders yet sang least often when they heard other females. That pattern does not support the theory that females sing to compete with one another.

Singing changes with the seasons

Females did not sing throughout the year. During the breeding season, only a small number sang, whereas most did so in the non-breeding season.

One possible explanation is that breeding females devote more time to nest-building and caring for eggs. Singing could draw time and energy away from those duties, while singing close to a nest might also attract predators.

Males, by contrast, sang in both seasons and behaved consistently. The difference indicates that males and females may use song in different ways.

Singing together as a pair

Duets were among the study’s most intriguing findings. Females seldom sang by themselves; most of their songs were duets with a partner, usually initiated by the male.

During the non-breeding season, many female songs formed part of a duet. Males, meanwhile, mostly sang solo.

“Most female songs occurred as duets with their paired mates, suggesting that they may function in communication within the pair rather than as a territorial signal,” said Yelimlieş.

“Studying female song is therefore essential for a complete understanding of how vocal communication evolves in birds.”

The results suggest that singing could help partners remain connected or coordinate their actions.

A different purpose for birdsong

The researchers also found that singing did not help females retain territory. Neither song rate nor aggression affected whether a female kept or lost her territory over time.

That finding challenges a widely held explanation for birdsong. Rather than using song to fight or defend space, females may sing to communicate with a partner.

In some circumstances, song could help mates stay close or prevent confusion in tense situations. It might also strengthen the bond between them.

The mystery of female birdsong

The research exposes a significant gap in earlier science. Female birdsong was overlooked for years, limiting understanding of animal communication.

The study demonstrates that both sexes take an active part in communication. It also reminds researchers to challenge long-held assumptions and investigate neglected behaviours.

Female Galápagos yellow warblers sing frequently, particularly outside the breeding season. Their songs are usually duets rather than solo performances, and singing is not directly linked to aggression or territory defence.

The research raises further questions about animal communication and the evolution of song. It also changes how people understand the sounds of nature.