In the last several years, song in female birds has been documented more and more frequently, thanks to community scientists, sound archives, and dedicated researchers. But for groups of species like flycatchers in which males and females look identical, female song can easily go unnoticed.
New research out this month in the Wilson Journal of Ornithology documented female song in Dusky-capped Flycatchers, a flycatcher species in which the male and female look identical. Glenn Seeholzer, a researcher at the American Museum of Natural History and lead author of the study, says “discovering that female Dusky-capped Flycatchers sing, changed my perspective. If someone had asked me what sex sings the most [when it comes to flycatchers], I probably would have said the male, that is until I stumbled across female song in Dusky-capped Flycatchers.”
Seeholzer didn’t set out to study female bird song, rather Seeholzer set out to examine what happens when two different groups of Dusky-capped Flycatchers come back into contact after being separated by the Andes Mountains in South America for hundreds of years.
Driven by what Seeholzer calls the “museum philosophy,” he set out to record and document everything he could. “You never know what questions your observations will help answer in the future,” said Seeholzer.
Part of the museum philosophy held by many curators and museum scientists is to capture vocalizations along with specimens to facilitate answering as many questions as possible. In fact, Seeholzer’s discovery would not have been possible if he had not diligently captured recordings and specimens together, which allows vocalizations to be directly linked to information about the specimen such as sex and other physical characteristics. But by directly linking his recordings and the physical specimen Seeholzer was then able to determine the sex of each bird in his recordings.
With the help of Francisco Gamarra, a researcher at the University of the Andes in Bogota, Colombia, Seeholzer found that male and female Dusky-capped Flycatchers have different sets of vocalizations that are heard only in a duet. Females often initiate the duet with a female-specific song (a hiccup and raspy roll), which then encourages the male to sing. Females, Seeholzer found, are the dominant vocalizer of the pair, suggesting that females may play an important role in territorial defense. A typical female song sounds like a hiccup or a raspy roll and becomes a duet when the male sings his “wheer” on top of the female songs.
“Vocalizations are a really important place to start better understanding species,” says Seeholzer, and he hopes that this work will help us better understand the role of female vocalizations in sexual selection, territorial defense, and the evolution of female sounds.
Research documenting female song, such as Seeholzer’s and others, is changing how we think about sexual selection. Groundbreaking research in 2014 found that female song is present in 64% of songbird species that exist in the world today and females may play a more important role than previously thought in sexual selection.
Specimens, be they digital or physical can contribute knowledge to many different disciplines, says Seeholzer. “The key is to make museum collections as valuable as possible for as many questions as possible.”
One such question that has intrigued Seeholzer as he was sifting through museum specimens to better understand song in dusky-capped flycatchers, is the presence of wing spurs—tiny clawlike projections on the “elbow” of a bird’s wing. Wing spurs are present in the Tyrant Flycatcher genus Myiarchus, which includes Dusky-capped Flycatchers and 21 other species. Seeholzer thinks that the flycatchers use the spurs to defend their territories. But, the real question is why wing spurs evolved seemingly independently six different times in the tyrant flycatcher and close allies. Seeholzer is actively researching this question and museum specimens will be key to describing this pattern.
Seehozler takes the museum philosophy seriously and has archived all of his recordings in the Macaulay Library. “Because holding onto your recordings in your hard drive won’t do anyone any good,” says Seeholzer. “I like the idea that my recordings are being used by researchers and birders alike, it gives me a greater sense of purpose [to bird recording]].”
Read the paper:
Seeholzer, G. F., and F. J. Gamarra. (2021). A principal role for female vocalization in the repertoire of a tyrant flycatcher revealed by recordings linked to voucher specimens. Wilson Journal of Ornithology. https://doi-org.proxy.library.cornell.edu/10.1676/20-20