Known for their beautiful, lyrical songs, songbirds are one of the most diverse clades of birds, consisting of over 4,000 species (Encyclopaedia Britannica). Their most fascinating behavior is the ability to produce such distinctive, elaborate songs. Much like humans, songbirds have a highly sophisticated form of communication. In fact, very few other animals learn vocalization through social interactions. During their first few months, songbirds learn and individualize a repertoire of songs essential for mating and territorial defense. Thus, song learning (also called song sharing) is crucial for their own fitness and survival. Yet, the question remains: how is this behavior advantageous for the adult tutors? What do they get out of teaching their songs to young juveniles? Or is this a competitive system where juvenile birds imitate the “tutors”? Though previous studies have explored juvenile song learning, the recent study, by Micheal Beecher and colleagues, examines if song learning is also favorable to adult songbirds. Beecher and colleagues reached a surprising conclusion; song learning in Song Sparrows supports a mutually beneficial relationship between the tutee and tutor. Not only does learning a repertoire of songs from a primary tutor increase survivorship of the juvenile Song Sparrow, it also increases the survivorship of the tutor or adult teacher (Beecher et al. 2020).
“We often first think of bird song as a type of territory defense, or a mate attraction behavior,” says biologist and Professor of Animal Behavior at Kenyon College, Iris Levin. “Therefore, cooperation or some mutual benefit is not the first thing that comes to mind. This study by Beecher and colleagues….shakes the paradigm a bit.” Levin was not involved in this study, but as an ecologist who studies Barn Swallows and has published previous research on songbirds, she is excited by the implications of this study.
It may seem like the study of songbirds is an irrelevant area of research, but studies such as these are important because it may help us understand how to increase the survival of older and younger generations – through the preservation of tutor/tutee relationships – especially with decreasing populations. Furthermore, this may provide insight into human language development. Levin is intrigued by the possibilities for continuing this vein of research. “I’d be really interested to see whether reproductive success is also higher for these males who appear to be benefiting by singing the same songs.”
For songbirds, the process of learning a song is akin to learning how to play an instrument. Learning to play an instrument often requires a teacher of some sort: whether that be youtube, a neighbor, or a private tutor. Oftentimes this teacher is unrelated to you but resides close enough to take lessons. Likewise, songbirds learn from outside tutors rather than their parents. Within their first year of life, they build a repertoire of songs by learning and replicating the notes of their primary tutor while also adding their own style. By the time the Song Sparrow has established his territory, he has cemented his song repertoire of about 6-13 songs.
There is considerable evidence that young male songbirds benefit from learning particular songs to attract a mate and reproduce. However, it has long been assumed that there are no costs or benefits associated with the tutor because these songbirds learn from unrelated members, and therefore song learning is merely a one-way relationship that increases the juvenile’s fitness. Beecher and colleagues tested these assumptions by measuring the survival of a tutee and his primary tutor in relation to how many songs were learned in a population of Song Sparrows, Melospiza melodia morphna (Beecher et al. 2020).
Beecher and colleagues conducted their field study in a park adjacent to the Puget Sound in Seattle Washington. In order to first establish which birds acted as primary tutors, researchers recorded 78 juvenile Song Sparrows and 120 potential tutor sparrows. They then analyzed the recorded songs with something called a spectrogram. Spectrograms are computer-generated graphs that depict audio waves and changes in frequencies, essentially illustrating the different notes of their song in a visual format, much like voice recordings or sheet music. The spectrograms were used to compare a juvenile sparrow’s repertoire to the repertoire of their potential tutors. Based on the similarities in the spectrograms, the primary tutor/tutee relationship was established. Song Sparrow survival was then measured for approximately 6 years by taking a monthly population census.
The field study was designed to test two hypotheses: the mutually beneficial/mutually tolerant hypothesis and the competition hypothesis. The mutually beneficial hypothesis predicts that a cooperative or at least tolerant relationship exists. As a result, a greater degree of song sharing between tutor and tutee means they will survive and coexist longer. Alternatively, the competition hypothesis assumes the two individuals are rivals and as such there would be a negative correlation between song sharing and survival of the tutor.
The data seems to align with the mutually beneficial hypothesis because the more song sharing that took place, the longer birds tended to survive on average. This becomes especially clear when mutual survival is compared to the independent survival of the tutor and the tutee. Song sharing could potentially be an adaptive behavior that has evolved because there are few if any benefits when only one of the individuals survive (Beecher et al. 2020). Learning songs from older members of the population may very well be an intentional interaction that encourages alliances, collaboration, and group cohesion, however, further studies are needed to substantiate these conjectures. Overall, this study investigates if learning is ultimately competitive, as expected with unrelated conspecific relationships. What the study found was that song learning seems to be a cooperative behavior as seen in human communication.
References:
Beecher, M., Akçay, Ç., & Campbell, S. E. (2020). Birdsong learning is mutually beneficial for tutee and tutor in song sparrows. Animal Behaviour, 166, 281-288.
The Editors of Encyclopaedia Britannica [Internet]. Encyclopaedia Britannica. Songbird. [updated 2020, Jan 14; cited 2020, Oct 13]. Available from: https://www.britannica.com/animal/songbird.
