Although some researchers argue that turn-taking — in all forms, but particularly with respect to communication — is a uniquely human skill (Melis et al., 2016), elements of such behavior are common in many birds. For example, almost all songbirds use what is termed “countersinging” to defend their territories, their mates, and/or their nests.
Countersinging, depending on the species, shows an extreme range of flexibility — from exactly matching the song of the intruding bird to evaluating and singing one of several different songs in a neighbor’s repertoire, with each response having a different meaning (see chapters in Marler & Slabbekoorn, 2004). If the species has a number of songs that are commonly sung, simply singing a song in the neighbor’s repertoire acts as a somewhat gentle reminder for the neighbor to remain “neighborly”; matching exactly is reserved for times when the neighbor crosses the territorial boundary and is perceived as a threat.
Somewhat more specialized are duets, which are generally used between mated pairs, and have been found in species from wrens to parrots. The flexibility again varies, depending on the species, and the functions can be manifold (Dahlin & Benedict, 2014) — from a mated pair using their duet to countersing with a pair of invaders in order to defend their territory, to a pair mutually singing to cement their bond. Duets often contain elements that are used exclusively with a mate so that pairs can locate each other aurally in dense foliage.
My own research has been based on Todt’s (1975) initial finding that Grey parrots will adapt their species-specific turn-taking interactions to interspecies communication. He started by training birds, using the modeling technique I’ve described previously, to interact with humans in short dialogues. For example, the human would say “You are my…” and the parrot would respond “…good little parrot.” My students and I adapted and expanded his technique, and over the course of 40 years of study, I found that I could use interspecies turn-taking to examine Grey parrot intelligence.
My parrots would indeed respond flexibly to various human queries (e.g., “What’s this?”, “What color?”, “What shape?”, “How many?”, “What’s same/different?” etc.), often with respect to the same pair of stimuli (see photo), providing evidence that they processed each question, determined the meaning of the question and the category involved, and then chose the appropriate, specific response (e.g., Pepperberg, 1999).
Although my students and I did not directly focus on the issue of turn-taking dialogues or instances in which the birds initiated vocal interactions, and thus did not consistently record occurrences of such behavior, several anecdotes were documented. Birds questioned experimenters for information about novel items (e.g., asking about colors, shapes, and object labels); the birds expected answers and repeated their requests if no responses were forthcoming. Alex, for example, learned the label “carrot” by asking what we were eating, the color “orange” by asking the color of the carrot, and “gray” by asking “What color?” when he saw himself in a mirror.
Some interactions more closely resembled their species-specific duets. So, for example, we never were really sure if Alex understood exactly what all the sentences meant in our “good night routine,” where the elements and roles of the speakers varied nightly (either one of us could say, “I’m gonna go eat dinner,” “You be good,” “I’ll see you tomorrow,” “I love you,” etc.) , but the dialogue definitely was something that reassured him that our leave-taking was a normal part of the daily routine.
On occasion, Alex used turn-taking to further clarify interactions, so as not only to request a particular food, but also something very specific about that food. One time he kept stating “Want grape!” but then consistently tossed the fruit we gave him to the floor. Finally, he looked at us (in a parrot version of what could very easily have be interpreted as disgust) and said “PURPLE!” We had been giving him green grapes that day.
Interestingly, turn-taking was also demonstrated with humans in a physical task to test for cooperation, where Griffin and a student took turns choosing cups as “tokens” (Péron et al., 2014). Choice of a purple cup meant no one got anything, choice of a pink cup meant the chooser kept the nut, choice of an orange cup meant the other individual got the nut, and choice of green meant both got nuts. The human was told to replicate whatever Griffin did, and Griffin very quickly learned that the green cup was the best choice so that everyone got fed on every turn!
As I’ve said many times before, my parrots could not be said to have acquired a complexity of interaction in any way comparable to the richness of human language. Nonetheless, they did use what speech they had acquired in order to demonstrate that they understood and could referentially use certain elements of communication once thought beyond the reach of nonhumans.