While captive birds are famous for mimicking human speech, researchers from the University of Pittsburgh at Johnstown have found that wild Yellow-naped Amazon parrots use a sophisticated form of syntax when communicating with their mates.
In a study published in the Journal of Avian Biology, biologist Christine Dahlin and her team decoded the “warble duets” of these critically endangered birds, revealing a communication system far more complex than previously understood.
“Ultimately I really want to understand how these birds are communicating in the wild,” said Dahlin. “I want to know what they are saying, and how they are saying it.”
Aggressive grammar
The researchers focused on “warble duets” — loud, rapid vocalisations used by mated pairs during territory disputes. Unlike standard calls, these duets sound “very irate,” occurring when birds are “getting in each other’s faces”.
To analyse the chaos of these calls, the team employed an unusual tool: software designed for analysing human literature.
Suggested by undergraduate student Owen Small, the program Voyant Tools is typically used to study texts in humanities classes. When applied to the bird calls, the software identified “collocates” — clusters of sounds that are frequently paired together, much like the words “eat” and “food” in human language.
“The results show the parallels between these complex signals the birds are giving and our own language,” Dahlin said.
Decisions, not noise
The study identified a lexicon of 36 distinct call types within the warble duets, far more than the four types found in standard duets. Despite this variety, the birds adhered to strict logic, with the team uncovering more than 20 syntactic rules governing the sequence of sounds.
Crucially, there was very little repetition, suggesting the birds were not simply making noise but engaging in an “elaborate calculus” and making split-second decisions in coordination with their partners.
“They are not simply throwing random notes around,” Dahlin explained. “They’re making multiple decisions… All of this is happening very rapidly.”
