Vocal babbling in a wild parrot shows life history and endocrine affinities with human infants

Abstract

Prelinguistic babbling is a critical phase in infant language development and is best understood in temperate songbirds where it occurs primarily in males at reproductive maturity and is modulated by sex steroids. Parrots of both sexes are icons of tropical vocal plasticity, but vocal babbling is unreported in this group and whether the endocrine system is involved is unknown. Here we show that vocal babbling is widespread in a wild parrot population in Venezuela, ensues in both sexes during the nestling stage, occurs amidst a captive audience of mixed-aged siblings, and is modulated by corticosteroids. Spectrographic analysis and machine learning found phoneme diversity and combinatorial capacity increased precipitously for the first week, thereafter, crystalizing into a smaller repertoire, consistent with the selective attrition model of language development. Corticosterone-treated nestlings differed from unmanipulated birds and sham controls in several acoustic properties and crystallized a larger repertoire post-treatment. Our findings indicate babbling occurs during an early life-history stage in which corticosteroids help catalyse the transition from a universal learning programme to one finely tuned for the prevailing ecological environment, a potentially convergent scenario in human prelinguistic development.

Eviction-driven infanticide and sexually selected adoption and infanticide in a neotropical parrot

“…We never detected aggressive interactions between nestlings during tens of thousands of nest checks and extensive handling of nestlings. Moreover, we never observed nestlings to vigorously bite or attack each other during ~2,000 h of video observations inside boxes at 51 nests as part of our studies of vocal development ( 59 – 62 ). Camcorders recorded continuously, beginning between 0700 to 0900 h and lasting 1 to 3 h. Filming was conducted daily after the female parent ceased incubation and continued until the last nestling fledged from the nest or the nest failed.…”

What We (Don’t) Know about Parrot Welfare: A Systematic Literature Review

“…Today, these birds, belonging to the order Psittaciformes (2), are one of the most popular companion animals after dogs and cats (3)(4)(5)(6). Such popularity can be attributed to their bright and colourful plumages, but more importantly to their unique learning abilities which are comparable to those of human toddlers (7)(8)(9)(10). Parrots, supported by large and neuron-rich forebrains (11,12), can use and even manufacture tools (13)(14)(15)(16), think economically (17,18), succeed in problem solving, reasoning and planning tasks (19), and even remember their own past actions (20), an important prerequisite for self-awareness.…”