INTELLECTUAL MERIT

The main outcome of this project is the first characterization of the vocal babbling stage in development of a parrot species. In human infants vocal babbling is a critical yet poorly understood stage in language and brain development but has mainly been studied in animal models in which only males babble and often in captivity. Parrots are the most prolific of non-human vocal imitators and the most popular pet bird on Earth, but this stage in vocal development had curiously gone unnoticed in the 360+ parrot species. Our work has revealed that babbling in parrots, unlike most animal models, occurs in both sexes during an earlier stage in physiological development and one more akin to human infant babbling (Fig 1; Berg et al. 2019, J. Exp. Zool.). Whereas other animal models show babbling occurs in males at puberty owing to surges in male gonadal steroids, our work is showing that parrot babbling is modulated by corticosteroids (Fig 2; Eggleston et al. in-review, Mclean et al. in-prep), and a part of the endocrine system that becomes functional prior to the babbling stage in human infants and long before puberty. Corticosteroids are produced in response to many challenging and stressful scenarios, such as disease, hunger, sibling competition and learning of complex communication systems of adults. Compromised stress responsiveness is implicated in speech pathologies, such as Autism Spectrum Disorder, which can obliterate the babbling phase, however, details are lacking and new animal models with relevant life history and physiological characteristics are needed. Human infant babbling is also curious in that its precise function and influence on later social cognitive function is subject to debate. Vocal babbling is often referred to as "vocal play" and both humans and parrots also have elaborate and extended periods of social play that can emeliorate stress. However, little is known about how social play behaviors might be linked to vocal imitation. We showed that parrots spend many waking hours engaged in social play with siblings, and that the quantity and quality of playmates extends the onset to vocal imitation (Fig. 3; Arellano, et al. in-review). Play and exploratory phases in development can coincide with a neural pruning process in late development regions of the brain, that tailor neuroendocrine systems to prevailing social environments. Thus, parrot social play with siblings could be implicated in late developing brain regions that control vocal babbling. Natural human language development often involves vocal interactions with mixed-aged siblings and close kin and non-kin, as well as related and unrelated adults. Relevant animal models are again needed to track the long-term consequences of early formative experiences in nature. Field work occurred entirely in a wild population in Venezuela. During the last 33 years, the project has permanently marked over 9,000 individual parrots and meticulously quantified annual survival and reproductive output at the field site. Babbling and play behaviors above were quantified from a HD audio-video collection that now spans 12,000 hours during development of 600 nestlings over the last decade. The long-term study thus allows us to collect survival and lifetime reproductive success of individuals studied and manipulated as nestlings years earlier. This information is critical for understanding the adaptive function of vocal babbling.

BROADER IMPACTS

During the project period we participated in the largest assessment to date of how birds are adapting to climate change (Radchuk et al. 2019 Nature. Commun.). Results indicate that birds are adapting behaviorally, but not morphologically to climate trends. Our work may have implications for veterinarian treatment of stress-related illness' in pet parrots, as well as parrots that live in zoos. Self-mutilation via feather-plucking in pet parrots is widespread and thought to be related to social and psychological stressors. Results may also have implications for animal husbandry programs aimed at reproducing parrots in captivity, either to lessen the demand for the trafficking of wild parrots or to reintroduce parrots into areas where they have been extirpating by human influences. The project provided training and experience in ecological population monitoring, behavioral and endocrine sampling to 13 Venezuelan biologists. Based at one of the largest predominantly Hispanic-serving public institutions of higher learning in the U.S. the project provided, training, educational and research opportunities to four graduate, twenty-one undergraduate, two high school and one middle school student. The project increased public awareness of the project outcomes through features in several local television and newspaper agencies; interviews with Texas Public Radio, Texas Climate Report, Radio Lab (NPR), National Geographic Magazine, Science magazine, Oxford Scientific Films and the lab website. Mimicking our nest box design in Venezuela, we helped a local eagle scout candidate construct a series of nest boxes for a globally endangered and heavily trafficked parrot endemic to Northeast Mexico and extreme South Texas and that ranges freely on our campus (Fig. 4).

Last Modified: 09/01/2021
Modified by: Karl Berg