Theses and Dissertations

Date of Award


Document Type


Degree Name

Master of Science (MS)



First Advisor

Dr. Karl Berg

Second Advisor

Dr. Julie Mustard

Third Advisor

Dr. Robert Dearth


The stress axis of the endocrine system allows for animals to respond to environmental stressors in contextually appropriate ways. Elevated levels of the stress hormone corticosterone (CORT) in male songbirds can result in compromised song learning ability. Parrots form a sister group to songbirds, but it is unknown whether CORT affects vocal development in parrots. The goal of this study was to assess the effects of CORT supplements in green-rumped parrotlets (Forpus passerinus), a free-ranging parrot species in Venezuela. Bouts of vocal babbling were extracted from nest box videos and analyzed. CORT supplementation resulted in differences in babbling vocal production, including peak frequency average slope (p<.0001), inflection points (p<.0001), and syllable duration (p<.0001). Treatment predicted variation in repertoire size but was not significant (p=0.51). Despite differences in stress axis maturation, parrots show some similar responses to early CORT supplementation as songbirds.


Copyright 2021 Celia McLean. All Rights Reserved.