Honors Theses

Date of Award

Spring 5-10-2023

Document Type

Undergraduate Thesis



First Advisor

Lainy B. Day

Second Advisor

Christopher Leary

Third Advisor

Richard Buchholz

Relational Format



Protein needs of non-poultry birds, like Zebra Finches (ZF) are understudied. ZFs consume proteinaceous half-ripe seeds during breeding and chicken eggs are recommended supplements for captive ZFs; but developmental needs are unclear. Eggs contain essential amino acids that impact the “stress” hormone, corticosterone (CORT). Diet and corticosterone influence avian growth and stress management. Juvenile egg-fed ZFs outgrow seed-fed birds. Juvenile egg-supplementation boosts adult male attractiveness due to cheek patch augmentation compared to seed-only birds. Across studies, timing of diet (nestling Vs. fledgling) varies, both sexes have not been included, and simultaneous measures of growth and corticosterone are lacking. We are testing how egg-supplement impacts body growth, check patch size, and baseline and stress-reactive circulating corticosterone levels in male and female ZFs starting at post-fledging nutritional independence (~35 days old). Birds were placed in single-sex cages and fed seed and bread alone or provided egg supplement for 62 days). Daily food intake/cage was measured during the focal study and in an additional experiment controlling for humidity/evaporation. Mass was measured every 5 days, head to beak ~every 15 days, and tarsus once at the end of the study. We predicted that: 1) Egg supplementation increases body growth with larger effects in females than males presuming higher female protein intake; 2) Egg will increase cheek patch size in males; 3) Baseline and reactive corticosterone levels will be higher in no egg than egg birds, with higher corticosterone in females vs. males for reactive stress due to ovarian hormone influence on buffering stress reveal. As predicted, mass increased most in egg females relative to other groups, and no egg birds had increased levels of reactive CORT, while the egg group appeared to buffer this response. Unlike we predicted, baseline CORT levels were similar across all groups, but egg supplements buffered against reactive stress in both sexes. The influence of diet on male cheek patch was side specific with no overall differences between diets. Ours is the first study able to reveal sex differences across these factors, explain how post-fledgling diet impacts body condition, sexual attractiveness via cheek patch size, and inform feeding practices for captive finches.

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Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

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