Date of Award
Summer 2025
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Biology
First Advisor
Alfred Mead
Second Advisor
Dominic DeSantis
Third Advisor
Matt Milnes
Abstract
Rising global temperatures due to climate change have caused declines in many bird species, primarily because temperature is a primary factor in nest site selection and nest success. For example, temperatures exceeding 42°C can have reproductive consequences for nesting females during the incubation stage, including smaller clutch size, low hatch rates, and a shorter incubation period. Secondary cavity nesting birds such as the Eastern Bluebird are particularly vulnerable as common occupants of nest boxes, which are often warmer inside than the outside ambient temperature. We monitored 67 Eastern Bluebird nest boxes at two sites in central Georgia during the bluebird breeding season from 2022-2024. Each nest box contained data loggers on the inside of the nest box that recorded temperature every hour. We examined the relationships between two temperature variables (average daily high nest temperature and the number of hours spent at or above 42°C) and nest success variables (clutch size, hatch rate, incubation days) using generalized linear models. Clutch size declines were significantly associated with increases in average daily high temperature and hatch rates were significantly associated with hours at or above 42°C, which could be due to both embryonic physiological complications and adult behavioral adjustments that lead to delayed or halted embryonic development in the egg, thus reducing the number of fledges per nest. Incubation duration was not associated with either of our temperature variables. Successful management practices for secondary cavity nesting birds will require temperature mitigation and predator deterrence techniques as global temperatures continue to rise.
Recommended Citation
Gordon, Mathew; Stumpf, Katie J.; and Powell, Wayne, "THE IMPACTS OF NEST BOX TEMPERATURE ON EASTERN BLUEBIRD (SIALIA SIALIS) CLUTCH SIZE, HATCH RATES, AND INCUBATION DURATION IN CENTRAL GEORGIA" (2025). Biology Theses. 45.
https://kb.gcsu.edu/biology/45