Year of Award


Document Type


Degree Type

Master of Science (MS)

Degree Name

Wildlife Biology

Department or School/College

College of Forestry and Conservation

Committee Chair

Thomas E. Martin


breeding biology, egg temperature, embryonic temperature, incubation, life history strategy, nest attentiveness, reproductive strategy


University of Montana


Paternal care has been neglected in behavioral studies because it is rare among most animals. Birds express wide variation in male care across a broad life-history gradient, but such variation among species remains poorly explored. At the same time, contributions of male assistance with incubation have been largely overlooked with the assumption that incubation is a time of low parental energy expenditure. We compared male versus female biparental incubation effort between two tropical antbird species in the northern Andes of Venezuela. We found that males and females apportion reproductive effort differently between these two species, but that male contributions of time and incubation effort were generally greater than for north temperate species which exhibit different life-history strategies. Males spent an equal or greater amount of time incubating, yet maintained lower egg temperatures than females during different age-specific stages of the incubation period. Despite sex differences in incubation temperatures, males rewarmed cold clutches at similar rates to females suggesting similar sex-specific physiological incubation abilities. For the first time in a nidicolous species, we found that temperatures experienced by developing embryos increased with age of eggs independent of male and female time spent on the nest. Our results suggest that males may benefit embryo development by minimizing time eggs experience cold temperatures during female absences, and concurrently benefit female physiological condition for future nesting efforts. Lastly, we report standardized measures of reproductive traits in these two endemic tropical species in hope of improving data collection efforts outside of North America. Standardized measures of reproductive traits are essential for improving our understanding of reproductive biology and avian life-history evolution among different regions of the world. The Tropical Andes are among one of the most species-rich areas in the world and represent an area of critical conservation concern. Yet, for many endemic taxa inhabiting this region even basic descriptions of reproductive traits are entirely absent. This study extends the range of variation in reproductive strategies among a broader range of species among geographical regions.



© Copyright 2008 Brian A. Schwartz