Age-specific mortality, pre- to post-fledging carryover effects, and the timing of fledging in altricial songbirds

Evidence accumulated over recent decades has implicated age-specific mortality as a critical factor shaping life histories, particularly with respect to the mortality of dependent offspring. Altricial songbirds provide a practical system to examine associations among variation in life histories and offspring mortality as nest and post-fledging account for the vast majority of offspring mortalities. My research examined associations between juvenile mortality and traits (morphological and behavioral) across the nesting and post-fledging period in a community of songbirds to provide greater insight into how age-specific mortality shapes avian ecology and life history evolution. Specifically, my research sought to (1) test for potential pre- to post-fledging carryover effects under a morphology-performance-fitness paradigm; (2) evaluate nesting and post-fledging survival rates to provide a greater understanding as to when and why juvenile songbirds leave the nest; and (3) determine if carryover effects occur in brood parasitic cowbirds. I found evidence for pre- to post-fledging carryover effects of wing development in all species I examined, with individuals with less developed wings exhibiting poorer flight ability and experiencing higher rates of mortality after fledging. I also found that carryover effects operating at the species level ultimately help shape patterns of life-history variation among species; species with higher rates of nest predation had shorter nestling periods, fledged young with less developed wings, and exhibited higher rates of mortality. Additionally, these carryover effects translated to and have the potential to inform host quality and selection in the brood parasitic Brown-headed Cowbird (Molothrus ater). Lastly, my comparisons of nesting and post-fledging survival suggest that parent-offspring conflict mediates the timing of fledging across songbird species. Ultimately, my results demonstrate the importance of age-specific mortality in driving life-history variation among songbirds.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Natural Res & Env Sciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2021

Author dc:creator

• Jones, Todd Michael

Contributors dc:contributor

• Ward, Michael P
• Brawn, Jeffrey D
• Benson, Thomas J
• Hauber, Mark E

• post-fledging
• songbirds
• carryover effects
• parent-offspring conflict
• brood parasites
• cowbirds
• fledging
• wing development

Statement dc:rights

• © 2021 Todd Michael Jones

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/110426

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/110426