Incubation temperature impacts growth, physiology and survival in nestlings of an open-cup nesting passerine

Early-life conditions can have important implications for somatic and physiological development, and later life survival. For oviparous species, embryonic development occurs wholly within the egg. During this stage, there is good evidence that egg resources such as lipid and protein content and maternal hormones play a critical role in development. Much less is known, however, about the role of incubation temperature in shaping the phenotype. Among species in which one or both parents incubate, there is the possibility that changes in incubation behavior on the part of the parent(s) can impact the developing offspring. The vast majority of birds require bird-egg contact during incubation to maintain an appropriate environment for embryonic development. Therefore, understanding the ways in which incubation temperature influences variation in nestling growth and physiological development as well as survival may be of critical importance to bird conservation. I examined how variation in incubation temperature influences key aspects of nestling development in American robins (Turdus migratorius). Specifically, I sought to address whether incubation temperature influences (1) hatching success, (2) nestling growth rate and three key morphological characteristics, (3) development of the Hypothalamic-Pituitary-Adrenal (HPA) axis and aspects of innate immune defenses in nestling robins, as well as associations between HPA axis activity and immune activity, and (4) nestling survival. From March to August of 2015 and 2016, I worked in a mixed coniferous tree farm in central Illinois, USA, and tracked growth, development of the HPA axis (responsible for stress hormone production, corticosterone) and innate immunity, and survival of nestling robins that were incubated as eggs in one of three temperature categories: 36.1 °C, 37.8 °C, and Naturally incubated. Hatched nestlings from the experimental categories were fostered to same-age nests and monitored throughout the nestling period to determine fate. On days 7 and 10 post-hatch, I measured mass and tarsus length and collected blood samples from experimentally incubated nestlings and one foster nest-mate (Naturally incubated). I collected data from 339 nests and 85 artificially incubated nestlings. I found that nestlings from Low and Optimal incubation categories had lower mass and shorter tarsi, significant reductions in survival, and increased corticosterone concentration. I found no effect of incubation category on immune function, and no significant relationships between corticosterone concentration and innate immune function in nestling robins. My results suggest that incubation temperature can influence subsequent nestling growth, physiology, and survival. This research suggests that factors influencing incubation temperature are important for the fitness of nestlings. Thus, environmental disturbances that disrupt incubation may have population-level impacts. Collectively, my research adds to the growing body of literature suggesting the importance of sublethal stressors (e.g. reduced incubation temperature) on fitness and population dynamics and highlights the importance of these stressors in leading to such effects on nestling survival and development.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Natural Res & Env Sciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2017

Author dc:creator

• Ospina, Emilie Ann

Contributors dc:contributor

• Benson, Thomas J.
• Ward, Michael P.

• Early life experiences
• Incubation
• Maternal effects

Statement dc:rights

• Copyright 2017 Emilie Ann Ospina

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/97488

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/97488