Nesting behaviour influences species-specific gas exchange across avian eggshells

Area of Science:

• Evolutionary Biology
• Avian Ecology
• Physiological Ecology

Background:

• Controlled gas exchange through avian eggshells is crucial for embryonic development.
• Water vapour conductance (G(H2O)) regulates water loss, preventing desiccation and ensuring hatching success.
• Sub-optimal gas exchange negatively impacts avian embryo development and hatching rates.

Purpose of the Study:

• To investigate the evolutionary associations between eggshell G(H2O) and avian life-history traits, nest parameters, and egg characteristics.
• To understand how G(H2O) variation evolves to maintain optimal water loss across diverse nesting environments.

Main Methods:

• Measured eggshell gas exchange (G(H2O)) in 151 British breeding bird species.
• Utilized phylogenetically controlled, general linear models to analyze relationships between G(H2O) and predictor variables.
• Assessed 17 life-history traits, ecological nest parameters, and physical egg characteristics.

Main Results:

• Eggshell G(H2O) was significantly associated with two key factors: wet-incubating parent and nest type.
• Species with parents returning to the nest with wet plumage exhibited higher G(H2O).
• Species nesting in ground burrows, cliffs, and arboreal cups showed significantly higher G(H2O) compared to those in open nests or tree cavities.

Conclusions:

• Avian eggshell G(H2O) evolves in response to parental and nesting behaviors, influencing nest microclimate humidity.
• Higher G(H2O) in certain species compensates for increased nest humidity caused by wet plumage or confined nesting structures.
• Observed G(H2O) differences result from a combination of evolutionary history and species-specific ecological adaptations.