What makes an egg shiny?

Bird eggs exhibit a wide diversity of colors and patterns that serve key functions, including predator avoidance, parasite interactions, parental investment, and protection from light. Eggshell reflectance extends beyond visible coloration into ultraviolet (UV) and near-infrared (NIR) wavelengths, with variation in these ranges comparable to that in visible light. Yet, the mechanisms driving non-visible reflectance remain poorly understood. This project will investigate which eggshell properties influence variation in UV and NIR reflectance by measuring a large sample of eggs from three species with different nesting ecologies and broad distributions. Using optical and electron microscopy, we will identify the mechanisms underlying reflectance and apply statistical analyses to determine the degree of plasticity in egg traits and the ecological factors shaping eggshell coloration and its evolution.

This project has two objectives:

• To quantify intraspecific variation in egg reflectance in birds
• To determine the mechanistic determinants of egg reflectance and their associations with ecological and life-history factors.

The student will research egg specimens, previously collected by the supervisor, from guineafowl, jackdaws and ducks. She/he will measure egg reflectance in the ultraviolet, visible and near-infrared ranges using spectrophotometry. They will learn to prepare samples for microscopy visualization and use optical and electron microscopy to analyze and quantify aspects of eggshell morphology.

The student will then perform statistical analyses on the data collected.

Reflectance curve from an egg obtained through spectrophotometry.

The student will work for a duration of 6 months on data collection and analyses. Particular interest in ornithology, functional morphology and trait evolution is preferred.

The project is suitable for one master student and one bachelor student.