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Pigment concentrations only partially predict avian eggshell colour mimicry in a polymorphic host-brood parasite
Daniel Hanley1, Mark E Hauber2, Mandë Holford3,4,5
1Department of Biology, George Mason University, Fairfax, VA, USA.
Biology Letters
|June 10, 2025
Summary
Cuckoo finches mimic host eggs using similar pigments but higher concentrations. Pigment proportions predict blue egg colors, but not brown, revealing complex avian eggshell coloration mechanisms.
Area of Science:
- Evolutionary Biology
- Animal Behavior
- Biochemistry
Background:
- Avian brood parasitism involves egg mimicry, driving co-evolutionary dynamics between hosts and parasites.
- Research has primarily examined host responses to mimicry, with less focus on the proximate mechanisms of eggshell coloration in parasites.
Purpose of the Study:
- To investigate the chemical and visual mechanisms underlying the diverse eggshell coloration in the cuckoo finch (Anomalospiza imberbis) and its host, the tawny-flanked prinia (Prinia subflava).
- To understand how pigment composition and concentration contribute to perceived eggshell colors in this brood parasite-host system.
Main Methods:
- Chemical analysis of eggshell pigments (biliverdin and protoporphyrin).
- Avian visual modeling to assess perceived eggshell coloration.
- Statistical analysis to correlate pigment composition with eggshell color variation.
Main Results:
- Both cuckoo finches and prinia incorporate similar proportions of biliverdin and protoporphyrin, but cuckoo finches deposit higher pigment concentrations.
- Pigment proportions accurately predicted eggshell color in bluer eggs but not in browner eggs.
- The relationship between eggshell chemistry and perceived color is complex and varies within and between species.
Conclusions:
- Cuckoo finches achieve eggshell color mimicry through variations in pigment deposition concentration, not just proportion.
- The role of brown pigments in eggshell coloration may extend beyond color, potentially involving maculation or structural integrity.
- This study highlights the intricate interplay between eggshell chemistry, pigment variation, and avian visual perception in co-evolutionary systems.
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