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Egg rejection based on egg size recognition as a specific strategy against parasitic cuckoos
1Ministry of Education Key Laboratory for Ecology of Tropical Islands, College of Life Sciences, Hainan Normal University, Haikou 571158, China.
Current Zoology
|April 24, 2023
Summary
Chestnut-crowned warblers can recognize and reject larger, non-mimetic cuckoo eggs, even in dim light. This study provides strong evidence for egg size recognition as a specific anti-parasite adaptation in avian hosts.
Area of Science:
- Avian ecology
- Behavioral ecology
- Evolutionary biology
Background:
- Egg recognition is a key host defense against avian brood parasitism.
- Egg size recognition has received less attention and lacks unambiguous evidence as a specific anti-parasite adaptation.
Purpose of the Study:
- To investigate egg size recognition in the chestnut-crowned warbler (Phylloscopus castaniceps) as a defense against the Asian emerald cuckoo (Chrysococcyx maculatus).
- To determine if egg size recognition has evolved as a specific anti-parasite adaptation in this host-parasite system.
Main Methods:
- Conducted experiments using model eggs of varying sizes, colors, and patterns within dark warbler nests.
- Assessed warbler rejection rates of model eggs mimicking cuckoo eggs (larger) versus host eggs (smaller).
- Measured nest illuminance to simulate natural, dim light conditions.
Main Results:
- Warblers rejected 63.6% of model cuckoo eggs (larger size, cuckoo coloration) under dim light conditions.
- Model eggs matching host egg size and coloration were always accepted.
- Cuckoo parasitism rate by non-mimetic, larger eggs was observed at 12.9%.
Conclusions:
- Provides strong evidence that egg size recognition can evolve as a specific anti-parasite adaptation in avian hosts.
- Suggests warbler egg size recognition is a result of balancing the costs of rejecting own eggs versus accepting parasite eggs.
