Cryptic gentes revealed in pallid cuckoos Cuculus pallidus using reflectance spectrophotometry

Area of Science:

• Avian reproductive strategies
• Evolutionary biology
• Behavioral ecology

Background:

• Many cuckoo species exhibit egg mimicry to reduce host rejection.
• Generalist cuckoos parasitizing multiple hosts with diverse egg types face challenges with a single egg morph.
• Some generalist cuckoos have evolved host-specific races (gentes) with distinct egg types.

Purpose of the Study:

• To investigate host-specific egg types in the generalist pallid cuckoo (Cuculus pallidus), which was previously thought to have a uniform egg type.
• To determine if pallid cuckoo eggs mimic the eggs of their various host species.

Main Methods:

• Utilized reflectance spectrophotometry (300-700 nm) to analyze egg coloration.
• Examined museum egg collections to compare pallid cuckoo eggs from different host species.

Main Results:

• Pallid cuckoo egg color varied significantly among four different host species.
• The egg coloration of pallid cuckoos closely matched the egg types of the specific hosts they parasitized.
• These host-specific egg types were not discernible through human observation alone.

Conclusions:

• The pallid cuckoo exhibits undetected host-specific egg types, demonstrating a sophisticated mimicry strategy.
• The existence of these cryptic egg types suggests that host-specific races (gentes) may be more prevalent in cuckoo species than previously recognized.