DELAYED PLUMAGE MATURATION IN PASSERINE BIRDS: RELIABLE SIGNALING BY SUBORDINATE MALES?

Area of Science:

• Ornithology
• Behavioral Ecology
• Evolutionary Biology

Background:

• Delayed plumage maturation (DPM) in passerine birds is explained by three hypotheses: Cryptic, Female Mimicry, and Winter Adaptation.
• These hypotheses conflate proximate functions of plumage with selective mechanisms driving them.

Purpose of the Study:

• To critically evaluate existing hypotheses for DPM in passerine birds.
• To propose and test a new Status Signaling Hypothesis (SSH) for DPM.

Main Methods:

• Review and deconstruct existing hypotheses on DPM.
• Analyze the relationship between territory type and the prevalence of DPM using literature data.

Main Results:

• Existing hypotheses for DPM lack strong supporting evidence.
• The Status Signaling Hypothesis (SSH) proposes dull plumage in second-year (SY) males signals subordinate status.
• DPM is significantly more common in species with simple nesting territories, supporting the SSH.

Conclusions:

• Dull plumage in SY males serves as a reliable signal of subordinate status.
• Female choice for brighter males drives the evolution of subordinate status signaling.
• DPM is favored in species where males defend simple territories, as it facilitates subordinate SY males' integration and reduces aggression.