Urbanization enhances ornament expression in a common waterbird

Area of Science:

• Avian ecology and evolution
• Urban biology and adaptation
• Animal signaling and communication

Background:

• Visual communication in birds relies heavily on ornaments (plumage and non-plumage) for signaling individual quality.
• Environmental conditions, including urbanization, can modulate ornament expression, but effects on non-plumage ornaments are understudied.

Purpose of the Study:

• To investigate the impact of urbanization on the expression of bare-part (non-plumage) frontal shield size in the Eurasian coot (Fulica atra).
• To explore the relationship between shield size, condition, and behavioral patterns in urban-dwelling coots.

Main Methods:

• Examined frontal shield size across eight Eurasian coot populations experiencing varying degrees of urbanization.
• Conducted long-term monitoring of a single urban population to assess ornament expression in relation to nest site selection, behavior, and reproductive success.

Main Results:

• Found robust evidence that urbanization positively affects frontal shield size in Eurasian coots, with a condition-dependent component.
• Larger shield sizes correlated with bolder nest site selection in more disturbed urban areas with greater food availability.
• No significant associations were found between shield size and nest defense behavior or reproductive performance.

Conclusions:

• This study provides the first evidence for enhanced expression of an unpigmented, non-plumage ornament in urban birds.
• Urbanization's effects on non-plumage quality signaling are complex and species-specific, necessitating further research across diverse avian taxa.