Causes and consequences of timing of ornamental plumage molt and courtship in captive ruff sandpipers (Calidris pugnax)

Abstract

Ruff sandpipers (Calidris pugnax) are medium-sized Eurasian shorebirds extraordinary for their sexual dimorphism and lek breeding system. Ruffs possess a unique genetic polymorphism for male courtship behavior with three stable male morphs: Independents, Satellites, and Faeders. Independent males are identified by their darker ruff plumage, are dominant, and will defend their court on a lek. Satellite males have predominantly white ruff plumage and are tolerated on the courts of Independents and co-display alongside them on the lek. Faeders, the third male morph, are female mimics that do not display but are tolerated on courts and attempt to sneak matings.

To document ruff molt progression in male ruff sandpipers, I noted the date that each male’s ruff and head tufts were fully grown and the date that each male’s ruff or head tufts began thinning, as applicable. Observations were made four days per week between April and June to identify the onset and duration (in days) of courtship behavior for each of the nine males. Our results will help us gain a deeper understanding of the intrinsic and extrinsic factors that trigger molt and courtship behaviors and lead to improved captive breeding programs for this species.