Emlen, S. T. & P. H. Wrege, 2004. Size dimorphism, intrasexual competition and sexual selection in Wattled Jacana (Jacana jacana) a sex-role reversed shorebird in Panama. The Auk, Apr 2004.
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Abstract - We studied sexual size dimorphism, intrasexual competition, and sexual selection in an individually marked population of Wattled Jacanas (Jacana jacana) in the Republic of Panama.
Males are the sole incubators of eggs (28-day incubation) and primary providers of chick care (50-60 days). Females were 48% heavier than, and behaviorally dominant over, males. Females also showed greater development of secondary sexual characters (fleshy facial ornamentation and wing spurs) than males.
Both sexes defended territories throughout the year against same-sex conspecifics. Competition for territorial space was intense, and many individuals of both sexes did not become breeders. Resident females further competed with one another to accumulate multiple mates, resulting in a mating system of simultaneous polyandry.
Female and male residents (territory holders) were larger, heavier, and more ornamented than adult floaters of the same sex. Larger and heavier females also had more mates than smaller females. Body size was thus a critical predictor of success in intrasexual competition for territories (both sexes) and for mates (females).
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About N. Sivasothi
Sivasothi is lecturing Biodiversity, Ecology, Structure and Function, Marine Biology and Animal Behaviour with the Department of Biological Sciences.
His interests include otters, mangroves, museum databases, coastal ecology, tree-climbing crabs and conservation of biodiversity.
He is also the national coordinator of the International Coastal Cleanup Singapore and Toddycats! Volunteers of the Raffles Museum of Biodiversity Research, NUS.