Just not paying attention I guess. The presence of the metacarpal spur is not a secondary sexual characteristic. Both sexes have them, and all year round. Visible only when the underwing is visible. They would appear to be involved as a visible deterrent in threat displays (easily visible yellow spur against the dark brown underwing). Possibly also somehow used by the male birds when tucking the eggs (and later the young) under the wing while incubating. Genus Jacana is, by the way, not the only genus in the Family Jacanidae to have them as they are present also in Hydrophasianus.
Oriental Bird Club
Neotropical Bird Club
Last edited by cuckooroller : Wednesday 5th July 2006 at 06:02.