Notes: Cf.
Lesser Frigatebird: larger, longer bill, lacks white axilliary spurs.
Male: all black; red gular sac in breeding. Female: pale grey/white
throat; black belly reaching well forward. Nominate minor female
in NW Aust has pink orbital ring. Ssp palmerstoni female in NE Aust has
blue orbital ring. Orbital ring colour may also vary w. location.
Juvenile: buff hood, elliptical white belly patch. Known as "Pirates of
the Sea" as they rob other birds of their catch.