Anomalous Gular Pouch Displays in Female Lesser (<i>Fregata ariel</i>) and Christmas Island Frigatebirds (<i>F. andrewsi</i>)

ABSTRACT Sexual dimorphism defines frigatebird (Fregatidae) courtship, with males inflating bright red gular pouches to attract mates. We document rare cases of female gular pouch inflation in Lesser ( Fregata ariel ) and Christmas Island Frigatebirds ( F. andrewsi ). This previously undocumented behavior likely does not serve an adaptive function but may reflect physiological anomalies (hyperandrogenism) or endocrine‐disrupting chemicals, warranting further investigation.