National Geographic : 2019 Feb
PHOTO: TUI DE ROY, MINDEN PICTURES EXPLORE | BASIC INSTINCTS MANY A SUITOR puffs out his chest hoping to impress the ladies. But for hue, girth, and sheer musicality, none beats the blimplike bosom on Fregata magnificens, the magnificent frigatebird. During a courtship display, each male seeks to outdo the others with one body part: a red pouch hanging from his throat. When he inflates this gular sac, it balloons into a heartlike shape as tall as he is. Then he clacks his beak, and it resonates in the sac like a drumbeat, a thrumming love call. “You hear it long before you see them,” says Jen Jones of the Galapagos Conservation Trust, who has witnessed displays on the islands. Females that have been gliding overhead land and eye their options. Males may turn up the heat even more with “disco moves, head shakes, or the occasional shimmy,” Jones says. One study (right) says it’s the drumming that gets males the most mates, but the whole show is “absolutely amazing,” Jones says. “A feast for the senses.” —PATRICIA EDMONDS IS HIS IDEA OF SEX APPEAL INFLATED? YES. LITERALLY. HABITAT/RANGE Fregata magnificens chiefly inhabits the Americas’ Pacific and Atlantic coasts and adja- cent islands, from California and Georgia south to Ecuador and Uruguay. CONSERVATION STATUS The International Union for Conservation of Nature ranks the bird “least concern,” but invasive species and habitat loss affect some populations. OTHER FACTS • Frigatebirds stay aloft for months at a time, riding thermal updrafts. They’ll swoop to the ocean’s surface to find food, Jones says, or steal it from other animals: “They’re pirates, basically.” • Ecologists who studied male birds’ courtship moves in Mexico concluded that the sound effects “significantly predict mating success.” Males that drum at lower frequencies—thanks to larger gular sacs—and in quicker, more constant cadences appealed more to females, which may perceive them as more experienced or vigorous, the study says.