The Magnificent Frigatebird often nests in mangroves, but also in bushes and even on cactus. It can breed on the ground (del Hoyo et al. 1992). Data reveals it is almost continuously on the wing, with morphology and flight pattern resulting in extremely low costs of foraging, relying on prey driven to the surface by underwater predators such as tuna. Low cost of flight due to extensive use of thermals allows exploitation of tropical waters in which prey is scarce (Weimerskirch et al. 2003). It feeds mainly on flying-fish and squid, but also jellyfish, baby turtles, seabird eggs and chicks, offal and fish scraps (del Hoyo et al. 1992).

This species is distributed on the Pacific and Atlantic coasts of America, from California (U.S.A.) to Ecuador (including the Galapagos), and from Florida to south Brazil. One relict population used to breed at Cape Verde off the coast of Africa, but is now feared extinct (Orta et al. 2018).