With a wingspan over two meters and a forked tail, the frigatebird hangs over the sea off Cabo almost without flapping. It almost never lands on the water, so it watches for whatever pushes fish to the surface, and so do the captains watching it.
A big, all-dark seabird with long, angular wings, a deeply forked tail often held closed in a point, and a long bill with a hooked tip. Adult males are all black, with a red throat pouch they inflate like a balloon in the breeding season. Females have a white chest and a dark head, and are bigger than males. Juveniles have a white head and belly that darken as they age.
Magnificent frigatebirds live along tropical and subtropical coasts and islands of the Americas, foraging far offshore, along the coast and in shallow lagoons. In Baja California Sur they nest in colonies on Espíritu Santo, in the Gulf of California, and on Isla Santa Margarita and the Magdalena lagoon complex on the Pacific side. They lay a single egg in a flimsy stick platform on low trees or shrubs.
They eat mainly fish, including flying fish and tuna, plus squid, which they grab from the surface without getting wet, and they also feed on fishing waste. Breeding is unusually slow: incubation takes about 53 to 61 days and the chick stays in the nest 150 to 185 days. Males leave when the chick is three to four months old, and the female keeps feeding it for up to a year.
EEG recordings of great frigatebirds, a close relative, flying for up to 10 days showed they sleep in flight in bursts of about 11 seconds, often with one half of the brain at a time. In the air they slept only about 41 minutes a day, against more than half the time on land.
Source ↗Satellite-tracked great frigatebirds from the Mozambique Channel stayed airborne for over two months, climbing to 3,000–4,000 m inside cumulus clouds to ride the updrafts.
Source ↗Unlike other seabirds, frigatebirds lack waterproof feathers, so they rarely land on the water even though they have webbed feet. Their legs are so short they can barely walk on land either.
Source ↗On Isla Isabel, Nayarit, frigatebirds chased blue-footed boobies to make them drop their catch. Most attacks were by females and young birds, only about 6% succeeded, and group chases worked three times better than solo ones.
Source ↗A male tagged in Baja California Sur flew 23,312 km between May 7 and October 10, 2017. Males leave the colony in early summer and return in autumn for the next breeding season.
Source ↗At Estero Las Tijeras, in the Magdalena lagoon complex, nesting pairs fell from 20,117 in 1986–87 to 532 in 2015. Researchers estimate more than 18,000 pairs have been lost from Baja California Sur’s colonies.
Source ↗Out in the open ocean, tropical seabirds depend on tunas and other predators that drive small fish to the surface; researchers call feeding in flocks over tunas the most important foraging strategy for tropical seabirds. Frigatebirds are often found over dolphins, tuna or other predatory fish doing exactly that, which is why captains keep an eye on the sky.
Captains’ rules of thumb, as told to Marlin Magazine: one or two frigates circling high over one spot are watching something, maybe a marlin swimming deep or a school of bait; birds dropping low and swooping at the waves mean bait is on the surface, often pushed up by marlin, sailfish or dorado. Some captains find them a better sign of dorado than of blue marlin, while Pacific captains count them as a good sign for both. Frigatebirds also scavenge fishing waste, so a bird hanging over a fleet isn’t always over fish.
| Mexico (NOM-059) | Not listed as a species at risk (2019 update) |
|---|---|
| IUCN Red List | Least Concern |
| Partners in Flight | Yellow Watch List; about 113,000 breeding birds worldwide |
| Nearest colonies to Cabo | Espíritu Santo (Gulf of California) and Isla Santa Margarita (Pacific) |
The great frigatebird nests on the Revillagigedo Islands, far south of Baja, and is rarely confirmed near the peninsula; adult males show a pale bar across the upper wing, and females have a pale throat, while magnificent females have a clean all-dark head. Boobies plunge-dive and rest on the water, and so do gulls; a frigatebird almost never touches down on the sea and steals or skims its food instead.
Because they feed on fish pushed to the surface by tuna, dolphins and other predators. Birds circling or dropping low can point to bait, dorado or billfish below.
Rarely. Its feathers aren’t waterproof, so it catches food from the surface without getting wet or steals it from other birds in the air.
Adult males are all black, with a red throat pouch in breeding season. Females have a white chest and are larger. Young birds have white heads.
Top illustration: Top Anglers. Photos: iNaturalist contributors, credited on each photo.
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