Brown Booby, Sula leucogaster

Brown Booby, Sula leucogaster. Photographs, taken in the greater Los Cabos area of Baja California Sur. Uncommon.

Brown Booby, Sula leucogaster. Photograph taken in the greater Zihuatanejo area, Guerrero, March 2018. Photograph courtesy of Ron Woheau, Zihuatanejo.

Brown Booby, Sula leucogaster. Photograph taken in coastal waters off Loreto, Baja California Sur, October 2019.

Brown Booby, Sula leucogaster. Photographs, taken in the greater Los Cabos area of Baja California Sur. November 2020.

Brown Booby, Sula leucogaster, Male. Photograph taken in coastal waters off southern Baja California Sur, October 2020. Photography courtesy of Chip Shapley, Las Barilles, Baja California Sur.

Background and Identification

The Brown Booby, Sula leucogaster, is a member of the Sulidae Family of Boobies and Gannets. The breeding range of this species overlaps significantly with that of the Masked Booby, Sula dactylatra, and the Red-footed Booby, Sula sula. All three of these Booby species may be seen nesting and feeding together in these areas, along with many other seabirds. They roost on rocky islets and shorelines in areas with little or no vegetation and are shallow-water plunge divers with their diet consisting primarily of fish and a limited amount of squid. In Mexico, they are called Bobo Café.

The Brown Booby is mid-sized in stature, measuring 64 cm (2 feet 2 inches) to 76 cm (2 feet 2 inches) in length. Adult Brown Boobies have a dark brown head, back, and upper wings, with a contrasting white belly and underparts. Their beak is sharp and pointed, typically yellow or grayish. They have long, tapered wings and a tail that helps them maneuver while diving for fish. Both males and females look similar, though females are generally larger. Juveniles are uniformly brown and gradually develop the characteristic adult plumage.

Habitat and Geographical Range

Brown Boobies are primarily found in tropical and subtropical oceans worldwide. They prefer coastal waters, islands, and coral reefs where they can find ample food and nesting sites. These birds are expert divers, plunging into the water to catch fish and squid.

Geographically, Brown Boobies have a wide range, including the Atlantic, Pacific, and Indian Oceans. In the Americas, they are commonly found along the coasts of the Gulf of Mexico, the Caribbean Sea, and the Pacific coast from Mexico to South America. They are also present in the central and western Pacific, including the Hawaiian Islands, and parts of the Indian Ocean. In Mexico, they are limited to the coastal regions within the Atlantic Slope in the state of Campeche, and they are found in all waters within the Pacific Slope at elevations below 100 m (330 feet).

Common Misidentifications

Brown Boobies can be confused with other booby species, particularly those within their range. One common look-alike is the Red-footed Booby, Sula sula, which has a similar size and shape but can be distinguished by its red feet and more varied plumage, including white morphs.

Conservation Status

 From a conservation perspective the Brown Booby is currently considered to be of Least Concern with stable, widely distributed populations. Habitat destruction, particularly on nesting islands, poses a significant threat. Human activities such as coastal development, pollution, and disturbance can also negatively affect their populations. Additionally, overfishing can reduce their food supply, leading to decreased breeding success. Conservation efforts for Brown Boobies should focus on protecting their nesting habitats and reducing human disturbances.