Hawaiian Name: ‘A
The Brown Booby is another wide-ranging seabird, breeding in most tropical and subtropical regions of the Indian, Pacific, and Atlantic Oceans. In Hawaiʻi, the largest colonies are found on Kaʻula Rock and Lehua Islet off the coast of Niʻihau, and Nihoa Island, each with about 500 pairs. Smaller colonies are found on islets off Oʻahu, Kahoʻolawe, and on some of the other Northwestern Hawaiian Islands, but the state-wide breeding population probably does not amount to much more than 1,500 pairs.
Although less common than Red-footed Booby in the Hawaiian Chain, this species is still relatively easy to see at any coastal location on Kauaʻi and Oʻahu, with numbers ranging into the double digits not being out of the ordinary. On Kauaʻi the easiest places to see Brown Boobies are from the beach in the vicinity of Kekaha and PMRF, and Kilauea Point NWR, where they are often seen quite close to shore. Brown Boobies are not unusual to see nearshore on Maui, Molokaʻi, Lanaʻi, and Hawaiʻi. Brown Boobies are present year round in the Hawaiian Chain, although fewer numbers are present from October to December when most individuals are not breeding.
In all cases, Brown Boobies are slightly larger, heftier, and darker brown than any dark Red-footed Booby. Adult Brown Boobies are distinctive with their contrasting white bellies and dark head and back, and yellow bill. However, young Brown Boobies are also brown on the belly and are distinguished from brown Red-footed Boobies by their dark tails (vs. adult brown morph Red-footed Boobies) and darker brown overall coloration.
Although the numbers in Hawaiʻi appear to be relatively stable, Brown Boobies are predated by non-native mammals such as rats and cats, which likely restricts them to nesting on offshore islets. Outside of Hawaiʻi, Brown Boobies are often persecuted as food and are greatly affected by habitat alteration and degredation, predation by non-native mammals, and general colony disturbance.