Red-footed Booby (Sula sula)
Adult Red-footed Booby, Lehua Islet (Photo by Eric Vanderwerf)
Like the Brown Booby, Red-footed Boobies are found almost worldwide in tropical and subtropical oceans where it nests on oceanic islands and associated islets. The Red-footed Booby is the most common booby species in Hawaiian waters, with about 7,500 breeding pairs at colonies in most of the Northwestern Hawaiian Islands, and about 5,000 breeding pairs divided between colonies on Ka'ula Rock, Lehua Islet, Kaua'i, and O'ahu. The largest of these colonies is at Kilauea Point NWR, which is the only colony of Red-footed Boobies on Kaua'i. There, the colony established in the 1960's and has expanded rapidly to now include more than 2,000 breeding pairs.
In the Southeastern Hawaiian Islands, Red-footed Boobies breed year round, whereas in the Northwestern Hawaiian islands, breeding is largely restricted to spring and summer. Breeding sites are largely restricted by the availability of bushes to build nests on and the presence of non-native mammalian predators. Overall, populations of Red-footed Boobies in Hawai'i appear to be either stable or increasing due to the fact that most colonies are within official protected areas.
In Kaua'i, Red-footed Boobies are easy to see at almost any coastal location, where they are often seen streaming by just offshore, but often slightly farther out than Brown Boobies. Overall, Red-footed Boobies are a more pelagic species than Brown Booby. The colony of Red-footed Boobies at Kilauea Point NWR is ubiquitous, present year round, and always numbers at least a couple hundred birds. The colonies on O'ahu at Mokapu Peninsula and Moku'manu Islet are readily seen as well, and the species can be seen in small numbers on the other Southeastern Hawaiian Islands. Red-footed Boobies are often associated with flocks of birds following schools of tuna and other predatory fishes, and are thus important to local fishermen for locating fishing grounds.
Dark and light morph adult Red-footed Boobies, Tern Island (Photo by Alex Wang)
The worldwide plumage variation of Red-footed Booby is nothing short of bewildering. In Hawai'i, the species occurs in both brown and white morphs, although the white morph far outnumbers the brown morph. To add to the confusion, the juveniles of both morphs are also brown in coloration. Adult white morph Red-footed Boobies are distinctive (see photo above), being the most common nearly all-white seabird in Hawai'i. The flight feathers are black, but note the all-white tail and smaller size to separate it from the uncommon Masked Booby, which is easy to see only on O'ahu. Adult brown morph Red-footed Boobies usually number only about 1% of the total population in Hawaii, but are distinctive in that they are entirely medium/pale brown with a bright white tail, which separates it from Brown Booby. Juvenile Red-footed Boobies can be difficult to separate from young Brown Boobies, but note the smaller size, thinner wings, and paler brown body plumage of Red-footed Booby (see photo below). In adults, the namesake red feet are always diagnostic, but difficult to see in flight.
Red-footed Booby juvenile, Lehua Islet (Photo by Andre F. Raine)