Blue-footed Boobies, Sula nebouxii
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Description & Behavior
Blue-footed boobies, Sula nebouxii (Milne-Edwards, 1882), are famous for two reasons: their link to Charles Darwin's expedition to the Galapagos Islands, and their name. The appellation does in fact have a somewhat silly meaning: The word "booby" comes from the Spanish "bobo," meaning "stupid fellow," and was probably inspired by the bird's clumsiness on land and apparently unwarranted bravery. (They are extremely vulnerable to human visitors because they do not appear to fear us.) A tropical seabird with famous bright blue webbed feet, a brown and white-streaked head, blue-gray facial skin, and a solid white body, they may approach 1.5 m in wingspan. The bird itself is a little under a meter long (about the size of a goose), with a long curved neck and can live as long as 17 years.
World Range & Habitat
Though best-known as a Galapagos inhabitant, blue-footed boobies can be found on several other arid islands off the western coasts of tropical America, Mexico, and northern South America, from the coast of California to southern Peru.
Feeding Behavior (Ecology)
A skilled hunter in the air and on water despite its awkward gait on land, blue-footed boobies dine solely on fish. Flying over the water, generally no higher than 25 m, they keep their bill pointed downward, poised for action. When they spot a fish they break into a graceful dive, making almost no splash as they enter the water like an arrow, then popping up on the surface a few feet away with their prize. These birds are such accurate dive bombers that they have even been known to catch flying fish mid-leap. Unlike other boobies, blue-footed boobies can also dive from a floating position on the surface of the water as well.
Blue-footed boobies prefer to eat alone, but they are not entirely opposed to group dining and occasionally hunts cooperatively in flocks. When a member of the flock spots a fish, they will whistle to alert the others, and the entire flock descends, perfectly synchronized, on its unlucky prey. Males are smaller, and thus tend to stick with shallow dives closer to shore, while heavier females make deeper dives offshore.
Even if the name doesn't make you laugh, a blue-footed booby's elaborate courtship rituals might. Breeding may occur at any time of year. First the male flaunts his brilliant blue feet with an exaggerated high-stepping strut. Then he presents nest materials to the female. A brief courtship flight follows, after which the male proudly flashes his blue feet to the female once more. Then, both male and female tilt their bills upward, giving respectively a piercing whistle and a series of groans. Mating follows.
Female blue-footed boobies usually lay two or three blue-green eggs in shallow depressions on flat ground, far away from other nests. The blue-footed booby lacks "brooding patches" of skin to keep the eggs warm, so instead it uses its feet to incubate them. (Despite their blue appearance, the feet have an excellent blood supply.) The eggs take about 45 days to hatch, after which time the female will balance them on top of her feet for a month. Both parents feed the chicks continuously with regurgitated fish through their bills. In the event of a famine, the parents will feed only the largest chick, sacrificing the others. Chicks stay with their parents for about two months.
Conservation Status & Comments
Blue-footed boobies are legally protected on the Galapagos Islands, where breeding pairs number under 20,000. The other populations around the world (numbering about 20,000 total) are slightly threatened by egg collectors.
References & Further Research
Research Sula nebouxii » Barcode of Life ~ BioOne ~ Biodiversity Heritage Library ~ CITES ~ Cornell Macaulay Library [audio / video] ~ Encyclopedia of Life (EOL) ~ ESA Online Journals ~ FishBase ~ Florida Museum of Natural History Ichthyology Department ~ GBIF ~ Google Scholar ~ ITIS ~ IUCN RedList (Threatened Status) ~ Marine Species Identification Portal ~ NCBI (PubMed, GenBank, etc.) ~ Ocean Biogeographic Information System ~ PLOS ~ SIRIS ~ Tree of Life Web Project ~ UNEP-WCMC Species Database ~ WoRMS
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