FRIGATEBIRDS Aerial ATTITUDE Text and photographs by Ross Wanless he size of an albatross; the grace patrol the flyways, picking off hapless of a tern; the belligerence of a victims as they return for the night. Once skua; the speed of a swift; the they have selected a victim, as many as agility of a flycatcher and the five to 10 frigatebirds will give chase. Tattitude of... well, a frigatebird. These They pull on the victim’s tail feathers, amazing seabirds are the undisputed, if bite its legs, drag it by a wing-tip and even somewhat despotic kings of the world’s stick their bills down the other bird’s gul- tropical oceans. let to grab fish. Birds that choose to resist Frigatebirds are impressive creatures by can suffer lethal consequences, such as whatever yardstick one chooses to meas- broken wings or becoming completely ure them. They are highly specialised exhausted. Often the victim will regurgi- seabirds, completely in tune with their tate some of its crop contents, and the environment. So well adapted, in fact, frigatebirds will then dive and chase the that they have pared down to the abso- ill-gotten gains. But they must catch it lute minimum anything not essential to before it hits the water and sinks, for their mode of living. Those features that ironically frigatebirds, despite being sea- are essential they have souped up to the birds, have no waterproofing. If they land extremes that drag-racing enthusiasts in the sea, they drown. would appreciate. For a seabird not to have waterproof Their fame is widespread, well deserved, feathers sounds absurd, but frigatebirds and comes for several reasons. Perhaps have achieved this. It is questionable the most obvious trait is their well-known whether or not the ancestors of frigate- habit of attacking other seabirds, which birds ever had waterproofing, but it seems they do ostensibly to get a free lunch. probable that they did. Somewhere along Basically, they are the biggest and mean- their evolutionary path they became so Opposite Frigatebirds live hard and est kids on the block: they pick on other proficient at catching food in mid-air that play hard, are powerful and aggressive birds, bullying and harassing them until they did away with their waterproofing. predators, yet so light and manoeuvrable they cough up lunch money. Seabirds It is a popular myth that frigatebirds are that they can pick a twig off the surface returning to roost generally have a full obligate klepto-parasites (in other words, of the ocean. crop of fish and frigatebirds are wont to that they derive a living from pirating 36 FRIGATEBIRDS AFRICA – BIRDS & BIRDING 1 1 2 2 3 3 4 other seabirds’ food). This is probably just as important is to be skilled metres. But size is not everything: they half a frigatebird’s weight. Frigatebirds are 4 5 clearly not the case: if noth- at pilfering nesting material. Another of also have the lowest wingloading of any by far the biggest birds that can hover 5 6 ing else, simple mathematics the frigatebird’s extreme adaptations is bird. For birds the size of frigatebirds to without a headwind. They can also fly 6 7 tells us so. For example, on the reduction of its feet and legs to such a achieve that is truly astronomical engi- more slowly than just about any other 7 8 Aldabra Atoll in the Indian degree that they can only be used for neering. Wingloading is the ratio between bird without falling out of the sky. With a 8 9 Ocean there are approximate- perching (and then only just). The birds the weight of a bird and the surface area reasonable breeze, they can even achieve 9 10 ly 10 000 frigatebirds (the cannot walk on land and thus struggle to of its wings. Clearly, the heavier a bird is, take-off without flapping – they simply 10 11 second largest colony in the find material with which to construct the bigger the surface area needed to spread their wings and float away. 11 12 world), and a similar number their nests. Dispossessing other frigate- achieve lift. Small birds such as sunbirds Yet another feature that makes frigate- 12 13 of Red-footed Boobies. It is birds and boobies of their twigs, especially have very low wingloading ratios, and birds so adept at aerobatics is the shape of 13 14 in conceivable that the boo- in the air before the birds can access the consequently are highly manoeuvrable. their wings. Straight, level wings are good 14 15 bies could find enough food relative safety of a nest, is a very valuable Bigger birds, like ducks and geese, have surfaces for gliding; angular, curved wings 15 16 to support both themselves skill for breeding birds. Getting free fish is such high wingloading ratios that they are good for agility. Albatrosses are 16 17 and the frigatebirds. probably an added bonus during training often have to run on the water before tak- extreme examples in the straight-winged 17 18 Frigatebirds eat flying fish sessions. However, having watch ed their ing off, and must flap really fast to stay in department, as they have little need for 18 19 and flying squid almost evening antics for many hours, I firmly- the air. There is a fairly neat trend in birds: tight cornering or rapid changes in direc- 19 20 exclusively, hawking them believe that frigatebirds simply have ‘atti- the bigger they are, the higher their win- tion. Most birds lie somewhere along the 20 21 out of the air or from just tude’, and that they enjoy beating up gloading. spectrum, with more bowed shapes occur- 21 22 below the water’s surface as smaller birds. One of the ways frigatebirds achieve ring in birds that need more twisting and 22 23 When a male frigatebird is not display- the flying fish flee predators So what is it that makes the frigatebirds their low wingloading is having hollow turning power. Predictably, frigatebirds 23 24 ing, his gular pouch is visible only as a from below, principally tunas and dol- so good at overhauling other seabirds and (pneumatised) bones which, all told, con- have highly bowed wings, making them 24 25 relatively small flap of skin on his throat. phins. Chasing down birds is perfect looting their lunch? For a start, they have tribute less than five per cent to the birds’ look the part of a child’s depiction of sea- 25 26 practice for the a massive wingspan – a Greater Frigate- weight. In fact, the feathers and flight birds in the distance – gently-sloping ‘M’s. 26 27 aerial manoeuvring needed to capture bird’s wings stretch to more than two muscles (arguably the two most critical Their wings are also more bent at the 27 28 the much less agile flying fish. But it is metres, Magnificent Frigatebird’s to 2.5 features for flight) combined account for wrist than other birds’, further improv- 28 29 29 30 30 31 31 32 32 33 islands throughout 33 34 Relatively speaking... tropical oceans. 34 35 rigatebirds have the remnants of webs Off Africa, both the Ascension and a few Magnificent frigatebirds 35 36 F joining all four toes on their somewhat occur off the west coast, whereas Greater and Lesser frigatebirds 36 37 atrophied feet. This single character has been occur off the east coast, with vagrants reaching the southern tip of 37 38 used to place them along with pelicans, cor- the continent. There have been claims of Christmas Frigatebirds from 38 39 morants, gannets and boobies in the order the Kenya coast, but these remain unsubstantiated. Given their great 39 40 Pelecaniformes. However, recent molecular powers of flight, vagrancy is fairly common. However, the correct iden- 40 41 evidence strongly suggests that this classifica- tification of single, out-of-range birds requires careful observation. 41 42 tion is incorrect, and that frigatebirds are 42 43 more closely related to albatrosses, petrels, 43 44 divers and penguins. 44 45 Worldwide there are five species of frigate- 45 46 birds in a single genus, Fregata: 46 47 Ascension Frigatebird F. aquila Breeds only 47 48 on Boatswainbird Island off Ascension Island, 48 49 central Atlantic Ocean. Conservation status: The atrophied feet, showing the vestiges of webbing 49 50 Vulnerable between the toes, are shown clearly in this female 50 51 Christmas Frigatebird F. andrewsi Breeds Greater Frigatebird. 51 52 only on Christmas Island, an Australian island 52 53 south-east of Sumatra. Conservation status: Frigatebirds are unusual among seabirds in being sexually dimor- 53 54 Critically Endangered phic, with males being mostly or entirely black, and females having 54 55 Magnificent Frigatebird F. magnificens varying amounts of white on the breast or belly. Differences between 55 56 Breeds on tropical islands off the Americas, the species are rather subtle, especially among adult males. Their 56 57 with a very small population, relict on the identification is further complicated by each species having a series of 57 58 PETER RYAN (3) Cape Verde Islands, off West Africa juvenile and immature plumages. Young birds typically have pale 58 59 Puff daddy... a Magnificent Frigatebird in breeding condition displays his Greater Frigatebird F. minor Breeds widely heads and breasts, and take several years to acquire adult plumage. 59 60 inflated gular pouch. on islands throughout tropical oceans An immature Magnificent Frigatebird. PETER RYAN 60 61 Lesser Frigatebird F. ariel Breeds widely on 61 62 62 38 FRIGATEBIRDS AFRICA – BIRDS & BIRDING FEBRUARY/MARCH 2002 FRIGATEBIRDS 39 1 2 3 ing their agility.