The Seabirds of the Galápagos

Brian Snyder
College of Life Science, Biology Major
July 4, 2000

Contents:

There are many features that make the Galápagos Islands unique and wondrous and the number and variety of seabirds is definitely one such feature. There are four orders of seabirds in the world, and amazingly, the Galápagos Islands have representatives of all of them. At least seventeen species of seabirds (not counting shorebirds) make their homes in the Galápagos Archipelago surviving off the incredible number of fish living in the waters around the islands. Furthermore, a sizable fraction of these species are found nowhere else in the world, and most of them could be observed from only a few feet away. All of these factors added up to make the Galápagos a truly remarkable place to observe sea birds in the wild.

Seabirds are interesting animals that have had to face many unique challenges in order to evolve into their niches. Certainly one of the biggest of these challenges was the ability to deal with the excess salt that seabirds inevitably ingest. To deal with this problem, seabirds have evolved special glands in their skull which excrete highly concentrated solutions of salt. Also, as an aid to swimming, all seabirds have evolved webbed feet. Although webbing can be greatly beneficial, webbed feet can cause problems, especially for grabbing and perching, thus, seabirds have had to find a balance between the needs and costs of webbing. Finally, although seabirds spend much of their time in the air and the water, they are totally dependent on land for reproduction. Because of this, seabirds must be able to walk. However, many species are extremely awkward on land making them easy targets for terrestrial predators and causing many species to find nesting sites on off-shore, predator-free islands, such as the Galápagos.

The Pelecaniformes Order
The order Pelecaniformes includes many of the seabirds found in the Galápagos. Tropic-birds, pelicans, boobies, cormorants and frigate birds are all members of this group, comprised of about fifty species. Pelecaniformes can be distinguished by their toes, all four of which are webbed and point forward. Also, the chicks of this order are, for the most part, hatched naked and are thus extremely dependent on their parents. Additionally, the nostrils of these birds are often sealed or otherwise protected as an adaptation for diving, a common means of hunting in this order.

The Booby Family
The family Sulidae includes nine species in all, three of which are gannets and six of which are boobies. Three of these six boobies, the red-footed, blue-footed and masked boobies, are found extensively in the Galápagos, however none of them are endemic. Due in part to their forward pointing eyes and interesting sexual displays, boobies are often thought of as somewhat comical looking birds, a stigma which has resulted in their being named after the Spanish word for stupid or clown, bobo. Although they may seem funny looking, boobies are extremely well adapted to their enviornment, and all three of the boobies on the Galápagos are incredible plunge divers. Starting from about five to fifteen or even twenty meters above the water's surface, boobies fold their wings and accelerate straight down towards the ocean, hitting the water at speeds in excess of 10 meters per second (about 23 miles per hour). Just before they hit the water, a third translucent eyelid, the nictitating membrane, covers the eye to protect it from damage. After entering the water, boobies continue to lunge deep into the water. When the reach the end of their dive, sometimes after they have gone fifteen meters underwater, they turn around to return to the surface, trying to catch a fish on their way back up. Boobies, like many seabirds, are colonial birds, nesting together in sometimes very dense groups. In fact, as we hiked around the Islands a couple of times we walked directly through crowded masked booby nesting sites where we were constantly surrounded by booby nests only a few feet away.

Interestingly, although the three species of boobies in the Galápagos are extremely closely related and often inhabit the same islands and geographic areas, they do not compete for resources. They have divided up their niches so that they do not overlap and thus all three species can coexist on the islands without one being driven off the Islands. A good example of this division can be seen in the separation of fishing areas among the boobies. The blue footed boobies, for instance, are primarily inshore feeders while the red footed boobies feed many kilometers out to sea, with the masked boobies somewhere in between.

The Masked Booby
Although not the most populous of the Sulidae species in the Islands, the masked booby (Sula dactylatra) was by far the most commonly seen booby on our trip. While it is the largest of the three boobies in the Islands the size difference between it and its smaller cousins is very difficult to distinguish with the naked eye. Masked boobies are a beautiful white bird with almost no apparent physical difference between the sexes. Their name comes from the dark area surrounding their eyes which gives them a masked appearance. The reproduction of masked boobies is particularly interesting. Their 'nest' consists only of a ring of guano laid on the lava rocks, yet as a part of their courtship ritual, perhaps a leftover from a time when they still built true nests, the male brining the female a twig or stick for their now nonexistent nest. In this 'nest' two eggs are laid, typically about five days apart. After 40 days the first chick hatches, followed a few days later by the second chick. If the first chick is healthy, it will push its younger sibling out of the guano ring at which time it is abandoned and usually devoured by mockingbirds. If, however, the first chick doesn't hatch the second chick grows to reach maturity, fulfilling its role as an insurance policy. Interestingly, the murder of the younger chick by its older sibling will occur regardless of the conditions that year, thus, even in good years when food is plentiful masked boobies will only raise one chick.

The Red-footed Booby
The red-footed booby (Sula sula) is not only the smallest of the boobies in the Galápagos, but it is also the smallest bird in the Sulidae family. It is however, the most populous of the boobies in the Archipelago with 140,000 pairs of birds on the Island of Genovesa alone. Red-footed boobies are able to feed far off shore, sometimes over one hundred kilometers (about sixty miles) out to sea, and are active primarily at night. Perhaps due in part to these incredible distances traveled daily, red-footed boobies are only able to raise one chick at a time, yet unlike their masked relatives, the red-foots only lay one egg and there is, therefore, no need for siblicide. The incubation period of this single egg is forty-five days, and the chicks fledge after an additional 130 days, however, the parents continue feeding the young for some time after fledging. Interestingly, although red-foots, like all Pelecaniformes, have webbed feet, they are able to grip tree branches and can thus nest off the ground in true nests.

The Blue-footed Booby
Possibly the most famous booby in the Galápagos is the blue-footed booby (Sula nebouxxi). While the blue-foots are the least numerous of the three booby species on the Islands, they are by no means endangered and they were very commonly seen on our trip. Although all three boobies have elaborate and similar courtship rituals, the blue-foots have become most famous for theirs which, along with other movements, involves a process known as high-stepping in which the boobies show off their bright blue feet to potential mates, and culminates in a process called sky-pointing in which the boobies point their beaks, wingtips, and tail feathers towards the sky. The blue-footed boobies feed very close to shore, and as a result, they often dive into very shallow water, sometimes less than a meter (3 feet) deep. In fact, while I was snorkeling off a beach one day in water that was only about four or five feet deep, a blue-footed booby plunged into the surf, only a few feet away from my head. Possibly ensuing from their short commute to inshore feeding areas, blue-footed boobies are able to raise more than one chick at a time and can raise three if conditions are favorable.

The Brown Pelican
Also in the order Pelecaniformes is the family Pelecanidae, which contains only one genus, Pelecanus. Within this genus is the brown pelican (Pelecanus occidentalis), the only member of its family in the Galápagos. The brown pelicanis not endemic to the Galápagos and in fact can be found all over the coasts of the United States. In the Galápagos, however, brown pelicans were almost ubiquitous. While the smallest member of its family, the brown pelican is still a rather large bird. The brown pelican, and its Chilean or Peruvian subspecies, are the only truly marine members of their family, and are also the only ones to plunge dive. Although they can dive from ten or fifteen meters (about 35 to 50 feet) above the water's surface, the brown pelicans we saw typically soared only a few meters off the water, then twisted in the air, folded their wings, and fell somewhat comically, towards the water. Once underwater the brown pelican's pouch extends to trap up to 13 liters of water, and with it some fish. The pelicans the bob back to the surface and let the water drain out as they swallow their prey. The pelicans only eat the large fish however, while the smaller ones fall out of the sides of their beaks. Brown noddy terns take advantage of this and perch on pelican's heads waiting to snatch up the small, discarded fish.

Frigate-birds
A third family within the order Pelecaniformes is that of the frigate-birds. In the world there are five species of frigate birds, of the five, two are found in the Galápagos, however, neither is endemic. The two species, the great frigate-bird (Fregata minor) and the magnificent frigate-bird (Fregata magnificens), are extremely similar, both morphologically and ecologically. Both species have extremely high wingspan to bodyweight ratios allowing them soar and to fly extremely well and with excellent control. Using this control, frigate-birds routinely steal food from other birds by grabbing them by their tail feathers and shaking them until they regurgitate their food. Frigate-birds are also capable of capturing their own prey however. Since they have only a small oil gland and very little waterproofing in their wings though, frigate-birds cannot dive and must instead rely on their superb aerobatics to snatch flying fish out of the air.

On our trip we were lucky enough to come during the frigate bird mating season on the island of Genovesa. To attract females, male frigates will blow up their bright red throat pouch and skwalk loudly as females pass overhead. The females will then choose a suitable male and land next to him. The male responds by spreading his huge wings around the female to protect her from other males. A single egg is then laid, and although it can fly after about five months, it stays with, and is dependent on, its parents for about a year. Because of this long investment in each chick, frigate-birds can only mate once every other year.

The Red-Billed Tropicbird
A fourth family in the order Pelecaniformes is that of the tropicbirds, Phaethontidae. There are three species in the world, one of which, the red-billed tropicbird (Phaethon aethereus), inhabits the Galápagos. Tropicbirds are beautiful, mostly white birds with an extremely long central tail feather used in mating displays. They are mostly solitary birds which, like boobies, plunge dive, primarily at twilight, for squid far out to see. Because of this, and the fact that they nest in crevices in cliffs, they were extremely difficult to closely observe.

Flightless Cormorant
The fifth and final family within the order Pelecaniformes, Phalacrocoracidae, is represented in the Galápagos by the endemic flightless cormorant (Nannopterum harrisi). There are 28 other species of cormorants worldwide, and long ago, one of them came to the Galápagos. Slowly, this original founder cormorant, no longer needing the ability to fly in its new, predator-free habitat, lost its wings as an energy saving adaptation. With only its vestigial wings the cormorant relies on swimming through the water to feed on octopus and eels living in the rocks. Unlike penguins, however, cormorants do not use their wings to 'fly' through the water, but instead tuck their wings in and kick with their webbed feet, only using their wings for balance as they hop from rock to rock. Additionally, flightless cormorants do not produce very much oil to waterproof their feathers, therefore, they must hold out their tiny wings to dry.

In the Galápagos, the flightless cormorants only occur on the large western islands of Isabella and Fernandina. Since this is in fact the only place in the world where these remarkable birds live, the size of their species is frighteningly low at only about 1000 pairs.

Penguins
While it may be surprising to think of penguins at the equator, there is an endemic species of penguin, a member of the Sphenisciformes order, living in the surprisingly cool waters surrounding the Galápagos. A small penguin (about 30 cm), the Galápagos penguin (Spheniscus mendiculus) is the only penguin to live north of the equator as well as the only species totally restricted to the tropics. Although on land the Galápagos penguin is a somewhat awkward and very amusing bird as it waddles and hops along the rocks in the water penguins are excellent swimmers, quickly achieving speeds of up to 35 kilometers per hour (almost 22 mph)

The Tube-Nosed Birds
Distant relatives of the Galápagos penguin, the tube-nosed birds (Procellariiformes) get their name from their long, tubular nostrils and hooked bill. The most marine of the seabirds, many of the tube-nosed birds spend the vast majority of their lives on the sea, only setting foot on land in order to mate.

Waved Albatross
The endemic waved albatross (Diomedea irrorata) is by far the most notable and majestic representative of the tube-nosed order in the Galápagos. They are huge birds which spend most of their lives sitting on the waves off the coast of Peru and only come to land to land to mate, an event which, for the most part, only takes place on the Island of Española in the Galápagos. Although the albatross is an excellent flier, its abilities at taking-off are somewhat limited, thus in order to fly, the waved albatross must toddle its way to the cliffs of Española and literally fall off the edge, spreading its enormous wings as it does so. During courtship, an event which we were lucky enough to see, waved albatrosses perform an elaborate and noisy mating ritual which involves the pair knocking their bills together, shifting their necks from side to side, pointing their beaks into the air and a number of other movements. Like many seabirds, the waved albatross has an extremely long lifespan, often over 40 years, yet amazingly, they remain monogamous throughout their lives.

Storm Petrels
While the waved albatross may be the largest seabird in the Galápagos, one of its close relatives, the storm petrel, is the world's smallest seabird. About the size of an average North American perching bird (15-20 cm), storm petrels hover just above the water while patting the surface of the water with their feet to stir up food. There are three very similar species of storm petrels in the Galápagos the band-rumped (Oceanodroma castro), the white-vented (Oceanites gracilis), and the Galápagos (Oceanodrama tethys) storm petrel. All three species are mostly black birds with white patches on their tail feathers.

Hawaiian Petrel
While for the most part, the seabirds of the Galápagos have been spared from man's ecologically destructive nature there are some exceptions. One such exception is the Hawaiian petrel (Pterodroma phaeopygia), the only true petrel in the Galápagos. Another relative of the albatross and a member of the Procellariiformes order, the Hawaiian petrel has been threatened both in the Galápagos and elsewhere by introduced rats which eat the Hawaiian petrel's eggs and chicks.

Order Chadadriiformes
The final order of seabirds is a diverse mix of true seabirds and shore birds know as the Charadriiformes. There are three members of this order in the Galápagos: the brown noddy tern, and the swallow-tailed gull, and the lava gull.

Gulls
Gulls, or sea gulls as they are commonly known, are medium sized seabirds which have adapted remarkably well to their environment. Unlike many of the other seabirds we saw, they walk fairly well, and they are extremely good swimmers and flyers. The 45 species of gulls live on virtually every shoreline in the world, and many species have now modified their lifestyle in order to thrive with man.

The lava gull (Larus fuliginosus) is an endemic, grayish gull with a white ring around its eye. With only about 400 pairs it is thought to be the world's rarest gull. While the lava gull may appear somewhat plain, the swallow-tailed gull is, for a gull, an extravagantly colored bird. Considered endemic, the swallow-tailed gull (Larus furcatus) is the world's only nocturnal gull. At dusk it flies many kilometers out to see to feed on bioluminescent squid, which they can find with their especially large and well adapted eyes. Upon returning to the Islands, the birds produce clicking sounds, which have been hypothesized to be a primitive form of echolocation.

Terns
Another interesting seabird which we encountered in the Galápagos is the brown noddy tern (Anous stolidus). Perhaps the tern's most interesting quality, noddies perch on the heads of brown pelicans attempting to capture any fish that escaped from the bill of a fishing pelican. A number of times while in the Galápagos we saw this unusual behavior. Although by seabird standards, the noddy tern is at best a medium sized bird, it is still a surprisingly large bird to be perching on the head of a pelican. Finally, the sooty tern, a close relative of the noddy tern, also lives in the Galápagos, however, because of its small local population, most visitors, including us, don't see it.

While all of these seabirds are truly incredible, to me the most amazing thing about them was how many of them there were, and how close we could get to them. The seabirds in general, but especially the boobies, pelicans and frigate-birds were practically omnipresent. Every morning, as we arrived at a different island, I would walk onto the deck of our ship and watch a multitude of seabirds diving near the shores. Moreover, it became routine to get within a few feet of the birds without them seeming to care about my presence at all. Overall, going to the Galápagos Islands was an incredible experience and one I can't wait to repeat. Although the seabirds were an outstanding part of the fauna of the Islands, there are a great number of other wondrous species of animals and plants living in the Archipelago, and when all these factors are taken into account it becomes clear how remarkable and unique the Galapagos are.

Additional Reading

Horwell, David and Oxford, Pete. Galápagos Wildlife, A Visitor's Guide. Bucks, England: Bradt Publications, 1999.
Lofgren, Lars. Ocean Birds. Gothenburg, Sweden: Croom Helm Ltd. 1984.
Lockley, Ronald. Seabirds of the World. New York: Facts on File, Inc. 1984.

Also Visit

The Cornell University Website at http://www.geo.cornell.edu/geology/Galapagos.html
The Charles Darwin Research Station's Website at http://www.darwinfoundation.org
Spacelab.net at http://www.spacelab.net/~cni/indexexp.html