By: Eva Gruber
Continuing our series on seabirds of this blue planet, we come to the fourth avian order containing seabirds.
Suliformes
Over the past two decades taxonomy of animals has come under intense study with the move from physical to genetic relationships. Suliformes is a relatively new order. The families in Suliformes were once all classified under Pelicaniformes as birds with totipalmate feet (four toes connected with webbing). However, with molecular study it became evident that several of the families were actually not all that closely related to the pelicans, and were therefore extracted and given their own order.
The Sulidae family is comprised of ten species of boobies and gannets. Sulids are plunge-diving seabirds that remain mostly coastal, not venturing in the open pelagic like albatross and shearwaters.
They all share a similar body form with long tapered wings, short, stout legs, with a long, lozenge-shaped tail with shorter outer retrices (tail feathers) and longer inner retrices. Their breast muscles are, by necessity, rather small which allows them to plunge-dive for prey with greater streamlining. The cost of this is that their wing-loading is rather high, making flying a strenuous activity.
Sulids also have unique nostrils that open into the bill rather than the outside – this is another adaptation for plunge-diving, preventing water from being forced in.
Credit Image: © National News/ZUMAPRESS.com
The eyes of Sulids face forward, allowing them binocular vision. This makes them more efficient predators, better able to judge distances. This feature also giving them a distinctly goofy look beak-on.
The name “booby” perhaps comes from this goofy look, or perhaps from the Spanish word bobo which means “stupid” – as the birds have a habit of landing on ships to rest which, unfortunately, made them very easy to catch and eat by conquistadors.
In some species, the totipalmate (all four toes connected by webbing) feet are brightly colored during the breeding season and are used in courtship displays. The most famous example of this is the Blue-footed Booby.
Both males and females have blue feet, but the males display them with great pride in order to show off to females. Females will choose a mate based on the brightness of their feet. While they are not conscious of the reason they are drawn to bright feet, it has been shown that younger and fitter males have the brightest feet. For this reason it has been concluded that brightness is a sign of high reproductive and genetic quality. Females also provide more care to their young if their mate has bright feet. Females that mate with brighter-footed males lay larger eggs and fledge more young.
Boobies lay two eggs, a few days apart. The chick that hatches first is larger and usually will kill its younger sibling in years where food is not abundant throughout the entire season. This is called facultative siblicide, where the second chick is a sort of insurance in case the first chick dies. However, the parents usually cannot provide enough food for both chicks unless it is a super-productive year for where there is an abundance of prey. While this behavior seems exceptionally cruel, it evolved because it was advantageous in the propagation of sulid genes in their specific environmental conditions. Examples like this remind us that as beautiful as these birds are, nature truly is “red in tooth and claw.”
There are three species of gannet: the Northern (found in the Atlantic), the Australasian (found in South Pacific), and the Cape Gannet (found around the African Cape). The gannet is very similar to boobies in shape.
One extraordinary instance of dispersal due to climate change is the presence of a single Northern Gannet on the Farallon Islands off the coast of California, pictured below. I took this picture of him attending a colony of Brandt’s Cormorants during the summer breeding season. This bird is the only Northern Gannet in the entire Pacific Ocean.
This bird is thought to have migrated across the Northwest Passage in the Arctic which, normally covered in sea ice, has in recent years experienced too high temperatures to form sea ice. This is due to climate change and warming ocean conditions which are especially pronounced at the poles. 2016 is the fourth year that the gannet has resided at the Farallones after surviving his extraordinary journey of thousands of miles. He is able to plunge-dive for fish in the Pacific just as well in the Atlantic, although during the breeding season he gets restless searching for a mate.
Also within the Sulid family are Fregatidae, or frigatebirds. These birds are found across all tropical and subtropical oceans. The males and females are sexually dimorphic. The males have enormous bright red gular (throat) pouches which they inflate and use in their courtship displays.
Frigatebirds spend most of their day searching for food. They often resort to kleptoparasitism, meaning that they will steal food from other birds. They are literally pirate birds, pulling at feathers and dive-bombing in the air until the victim releases or throws up its fish. If this does not provide them with enough food, they will also plunge-dive for fish and squid.
Phalocroracidae
This family consists of cormorants and shags. There are 40 species found around the world, although the exact taxonomy of this group is rather up in the air for now. Most species have dark feathers that are not waterproofed, meaning that after swimming in the water, their feathers must be dried out. Cormorants can often be seen on land spread-winged, as they try to use the sun and wind to dry their waterlogged feathers.
Cormorant bills are long and hooked, and excellent for grasping fish. They are pursuit-divers, using their large feet to propel themselves under the surface as try to catch prey. Cormorants and shags are coastal rather than oceanic seabirds, sticking to nearshore waters and breeding on islands and the coast. There is a uniquely flightless species of cormorant on the Galapagos.
Cormorants have a long and storied history with humans – from being maligned (and called the “devilbird”), despised, and exterminated by fishermen from Mississippi to Malaysia as competitors for fish, to being used as domesticated fish-fetching “tools” in Asia. Peruvians long mined their guano for fertilizer, enabling them to eke out an existence as farmers in an otherwise harsh environment. In John Milton’s book Paradise Lost, cormorants are demonized as Satan takes the form of a cormorant to spy on Adam and Eve. The cormorant is perhaps the world’s most misunderstood and under appreciated waterbird.
Sulids are a wonderfully diverse family of beautiful seabirds, and personally remain one of my favorite groups.