The

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Sulidae comprises the

gannet Gannets are seabirds comprising the genus ''Morus'' in the family Sulidae, closely related to boobies. Gannets are large white birds with yellowish heads; black-tipped wings; and long bills. Northern gannets are the largest seabirds in the ...

s and

boobies A booby is a seabird in the genus ''Sula'', part of the family Sulidae. Boobies are closely related to the gannets (''Morus''), which were formerly included in ''Sula''. Systematics and evolution The genus ''Sula'' was introduced by the Fren ...

. Collectively called sulids, they are medium-large coastal

seabird Seabirds (also known as marine birds) are birds that are adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same enviro ...

s that plunge-dive for

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of ...

and similar

prey Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill ...

. The 10

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

in this family are often considered congeneric in older sources, placing all in the

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

''Sula''. However, ''Sula'' (true boobies) and ''Morus'' (gannets) can be readily distinguished by morphological,

behavioral Behavior (American English) or behaviour (British English) is the range of actions and mannerisms made by individuals, organisms, systems or artificial entities in some environment. These systems can include other systems or organisms as we ...

, and DNA sequence characters.

Abbott's booby Abbott's booby (''Papasula abbotti'') is an endangered seabird of the sulid family, which includes gannets and boobies. It is a large booby and is placed within its own monotypic genus. It was first identified from a specimen collected by Will ...

(''Papasula'') is given its own genus, as it stands apart from both in these respects. It appears to be a distinct and ancient lineage, maybe closer to the gannets than to the true boobies.Kennedy, Martyn; Spencer, Hamish G. & Gray, Russell D. (1996): Hop, step and gape: do the social displays of the Pelecaniformes reflect phylogeny? ''Animal Behaviour'' 51(2): 273-291. (HTML abstract) Erratum: ''Animal Behaviour'' 51(5): 1197.

Description

Sulids measure about in length and have a wingspan around . They have long, narrow, and pointed wings, and a quite long, graduated, and rather lozenge-shaped tail whose outer feathers are shorter than the central ones. Their flight muscles are rather small to allow for the small cross-section required for plunge-diving, as an adaptive trade-off relative to some sacrifice in flight performance. Consequently, they are very

streamlined Streamlines, streaklines and pathlines are field lines in a fluid flow. They differ only when the flow changes with time, that is, when the flow is not steady. Considering a velocity vector field in three-dimensional space in the framework of ...

, reducing drag, so their bodies are "

torpedo A modern torpedo is an underwater ranged weapon launched above or below the water surface, self-propelled towards a target, and with an explosive warhead designed to detonate either on contact with or in proximity to the target. Historically, s ...

-shaped" and somewhat flat.Nelson, J. Bryan (2003): Gannets and Boobies. ''In:'' Perrins, C. (ed.): ''The Firefly Encyclopedia of Birds'': 82–87. Firefly Books, Oxford. They have stout legs and

webbed feet The webbed foot is a specialized limb with interdigital membranes (webbings) that aids in aquatic locomotion, present in a variety of tetrapod vertebrates. This adaptation is primarily found in semiaquatic species, and has convergently evolved m ...

, with the web connecting all four toes. In some species, the webs are brightly colored and used in

courtship display A courtship display is a set of display behaviors in which an animal, usually a male, attempts to attract a mate; the mate exercises choice, so sexual selection acts on the display. These behaviors often include ritualized movement ("dances"), ...

s. The bill is usually conspicuously colored, long, deep at the base, and pointed, with saw-like edges. The upper mandible curves down slightly at the tip and can be moved upward to accept large prey. To keep water out during plunges, the nostrils enter into the bill rather than opening to the outside directly. The eyes are angled forward, and provide a wider field of

binocular vision In biology, binocular vision is a type of vision in which an animal has two eyes capable of facing the same direction to perceive a single three-dimensional image of its surroundings. Binocular vision does not typically refer to vision where an ...

than in most other birds. Their plumage is either all-white (or light brownish or greyish) with dark wingtips and (usually) tail, or at least some dark brown or black above with white underparts; gannets have a yellowish hue to their heads. The face usually has some sort of black markings, typically on the lores. Unlike their relatives (the

darter The darters, anhingas, or snakebirds are mainly tropical waterbirds in the family Anhingidae, which contains a single genus, ''Anhinga''. There are four living species, three of which are very common and widespread while the fourth is rarer and ...

s and cormorants), sulids have a well-developed preen gland whose waxy secretions they spread on their feathers for waterproofing and pest control. They

moult In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is the manner in which an animal routinely casts off a part of its body (often, but not always, an outer ...

their tail feathers irregularly and the flight feathers of their wings in stages, so that starting at the first moult, they always have some old feathers, some new ones, and some partly grown ones. Moult as a response to periods of

stress Stress may refer to: Science and medicine * Stress (biology), an organism's response to a stressor such as an environmental condition * Stress (linguistics), relative emphasis or prominence given to a syllable in a word, or to a word in a phrase ...

has been recorded.

Distribution and ecology

The sulids are distributed mainly in

tropical The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also referred to ...

and subtropical waters, but they, particularly gannets, are found in

temperate In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout ...

regions, too. These birds are not truly

pelagic The pelagic zone consists of the water column of the open ocean, and can be further divided into regions by depth (as illustrated on the right). The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or w ...

seabirds like the related

Procellariiformes Procellariiformes is an order (biology), order of seabirds that comprises four family (biology), families: the albatrosses, the Procellariidae, petrels and shearwaters, and two families of storm petrels. Formerly called Tubinares and still call ...

, and usually stay rather close to the coasts, but the abundant colonies of sulids that exist on many

Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the contine ...

islands suggest that they are not infrequently blown away from their home range by

storm A storm is any disturbed state of the natural environment or the atmosphere of an astronomical body. It may be marked by significant disruptions to normal conditions such as strong wind, tornadoes, hail, thunder and lightning (a thunderstorm), ...

s, and can wander for long distances in search of a safe place to land if need be. All

feed entirely at sea, mostly on mid-sized

and similarly sized marine

invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...

s (e.g. cephalopods). Many species feed communally, and some species follow

fishing boat A fishing vessel is a boat or ship used to catch fish in the sea, or on a lake or river. Many different kinds of vessels are used in commercial, artisanal and recreational fishing. The total number of fishing vessels in the world in 2016 was ...

s to

scavenge Scavengers are animals that consume dead organisms that have died from causes other than predation or have been killed by other predators. While scavenging generally refers to carnivores feeding on carrion, it is also a herbivorous feeding b ...

discarded bycatch and chum. The typical hunting behavior is a dive from midair, taking the bird a 1–2 m under water. If prey manages to escape the diving birds at first, they may give chase using their legs and wings for underwater swimming. As noted above, the

traits of gannets and boobies differ considerably, but the Sulidae as a whole are characterized by several behavioral synapomorphies: Before taking off, they point their bills upwards (gannets) or forward (boobies). After landing again, they point downwards with their bills. In response to a threat, they do not attack, but shake their heads and point their bills towards the intruders.

Reproduction

All sulids breed in

colonies In modern parlance, a colony is a territory subject to a form of foreign rule. Though dominated by the foreign colonizers, colonies remain separate from the administration of the original country of the colonizers, the '' metropolitan state'' ...

. Males examine the colony area in flight and then pick a nest site, which they defend by fighting and territorial displays. Males then advertise to females by a special display and call. Their display behavior is characteristic, though not as diverse as the numerous variations found among the cormorants; it typically includes the male shaking his head. Females search the colony in flight and on foot for a mate. Once they select males, pairs maintain their bonds by preening each other and by frequent copulation. Abbott's booby fledgling

The clutch is typically two

eggs Humans and human ancestors have scavenged and eaten animal eggs for millions of years. Humans in Southeast Asia had domesticated chickens and harvested their eggs for food by 1,500 BCE. The most widely consumed eggs are those of fowl, especial ...

. The eggs are unmarked (but may become stained by

debris Debris (, ) is rubble, wreckage, ruins, litter and discarded garbage/refuse/trash, scattered remains of something destroyed, or, as in geology, large rock fragments left by a melting glacier, etc. Depending on context, ''debris'' can refer to ...

in the nest), whitish, pale blue, green, or pink, and have a coating that resembles

lime Lime commonly refers to: * Lime (fruit), a green citrus fruit * Lime (material), inorganic materials containing calcium, usually calcium oxide or calcium hydroxide * Lime (color), a color between yellow and green Lime may also refer to: Botany ...

. Egg weight ranges from 3.3 to 8.0% of the female's weight. Incubation lasts 42 to 55 days, depending on the species. Both sexes incubate; like their relatives, they do not have brood patches, but their feet become

vascular The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away f ...

ized and hot, and the birds place the eggs under the webs. Eggs lost during the first half of incubation are replaced. At hatching, parents move the eggs and then the hatchlings to the tops of their webs. The young hatch naked, but soon develop white down. They beg by touching the parent's bill and take regurgitated food straight from its

gape The beak, bill, or rostrum is an external anatomical structure found mostly in birds, but also in turtles, non-avian dinosaurs and a few mammals. A beak is used for eating, preening, manipulating objects, killing prey, fighting, probing for food ...

. At first, at least one parent is always in attendance of the

altricial In biology, altricial species are those in which the young are underdeveloped at the time of birth, but with the aid of their parents mature after birth. Precocial species are those in which the young are relatively mature and mobile from the mome ...

young; after two weeks, both parents leave the nest unguarded at times while they go fishing. The times for the chicks to fledge and become independent of their parents depend greatly on the food supply. Rarely does more than one chick survive to maturity, except in the

Peruvian booby The Peruvian booby (''Sula variegata'') is an endemic bird of the Peruvian current, and an important predator of the marine community to which it belongs. Its distribution is much less widespread than other closely related booby species. It is th ...

(''Sula variegata''), which has the biggest clutch (two to four eggs), and less often in the blue-footed booby (''S. nebouxii''). Siblicide by the stronger of two chicks is frequent.

Systematics and evolution

Masillastega rectirostris holotype sp140b

Sulids are related to a number of other aquatic birds, which all lack external

nostril A nostril (or naris , plural ''nares'' ) is either of the two orifices of the nose. They enable the entry and exit of air and other gasses through the nasal cavities. In birds and mammals, they contain branched bones or cartilages called turbi ...

s and a brood patch, but have all four toes webbed and a

gular sac Gular skin (throat skin), in ornithology, is an area of featherless skin on birds that joins the lower mandible of the beak (or ''bill'') to the bird's neck. Other vertebrate taxa may have a comparable anatomical structure that is referred to as e ...

. The closest living relatives of the Sulidae are the

Phalacrocoracidae Phalacrocoracidae is a family of approximately 40 species of aquatic birds commonly known as cormorants and shags. Several different classifications of the family have been proposed, but in 2021 the IOC adopted a consensus taxonomy of seven gen ...

(cormorants and shags) and the Anhingidae (darters). The latter are somewhat intermediate between sulids and cormorants, but (like many cormorants) they are freshwater birds in a clade containing otherwise

s, and also symplesiomorphic with sulids but synapomorphic with cormorants in some other respects. Thus, the Sulidae seem to be the oldest and most distinct lineage of those three, which are united in a suborder Sulae. Therein, the Sulidae are typically placed simply as a

; sometimes, a superfamily Suloidea is recognized, wherein some of the primitive prehistoric forms (e.g. '' Empheresula'', '' Eostega'', and '' Masillastega'') are placed as basal lineages distinct from the living Sulidae. However, the proposed family Pseudosulidae (or Enkurosulidae) is almost certainly invalid. Olson, Storrs L. (1985): Section X.G.5.a. Sulidae. ''In:'' The Fossil Record of Birds. ''Avian Biology'' 8: 203-204
PDF fulltext
/ref> Christidis, Les & Boles, Walter E. (2008): ''Systematics and Taxonomy of Australian Birds''. CSIRO Publishing, CollingwoodVictoria, Australia.
Excerpt
at

Google Books Google Books (previously known as Google Book Search, Google Print, and by its code-name Project Ocean) is a service from Google Inc. that searches the full text of books and magazines that Google has scanned, converted to text using optical ...

p.100Mayr, Gerald (2009): 7.1.3 Sulidae (Gannets and Boobies). ''In: Paleogene Fossil Birds'': 64-65. Springer-Verlag, Heidelberg & New York.
Excerpt
at

The Sulae were traditionally included in the

Pelecaniformes The Pelecaniformes are an order of medium-sized and large waterbirds found worldwide. As traditionally—but erroneously—defined, they encompass all birds that have feet with all four toes webbed. Hence, they were formerly also known by such n ...

in its obsolete paraphyletic circumscription, but pelicans, the namesake family of the Pelecaniformes, are actually more closely related to herons, ibises and spoonbills, the

hamerkop The hamerkop (''Scopus umbretta'') is a medium-sized wading bird. It is the only living species in the genus ''Scopus'' and the family Scopidae. The species and family was long thought to sit with the Ciconiiformes but is now placed with the ...

, and the

shoebill The shoebill (''Balaeniceps rex'') also known as the whalebill, whale-headed stork or shoe-billed stork, is a very large long-legged wading bird. It derives its name from its enormous shoe-shaped bill. It has a somewhat stork-like overall form ...

than to the sulids and allies. In recognition of this, the Sulae have been proposed for separation in a new order Phalacrocoraciformes, which also includes the

frigatebird Frigatebirds are a family of seabirds called Fregatidae which are found across all tropical and subtropical oceans. The five extant species are classified in a single genus, ''Fregata''. All have predominantly black plumage, long, deeply forked ...

s (Fregatidae), as well as one or more prehistoric lineages that are entirely extinct today. The IOC World Bird List uses Suliformes as the proposed order name. Within the family itself, three living genera—'' Sula'' (boobies, six species), ''

Papasula Abbott's booby (''Papasula abbotti'') is an endangered seabird of the sulid family, which includes gannets and boobies. It is a large booby and is placed within its own monotypic genus. It was first identified from a specimen collected by Willi ...

'' (Abbott's booby), and '' Morus'' (gannets, three species)—are recognized. A 2011 study of multiple genes found Abbott's booby to be basal to all other gannets and boobies, and likely to have diverged from them around 22 million years ago, and the ancestors of the gannets and remaining boobies split around 17 million years ago. The most recent common ancestor of all boobies lived in the late Miocene around 6 million years ago, after which time the boobies steadily diverged. The gannets split more recently, only around 2.5 million years ago. The

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

record of sulids is quite extensive due to the many

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', " ...

, and all things (such as the Early Eocene

'' Limnofregata'') considered, the sulids seem to have diverged from the lineage leading to cormorants and darters around 50 million years ago (Mya), perhaps a bit earlier. The initial

evolutionary radiation An evolutionary radiation is an increase in taxonomic diversity that is caused by elevated rates of speciation, that may or may not be associated with an increase in morphological disparity. Radiations may affect one clade or many, and be rapid ...

formed a number of genera that are now completely extinct, such as the freshwater '' Masillastega'' (which, as noted above, might not have been a modern-type sulid) or the bizarre '' Rhamphastosula'' (which had a bill shaped like an

aracari An aracari or araçari ( , , ) is any of the medium-sized toucans that, together with the saffron toucanet, make up the genus ''Pteroglossus''. They are brightly plumaged and have enormous, contrastingly patterned bills. These birds are reside ...

's). The modern genera

evolved Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...

(like many other living genera of birds) around the Oligocene-Miocene boundary about 23 Mya. '' Microsula'', which lived during that time, seems to have been a primitive booby that still had many symplesiomorphies with gannets. Like the other Phalacrocoraciformes, the sulids originated probably in the general region of the

Atlantic The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe an ...

or western

Tethys Sea The Tethys Ocean ( el, Τηθύς ''Tēthús''), also called the Tethys Sea or the Neo-Tethys, was a prehistoric ocean that covered most of the Earth during much of the Mesozoic Era and early Cenozoic Era, located between the ancient continents ...

– probably the latter rather than the former, given that their earliest fossils are abundant in

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a subcontinent of Eurasia and it is located entirel ...

, but absent from the well-studied contemporary American deposits. Prehistoric sulids (or suloids) only known from

s are: * '' Masillastega'' (Early Eocene of Messel, Germany) – may belong in ''Eostega'' * '' Eostega'' (Late Eocene of Cluj-Manastur, Romania) – may include ''Masillastega'' * Sulidae gen. et sp. indet. (Thalberg Late Oligocene of Germany) – ''Empheresula''? * Sulidae gen. et sp. indet. (Late Oligocene of South Carolina, United States) – ''Microsula''? * '' Empheresula'' (Late Oligocene of Gannat, France – Middle Miocene of Steinheimer Becken, Germany) – including ''"Sula" arvernensis'', ''"Parasula"'' * '' Microsula'' (Late Oligocene of South Carolina, United States – Grund Middle Miocene of Austria) – may belong in ''Morus'' or ''Sula'', includes ''"Sula" avita'', ''"S." pygmaea'', ''Enkurosula'', ''"Pseudosula"'' * '' Sarmatosula'' (Middle Miocene of Credinţa, Romania) * '' Miosula'' (Late Miocene of California) * '' Palaeosula'' (Early Pliocene? of California) * '' Rhamphastosula'' (Pisco Early Pliocene of SC Peru) * '' Bimbisula'' (middle Pliocene of South Carolina) * Sulidae gen. et sp. indet. (Late Pliocene of Valle di Fine, Italy) – ''Morus''?A proximal humerus fragment somewhat similar to a gannet's: Lambrecht (1933: p.286) For prehistoric

of the extant genera, see the genus articles. The

Early Oligocene The Rupelian is, in the geologic timescale, the older of two ages or the lower of two stages of the Oligocene Epoch/ Series. It spans the time between . It is preceded by the Priabonian Stage (part of the Eocene) and is followed by the Chattian ...

'' Prophalacrocorax ronzoni'' of Ronzon, France, was variously placed in the

seaduck The sea ducks (''Mergini'') are a tribe of the duck subfamily of birds, the Anatinae. The taxonomy of this group is incomplete. Some authorities separate the group as a subfamily, while others remove some genera. Most species within the group sp ...

genus '' Mergus'', in ''Sula'', and after a distinct genus was established for it, in the Phalacrocoracidae. While it is quite likely to belong in the Sulae and may have been an ancient sulid (or suloid), of the three placements explicitly proposed, none seems to be correct.Göhlich, Ursula B. (2003): The avifauna of the Grund Beds (Middle Miocene, Early Badenian, northern Austria). ''Annalen des Naturhistorischen Museums Wien A'' 104: 237-249 nglish with German abstractbr>PDF fulltext
/ref>

References

External links

Live camera from Eldey IcelandSulidae videos
on the Internet Bird Collection

{{Authority control Bird families Taxa named by Ludwig Reichenbach Extant Ypresian first appearances