Product Code Database
The bird family Sulidae comprises the and booby. Collectively called sulids, they are medium-large coastal that plunge-dive for fish and similar prey. The 10 species in this family are often considered Conspecificity in older sources, placing all in the genus Sula. However, Sula (true boobies) and Morus (gannets) can be distinguished via morphological, ethology, and DNA sequence characters. Abbott's booby ( 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. Friesen, V.L.; Anderson, D.J.; Steeves, T.E.; Jones, H. & Schreiber, E.A. (2002): Molecular Support for Species Status of the Nazca Booby ( Sula granti). Auk 119(3): 820–826. English DOI: 10.1642/0004-8038(2002)1190820:MSFSSO2.0.CO;2 PDF fulltext
They have stout legs and webbed feet, with the web connecting all four toes. In some species, the webs are brightly colored and used in courtship displays. 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 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 and ), sulids have a well-developed preen gland whose waxy secretions they spread on their feathers for waterproofing and pest control. They moult their tail feathers irregularly and the 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 has been recorded.
All species feed entirely at sea, mostly on mid-sized fish and similarly sized marine (e.g. ). Many species feed communally, and some species follow to scavenge discarded bycatch and Chumming. 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 ethology traits of gannets and boobies differ considerably, but the Sulidae as a whole are characterized by several behavioral : 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.
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. At first, at least one parent is always in attendance of the altricial 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 ( 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.
The Sulae were traditionally included in the Pelecaniformes in its obsolete paraphyletic circumscription, but , the namesake family of the Pelecaniformes, are actually more closely related to , ibises and spoonbills, the hamerkop, and the shoebill than to the sulids and allies. In recognition of this, the Sulae have been proposed for separation in a new order Suliformes, which also includes the (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), 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.
| Northern gannet ( Morus bassanus) | Western Europe and North America | |
| Cape gannet ( Morus capensis) | West to Southwest African coast | |
| Australasian gannet ( Morus serrator or Sula bassana) | Australia and New Zealand | |
| Abbott's booby ( Papasula abbotti) | Christmas Island | |
| Blue-footed booby ( Sula nebouxii) | Eastern Pacific Ocean from California to the Galápagos Islands south into Peru | |
| Masked booby ( Sula dactylatra) | Tropical oceans between the 30th parallel north and 30th parallel south. In the Indian Ocean it ranges from the coastlines of the Arabian Peninsula and East Africa across to Sumatra and Western Australia | |
| Nazca booby ( Sula granti) | Eastern Pacific from the islands in Baja California to the Galápagos Islands and the Isla de la Plata in Ecuador and Malpelo in Colombia | |
| Brown booby ( Sula leucogaster) | Pantropical areas of the Atlantic and Pacific Oceans | |
| Red-footed booby ( Sula sula) | Most tropical areas of oceans, main exceptions being tropical areas of E Atlantic and SE Pacific, breeding on islands | |
| Peruvian booby ( Sula variegata) | Coast of South America from Peru to Chile |
The fossil record of sulids is quite extensive due to the many Miocene/Pliocene forms that have been recovered, but the lineage of sulids extends back to the Eocene, and all things (such as the Early Eocene frigatebird 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 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's). The modern genera evolution (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 with gannets. Like the other Phalacrocoraciformes, the sulids originated probably in the general region of the Atlantic or western Tethys Sea – probably the latter rather than the former, given that their earliest fossils are abundant in Europe, but absent from the well-studied contemporary United States deposits.
Prehistoric sulids (or suloids) only known from are:
For prehistoric species of the extant genera, see the genus articles.
The Early Oligocene Prophalacrocorax of Ronzon, France, was variously placed in the seaduck 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 English. PDF fulltext
|
|
