Australian Biological Resources Study

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Family SULIDAE Reichenbach, 1849

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Family SULIDAE Reichenbach, 1849


Compiler and date details

R. Schodde CSIRO Australian National Wildlife Collection, Canberra, ACT, Australia

 

Introduction

Sulids are medium to large seabirds, the gannets and boobies, and are centred in tropical and subtropical waters although gannets are also found in temperate regions. There are ten species in three genera, six of which are Australian. Three genera are identifiable by morphological, behavioural and DNA sequence characters. They are not truly pelagic remaining coastal unless dispersing on migration or during post breeding. Australasian Gannets are migratory moving to and from New Zealand and Australia. Young birds may also disperse widely in an erratic movement. Boobies, however, are generally more sedentary.

Plumage is principally white with brown to black on the primaries and dorsal or head feathers; Sula leucogaster is counter-shaded, the upper body and neck are brown, the abdomen white. A gannet’s head has a yellowish hue and black lores. Juveniles are speckled and generally darker than adults. All have waterproofed plumage, and a well-developed preen gland. Sulids lack a brood patch but do have a gular sac. Female boobies, while of similar appearance to males, are larger.

The adult’s facial and gular skin is bare and that and the feet may be black, red or blue. Sulid eyes are situated slightly behind the bill, giving them wide binocular vision; the iris is often pale in colour. A sulid’s wings are long, narrow and pointed and set well back on their body; reduced flight muscles allow for plunge-diving when feeding. The tails are long and graduated. The bill is stout and conical, with serrated edges in some species; the palate is desmognathous and the nostrils have no exposed external nares — these close when the birds dive. This bill is conspicuously coloured and pointed; the upper mandible curves down slightly at the tip and can move upwards for larger prey. All have short, stout legs set far back on the body, and totipalmate webbing with a pectinate central toenail. In some species the webbing is brightly coloured and features during courtship.

Sulids are marine feeders, taking fish and similar-sized marine invertebrates; many feed communally and are capable of taking flying fish when they leave the water. Using binocular vision sulids are capable of flying higher than most seabirds to locate prey. Their flight involves a regular patrol of a selected area; on sighting prey they plunge-dive, moving their wings in an almost straight body alignment which gives them a streamlined appearance. This allows them to dive to ten metres below the surface followed by swimming that may take them a further 15 metres.

Vocalisations in boobies include different calls from each of the sexes. Males produce plaintive whistles and females trumpeting honks. Gannets, both male and female, give a variety of loud and raucous calls. Sulids exhibit several behavioural synapomorphies: before flight gannets point the bill upwards while boobies point theirs forward and when landing they point the bill downwards.

Sulids are highly colonial, giving complex displays particularly during pairing and nesting and then later in nest defence. Breeding is conducted on offshore islands and along continental coastlines. Included among their highly structured displays are headshaking, bill menacing, sky pointing, and greeting ceremonies. Boobies utilise their use colourful feet and wings during displays on the ground and in the air. They continually select the same nest site. Breeding can be annual or biennial depending on species and food availability. Males inspect the nesting colony from the air and then protect it by displays and fight. They attract the female using displays and calls. Nests may be located on cliff ledges, slopes, trees, or on the ground; ground nests are shallow depressions in accumulations of guano whereas tree nests are constructed of twigs. Most breed in small to large, dense colonies, often sharing the area with other marine avifauna. Both adults incubate using their feet like a brood patch. The feet are vascularised and the birds hold the eggs under their webs; incubation lasts 41-55 days.

An average clutch size is two (or up to four) for boobies whereas gannets lay one egg. The eggs are oval with a base colour of white, pale blue, green or pink, and all unmarked apart from nest staining and having a limey coating. On hatching, the nidicolous, naked young are brooded on webs of the parents' toes and young quickly acquire white down; chicks are altricial and remain, often unattended, in the nest a further 14-22 days. Usually only one reaches maturity due to frequent siblicide by the stronger of two chicks.

The Tasman Booby, Sula tasmani van Tets, Meredith, Fullagar & Davidson, 1988, is extinct and is known only from fossil remains. It was assigned the CAVS no. 0743.

 

General References

Campbell, B. & Lack, E. (eds) 1985. A Dictionary of Birds. Calton : T. & A.D. Poyser xxx 670 pp.

Carboneras, C. 1992. Family Sulidae. pp. 312–321 in del Hoyo, J., Elliott, A. & Sargatal, J. Handbook of the Bird of the World. Barcelona : Lynx Edicions Vol. 1 696 pp.

Christidis, L. & Boles, W.E. 2008. Systematics and Taxonomy of Australian Birds. Melbourne : CSIRO Publishing 288 pp.

Cracraft, J. 1985. Monophyly and phylogenetic relationships of the Pelecaniformes: a numerical cladistic analysis. Auk 102: 834-853

Friesen, V.L. & Anderson, D.J. 1997. Phylogeny and evolution of the Sulidae (Aves: Pelecaniformes): a test of alternative modes of speciation. Molecular Phylogenetics and Evolution 7: 252-260

Nelson, J.B. 1978. The Sulidae Gannets and Boobies. Oxford : Oxford University Press pp.

Nelson, J. Bryan 2003. Gannets and Boobies. pp. 82–87 in Perrins, C. The Firefly Encyclopedia of Birds. Oxford : Firefly Books pp.

Olson, S.L. & Warheit, K.I. 1988. A new genus for Sula abbottii. Bulletin of the British Ornithologists' Club 108: 9-12

Patterson, S.A., Morris-Pocock, J.A. & Friesen, V.L. 2011. A multilocus phylogeny of the Sulidae (Aves: Pelecaniformes). Molecular Phylogenetics and Evolution 58(2): 181–91

Peters, J.L. 1931. Check-list of the Birds of the World. Cambridge, Massachusetts : Harvard University Press Vol. 1 xviii +345 pp.

Sibley, C.G. & Ahlquist, J.E. 1990. Phylogeny and Classification of Birds. A Study in Molecular Evolution. New Haven : Yale University Press xxiii 976 pp.

Van Tets, G.F., Meredith, C.E., Fullagar, P.J. & Davidson, P.M. 1988. Osteological differences between Sula and Morus, and a description of an extinct new species of Sula from Lord Howe and Norfolk Islands, Tasman Sea. Notornis 35: 35-57

 

History of changes

Note that this list may be incomplete for dates prior to September 2013.
Published As part of group Action Date Action Type Compiler(s)
10-Nov-2020 AVES 10-Nov-2020 MODIFIED
28-Oct-2015 SULIDAE Reichenbach, 1849 28-Feb-2020 MODIFIED
10-Nov-2020 PELECANIFORMES 27-Aug-2014 MODIFIED Dr Wayne Longmore
12-Feb-2010 (import)