Sulidae

The bird family Sulidae comprises the gannets and boobies. Collectively called sulids, they are medium-large coastal seabirds that plunge-dive for fish and similar prey. The ten species in this family are often considered congeneric in older sources, placing all in the genus Sula. However, Sula (true boobies) and Morus (gannets) can be readily distinguished by morphological and behavioral 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.

Description

Sulids measure about 60 to 85 cm (24 to 33 in) in length and have a wingspan of about 140 to 175 cm (4.59 to 5.74 ft). 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, and thus their wing loading is high. Consequently, they are very streamlined, reducing drag, so their bodies are "torpedo-shaped" as well as somewhat flat.