Document ID: chunk:federal_register_of_legislation:F2022L00775:reg:4:p2
Version: federal_register_of_legislation:F2022L00775
Segment Type: reg
Provision Reference: reg 4 (pt 2/12)
Character Range: 13158–16146

Wildlife Conservation Plan for Seabirds 5
 Seabirds of Australia

 Diet and foraging behaviour

Seabirds have evolved to exploit different food resources in the world's oceans, and to a great extent, their physiology and behaviour have been shaped by their diet (Springer et al 2018). These evolutionary forces have often caused species in different families and even orders to evolve similar strategies and adaptations to the same problems, leading to remarkable convergent evolution, such as that between Northern Hemisphere auks and Southern Hemisphere penguins.
There are four basic feeding strategies, or ecological guilds, for feeding at sea: surface feeding, pursuit diving, plunge diving and kleptoparasitism; within these guilds there are multiple variations on the theme.
Many seabirds feed on the ocean's surface, as the action of marine currents often concentrates food such as krill, forage fish, squid or other prey items within reach of a dipped head. Surface feeders that swim often have unique bills adapted for their specific prey. Prions have special bills with filters called lamellae to filter out plankton from water (Brooke 2004), and many albatrosses and petrels have hooked bills to snatch fast-moving prey. Gulls have more generalised bills that reflect their more opportunistic lifestyle.
Pursuit diving exerts greater pressures (both evolutionary and physiological) on seabirds. Propulsion underwater can be provided by wings (as used by penguins, diving petrels and some other species of petrel) or feet (as used by cormorants). Many shearwaters are intermediate between the two, having longer wings than typical wing-propelled divers but heavier wing loadings than the other surface-feeding procellariids, leaving them capable of diving to considerable depths while still being efficient long-distance travellers (Shaffer et al. 2006). This is the dominant guild in polar and subpolar environments, as it is energetically inefficient in warmer waters. With their poor flying ability, many wing-propelled pursuit divers are more limited in their foraging range than other guilds, especially during the breeding season when young need regular feeding.
Gannets, boobies, tropicbirds and some terns engage in plunge diving, taking fast moving prey by diving into the water from flight. Plunge diving allows birds to use the energy from the momentum of the dive to combat natural buoyancy (caused by air trapped in plumage) (Ropert-Coudert et al. 2004), and thus uses less energy than the dedicated pursuit divers, allowing them to utilise more widely distributed food resources, for example, less productive tropical areas. Some plunge divers (as well as some surface feeders) are dependent on dolphins and tuna to push shoaling fish up towards the surface (Au et al. 1986).
Kleptoparasites are seabirds that steal food of other seabirds. Most famously, frigatebirds and skuas engage in this behaviour, although gulls, terns and other species will steal food