18Wildlife Conservation Plan for Seabirds

18 Wildlife Conservation Plan for Seabirds

Chapter 5 Threats

In Australia, threats to seabird populations can generally be attributed to one of four broad categories: biological, climate, resource use or chemical. Key threats to the survival of Australian seabirds are identified in this section. The list is not exhaustive but identifies the main threats that are likely to affect seabird populations adversely.

Habitat loss

Coastal development

Development pressures affect many species as human populations grow and we expand our coastal and urban footprint. Coastal development such as housing estates, roads, ports, windfarms and industrial areas can reduce or eliminate areas for seabirds to breed and forage. Tourism or industry developments on offshore islands can also lead to a reduction of the area available for nesting seabirds like terns and shearwaters. Secondary impacts of coastal and urban development can include increased disturbance, roaming domestic pets, light pollution and energy infrastructure (covered below).

The settlement of offshore islands, such as the Cocos (Keeling) Islands, has led to a decline in the distribution of breeding seabirds. Before human occupation of the islands in the 19th century, seabirds bred on all Cocos (Keeling) atolls. Now the only significant seabird breeding colonies are restricted to Pulu Keeling National Park. The site regularly supports more than 30,000 pairs of Red-footed Booby; 15,000 Common Noddy and 3,000 Great and Lesser Frigatebirds.

Loss of areas that support large numbers of seabirds can cause disproportionate declines in seabird populations, as displaced birds are unable to find suitable replacement habitat. Similarly, incremental loss of smaller areas affects the broader conservation of habitat availability. In Australia, loss of important habitat reduces availability of foraging and roosting areas, affecting the ability of birds to build up energy stores necessary for successful migration and breeding. Some areas are also important year-round for juvenile birds, with loss of these habitats affecting future breeding populations of these species.

Wildlife Conservation Plan for Seabirds 19

Habitat may be lost due to a variety of activities that make the habitat unavailable to seabirds. These may include direct loss through clearing, inundation, infilling or draining (for example, for buildings or marine services such as harbours, marinas, ports or oil terminals) or indirect loss through changes to hydrology, water quality or vegetation structural changes near breeding and roosting areas (for example increased vegetation cover or encroachment of buildings).

When assessing a development proposal, all direct and indirect impacts that have, will have, or are likely to occur on a protected matter as a result of the action must be considered.

Habitat modification

Seabirds are sensitive to subtle changes to their habitat. In particular, many have specialised feeding techniques making them susceptible to slight changes in prey availability or to their foraging environments. An activity that reduces the ability of seabirds to use an area for breeding, roosting or foraging, or reduces the availability of food, degrades habitat may have adverse impacts on the population. These impacts include (among others):

 alteration of nesting trees, ground substrate or burrows, sand spits used for roosting or inshore feeding areas such as seagrass beds, estuaries and coastal wetlands;

 substantial loss of marine or estuarine vegetation which is likely to alter the dynamic equilibrium of sediment banks and mudflats;

 invasion of coastal weeds;

 livestock (i.e. trampling burrows) and fire management at nesting areas, including on islands;

 water pollution and changes to the water regime, including the construction of dams and water management;

 artificial changes to hydrological regimes that affect the productivity of the feeding environment (for example, changes in water depth); and

 exposure of acid sulphate soils changing the chemical balance of the area.