22Wildlife Conservation Plan for Seabirds

22 Wildlife Conservation Plan for Seabirds

The other active volcanoes nearest Australia are in Papua New Guinea, New Zealand, South Pacific, Indonesia and the Philippines. Gas-rich sticky magmas dominate the Asia Pacific, making composite volcanoes and calderas the most common varieties in the region. These types of volcanoes threaten lives, property, agricultural lands and livelihoods throughout south-east Asia and the Australian region. While volcanoes can impact seabird colonies from time-to-time by removing suitable nesting habitat, they can also create new habitat which is colonised over time as conditions change and improve.

Earthquake, tsunami and landslips

Earthquakes are the vibrations caused by rocks breaking under stress. The underground surface along which the rock breaks and moves is called a fault plane. Apart from causing shaking, earthquakes of magnitude 4.0 or greater can also trigger landslides, which can cause casualties. The larger the magnitude of the earthquake, the bigger the area over which landslides may occur. Undersea earthquakes can cause a tsunami, or a series of waves which can cross an ocean and cause extensive damage to coastal regions and nearshore seabird populations (Viera et al. 2006; Reynolds et al. 2015).

In areas underlain by water-saturated sediments, large earthquakes, usually magnitude 6.0 or greater, may cause liquefaction. The shaking causes the wet sediment to become quicksand and flow. Subsidence from this can cause buildings to topple, and the

sediment might erupt at the surface from craters and fountains.

Landslips caused by earthquakes or heavy rainfall, can impact habitat used by seabirds. For example, in 2016, a landslip caused by a 7.5 magnitude earthquake in New Zealand significantly impacted the breeding colony of the globally endangered Hutton’s Shearwater (Puffinus huttoni). Hutton’s Shearwaters are small seabirds endemic to New Zealand that breed only in the Seaward Kaikōura Ranges. They breed at two sites about 8 kilometres inland – Kowhai Stream and Shearwater Stream - at altitudes between 1200-1800 metres. They make burrows in loose soil amongst tussocks, where they spend nearly six months raising their chicks. After the earthquake struck, it was thought that up to 25 per cent of the population may have been crushed by the landslide. Surveys following the earthquake suggested that an estimated 20–30 per cent loss of breeding burrows had occurred but adults had returned to breed.

Invasive species

Invasive species are one of the primary threats to seabirds around the globe (Baker et al. 2002; Jones et al. 2008; Croxall et al. 2012). Mammals such as cats (Felis catus), rodents (Rattus spp.), European Red Fox, dogs (Canis familiaris) and pigs (Sus scrofa) predate adults, chicks and eggs and have caused localised extinctions. Goats (Capra hircus), cattle (Bos spp.) and rabbits (Oryctolagus cuniculus) alter breeding areas making them unsuitable for breeding or reducing breeding success. On Bird Island, Seychelles, the invasion of Yellow Crazy Ants (Anoplolepis gracilipes) led to an estimated 60,000 pairs of Sooty Tern (Onchoprion fuscatus), which nest in colonies on the ground, being displaced from their nesting sites and also caused the death of White Tern (Gygis alba) chicks (Feare 1999). Yellow Crazy Ants may also take over nesting sites of known tree-hollow nesting birds and the constant acid spraying behaviour of crazy ants causes injuries to seabird chicks. The Yellow Crazy Ant has been identified as a threat to breeding seabirds and other biological assets on Christmas Island. Control efforts are underway to reduce the impacts on wildlife including baiting and biological control.