1.6.1 Terrestrial

Introduced predators are one of the most devastating threats to bird species in the world, and their impact on seabirds on islands can be catastrophic. Seabirds breeding on islands are particularly vulnerable to introduced predators. This is due to a number of reasons. Seabirds have evolved without mammalian predators and thus are particularly naive and vulnerable to the threat they pose. This is coupled with the fact that invasive species are usually highly adaptable, can live in a wide range of environments and breed rapidly, meaning they can quickly become widespread. When they are introduced to a new place, they have usually left the diseases and predators that would have kept their numbers under control back in their home range. In the Pacific these species include cats, rats (multiple species including Polynesian, black and Norwegian), mongoose, pigs, goats, dogs, brown tree snake, and various ants (such as Yellow Crazy Ant and Little Fire Ant).
Habitats important to seabirds can be greatly affected by rural and urban development, conversion to plantations, agricultural expansion, mining and logging. This results in seabirds, especially burrowing seabirds, being largely confined to remote islands, small, rugged islets, or at high elevation on large islands which are less developed.
Introduced plants also impact breeding colonies of birds. Invasive species such as Australian tree fern, guava and ginger in Hawaii, for example, are rapidly taking over native vegetation in remote mountain breeding colonies for ‘ua’u (Hawaiian Petrel) and ‘a’o (Newell’s Shearwater), making it impossible for burrow nesting species to continue to use traditional colony areas.
Light attraction can have a significant impact on certain seabird species, particularly certain shearwaters and petrels. Light pollution can come from a wide range of sources including towns and cities, industry, transport networks, stadiums and sports fields. Light sources at sea (including oil rigs, merchant ships, cruise ships, and fishing vessels) can also lead to mass groundings of fledglings, which get grounded when they leave the darkness of breeding colonies for the first time, are attracted to lights and eventually end up on the ground (either through exhaustion or collision). Once grounded they typically cannot recover flight and die from predation, being run over by cars, or from starvation or dehydration. Bright lights in or near petrel and shearwater colonies can also ground adult birds.
Infrastructure collisions. This can be a particular threat to seabirds transiting between the sea and inland breeding colonies at night. Birds are not able to see powerlines or guy wires that stretch across their flight paths, and they collide with the lines and can either die instantly or are injured and die later in their colonies. For populations of rare inland breeding species this can be one of the most critical conservation issues as it can impact large numbers of adult birds. It is also one of the hardest threats to measure, as birds colliding with lines in the darkness are notoriously hard to quantify and require specialised methods.
Climate change is bringing about significant changes affecting seabirds in the Pacific:
- Low-lying atoll islands are very susceptible to rising sea levels and storm surge events.14 In these scenarios, entire colonies can be destroyed as the ground under them literally disappears. In some cases, this could lead to the eventual abandonment of the largest colonies of certain species. For example, sea level rise predictions suggest that millions-strong colonies of Laysan and Black-footed Albatross breeding on islands in Papahānaumokuākea (the North-western Hawaiian Islands) will soon become displaced. The combination of lost nests, reduced reproductive success, and displacement could quickly endanger a species’ long-term potential for survival.
- Burrowing seabirds can be at risk of extreme weather events, such as storms, causing landslips, erosion of burrow habitat and washout of adults, eggs, or chicks, depending on the time of year.
- Other potential impacts include increases in parasite loads, increase in disease risks and increases in ‘natural’ predators such as land crabs as they take advantage of different fruiting loads due to increase rainfall events in some locations.
Harvesting of chicks, adults and eggs are important traditional activities for several Pacific cultures and communities. However, where contemporary populations consist of small remnants or are rapidly declining, harvesting, especially poaching could hasten the extirpation of species in those places where it occurs.
Disease is a periodic threat to all seabird species, particularly those in dense colonies, and so greater potential for transmission. Outbreaks of disease (such as avian flu and avian pox) are often related to extreme climate events where birds are under stress, weakening their immune capabilities. Disease has the possibility to negatively impact seabird populations by dramatically increasing both adult and chick mortality and can happen within a very short period of time.
Data deficiency. Although not an obvious and tangible threat, the lack of knowledge of where some species breed, forage, migrate or overwinter and even key life history traits (e.g., Fiji and Beck’s Petrels, and Heinroth’s Shearwater) means action cannot be taken to halt a decline or even the extinction of a species.