Climate change is listed as the third greatest threat to seabirds globally (Croxall et al. 2012). It is predicted to decrease the land area of low-lying Pacific islands and cause complete inundation of some islands (IPCC 1997) leading to substantial population declines (Hatfield et al. 2012). Hurricanes have been documented to cause severe population changes in the forest bird species on American Samoa, with some species seeing population decreases of more than 50% four months after a hurricane (Trail et al. 1992). Although no data for seabirds or long term predictions are available specific to this IBA climate change represents a potential threat to this site owing to the risk of future increased frequency of storms.
Invasive Alien Species represent the greatest threat to seabirds globally (Croxall et al. 2012), causing adult mortality and reduced productivity owing to egg and chick predation. Polynesian Rat is ubiquitous throughout the Pacific (IUCN SSC Invasive Species Specialist Group 2012) and is confirmed to be present along with brown rats and black rats (SPREP, 2000). Rats have been recorded predating adult seabirds as well as eggs and chicks (Kepler 1967). They have precipitated island extinctions in small-bodied, ground-nesting seabirds, but their impacts on larger or arboreal nesting seabirds appear to be lower (Atkinson 1985, Jones et al. 2008). Feral Cat, Feral Pig and Feral Goat are all plausible but unconfirmed residents. Each can potentially cause declines in seabird colonies, and ungulates can exacerbate the threat from other invasive mammals through habitat modification (Atkinson 1985, Rodríguez et al. 2006, Jones et al. 2008, Duffy 2010). Overall, invasive mammals are know to be present and are likely to be having a limiting effect on seabirds, or causing population declines.
Human disturbance and direct harvesting of seabirds are listed as threats to 26 and 23 of the 97 globally threatened seabirds respectively (Croxall et al. 2012). For Near Threatened and Least Concern species it is likely that human disturbance and consumption affect an even greater proportion, particularly of tropical species, for which major reductions in populations and/or breeding sites are increasingly indicated but seldom quantified, especially across the whole range of the many wide-ranging tropical seabird species (Croxall et al. 2012). Direct harvesting of forest bird species does occur at this site and is known to impact on populations after hurricane impacts (Trail et al. 1992). It is unknown if this direct harvesting affects the seabird populations. The sustainability of such harvests is unknown but it may represent a threat to this population.
Seabirds are highly visually oriented and known to become disorientated at night in the presence of artificial light (Bruderer et al., 1999). On archipelagos worldwide, thousands of fledglings of different petrel species are attracted to artificial lights during their first flights from nest-burrows to the sea, a phenomenon called ‘fallout’ (Reed et al. 1985, Telfer et al. 1987, Le Corre et al. 2002, Rodríguez & Rodríguez 2009, Miles et al. 2010, Rodrigues et al. 2011). Grounded birds are vulnerable to starvation, predation, dehydration and collision with vehicles. The prevalence of this potential threat at this site is not known but it may be having a negative impact.
BirdLife International (2020) Important Bird Areas factsheet: National Park of American Samoa - Tutuila. Downloaded from
http://www.birdlife.org on 25/05/2020.