title: Population dynamics of Hawaiian seabird colonies vulnerable to sea-level rise.
abstract: Globally, seabirds are vulnerable to anthropogenic threats both at sea and on land. Seabirds typically nest colonially and show strong fidelity to natal colonies, and such colonies on low-lying islands may be threatened by sea-level rise. We used French Frigate Shoals, the largest atoll in the Hawaiian Archipelago, as a case study to explore the population dynamics of seabird colonies and the potential effects sea-level rise may have on these rookeries. We compiled historic observations, a 30-year time series of seabird population abundance, lidar-derived elevations, and aerial imagery of all the islands of French Frigate Shoals. To estimate the population dynamics of 8 species of breeding seabirds on Tern Island from 1980 to 2009, we used a Gompertz model with a Bayesian approach to infer population growth rates, density dependence, process variation, and observation error. All species increased in abundance, in a pattern that provided evidence of density dependence. Great Frigatebirds (Fregata minor), Masked Boobies (Sula dactylatra), Red-tailed Tropicbirds (Phaethon rubricauda), Spectacled Terns (Onychoprion lunatus), and White Terns (Gygis alba) are likely at carrying capacity. Density dependence may exacerbate the effects of sea-level rise on seabirds because populations near carrying capacity on an island will be more negatively affected than populations with room for growth. We projected 12% of French Frigate Shoals will be inundated if sea level rises 1 m and 28% if sea level rises 2 m. Spectacled Terns and shrub-nesting species are especially vulnerable to sea-level rise, but seawalls and habitat restoration may mitigate the effects of sea-level rise. Losses of seabird nesting habitat may be substantial in the Hawaiian Islands by 2100 if sea levels rise 2 m. Restoration of higher-elevation seabird colonies represent a more enduring conservation solution for Pacific seabirds.
authors.affiliation: U.S. Geological Survey, Patuxent Wildlife Research Center, Laurel, MD 20708, USA. jhatfield@usgs.gov
authors.forename: Jeff S
authors.initials: JS
authors.lastname: Hatfield
authors.forename: Michelle H
authors.initials: MH
authors.lastname: Reynolds
authors.forename: Nathaniel E
authors.initials: NE
authors.lastname: Seavy
authors.forename: Crystal M
authors.initials: CM
authors.lastname: Krause
mesh_terms: D000818:Animals; D001717:Birds / Q000502:physiology*; D057231:Climate Change; D003247:Conservation of Natural Resources; D017753:Ecosystem; D006254:Hawaii; D062312:Islands; D011157:Population Dynamics; D012098:Reproduction