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Many seabird breeding colonies have recovered from heavy anthropogenic disturbance after conservation actions. The widely distributed red-tailed tropicbird, Phaethon rubricauda, was used as a model species to assess potential anthropogenic impacts on the genetic diversity of breeding colonies in the Pacific Ocean. Cytochrome c oxidase subunit I and control region sequences analyses were conducted across the range of the species in the Pacific Ocean. The study sites were at islands without human-related disturbance (non-impacted islands) and with human-related disturbance (impacted islands). We hypothesized that (i) breeding colonies of the red-tailed tropicbird on impacted islands have lower genetic diversity compared with colonies on non-impacted islands, and (ii) breeding colonies of the red-tailed tropicbird show significant fine and broad-scale genetic structure across the Pacific Ocean. Bayesian skyline analyses were conducted to infer past changes in population sizes. Genetic diversity was similar between impacted and non-impacted islands. There was significant broad-scale genetic structure among colonies separated by over 6,000 km, but a lack of significant fine-scale genetic structure within Australasia and Hawai'i, although a significant level of differentiation was found within Chile with ΦST analyses. Skyline analyses showed that effective population sizes remained relatively constant through time, but experienced either a slight decrease or the end of an expansion event through the last 1,000 years. These changes may be related to the arrival of humans on Pacific islands. Impacted islands may have received immigrants from other relatively close islands, buffering the loss of genetic diversity. However, it is also possible that colonies have retained ancestral variation or that a large effective population size coupled with a long generation time (13 years) has prevented the loss of genetic diversity in human-impacted islands. Future research using higher-resolution markers is needed to resolve the population genetic structure of the red-tailed tropicbird in an ecological time-scale.

Moku‘ae‘ae Rock Islet is located off the north shore of Kaua‘i and is protected as a Hawai‘i State Seabird Sanctuary. In the late 1970s it was also the site of a cross-fostering project for the endangered Newell’s Shearwater, Puffinus newelli . Few avifauna surveys have been undertaken on the islet, and none since 2007. In 2013 and 2015, we conducted burrow searches across the entire islet to obtain breeding population estimates for each species and to evaluate whether the Newell’s Shearwater had become established as a breeding species after the cross-fostering project. Auditory surveys were also conducted for 2 hr after sunset and 1.5 hr before sunrise, which are the peak calling periods for the Newell’s Shearwater on Kaua‘i. A total of seven seabird species was recorded on the islet, of which three, Bulwer’s Petrel, Bulweria bulwerii ; Wedge-tailed Shearwater, Ardenna pacifica ; and Red-tailed Tropicbird, Phaethon rubricauda , were confirmed breeding. This is the first time Bulwer’s Petrel has been confirmed breeding on Moku‘ae‘ae. Searches for Newell’s Shearwater did not produce evidence that this species breeds on the islet, suggesting that the cross-fostering project was not successful. Although the islet is small, it represents an important refuge for seabird species. However, high levels of depredation were recorded on Bulwer’s Petrel; we conclude that these were all killed by the introduced Barn Owl, Tyto alba , based on disposition of the bodies and the injuries they had sustained. Management recommendations for the islet include creation of a management plan, annual breeding bird surveys, annual rat monitoring, and Barn Owl control.

Disruption of pair-bonds and switching nest-site are associated with breeding failure in many seabirds. Both strategies can prevent repetition of poor performance with a low-quality mate or at a poor-quality nesting site. In the Red-tailed Tropicbird (Phaethon rubricauda), the relationship between mate-fidelity, nest-site fidelity and reproductive performance is poorly understood. We therefore examined this relationship in Red-tailed Tropicbirds, using data collected on Christmas Island in the Indian Ocean from 1984 to 1986, corresponding to three successive breeding seasons. Birds showed strong between-season mate-fidelity, despite previous breeding failure, and subsequent breeding success in birds faithful to their mate was significantly higher than in pairs that bred together for the first time, indicating that mate-fidelity may outweigh the costs of disruption of pair-bonds. Although switching of nest-site was more likely to occur after previous breeding failure, it did not increase subsequent breeding success, indicating that nest-site switching may not be advantageous in Red-tailed Tropicbirds on Christmas Island. Although effects of age, dispersal rates to inaccessible parts of the island and adult survival were not examined in this study, our results provide a valuable basis for the evaluation of population dynamics of Red-tailed Tropicbirds on Christmas Island.

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. Resumen: Globalmente, las aves marinas son vulnerables a amenazas antropogenicas tanto en el mar como en tierra. Las aves marinas tipicamente anidan en colonias y muestran alta fidelidad a las colonias natales, y tales colonias en islas de baja elevacion pueden ser amenazadas por el incremento del nivel del mar. Utilizamos French Frigate Shoals, el mayor atolon en el Archipielago Hawaiano, como un estudio de caso para explorar la dinamica poblacional de colonias de aves marinas y los efectos potenciales que puede tener el incremento del nivel del mar sobre estas colonias. Compilamos observaciones historicas, una serie de tiempo de 30 anos de la abundancia de poblaciones de aves marinas, elevaciones e imagenes aereas de todas las islas de French Frigate Shoals. Para estimar la dinamica poblacional de 8 especies de aves marinas que se reprodujeron en la Isla Tern de 1980 a 2009, utilizamos un modelo Gompertz con un metodo Bayesiano para inferir las tasas de crecimiento poblacional, la densodependencia, la variacion del proceso y el error de observacion. Todas las especies incrementaron en abundancia, en un patron que proporciono evidencia de la densodependencia. Es probable que Fregata minor, Sula dactylatra, Phaeton rubricauda, Onychoprion lunatus y Gygis alba se encuentren en capacidad de carga. La densodependencia puede exacerbar los efectos del incremento del nivel del mar sobre aves marinas porque las poblaciones cercanas a la capacidad de carga en una isla seran mas afectadas que poblaciones con espacio para crecer. Proyectamos que 12% de French Frigate Shoals se inundara si el nivel del mar incrementa 1 m y 28% si el nivel del mar incrementa 2 m. Onychoprion lunatus y especies que anidan en arbustos son especialmente vulnerables al incremento del nivel de mar, pero diques y la restauracion de habitat pueden mitigar los efectos del incremento del nivel del mar. Las perdidas de habitat para la anidacion de aves marinas puede ser sustancial en las Islas Hawaianas en 2100 si el nivel del mar incrementa 2 m. La restauracion de colonias de aves marinas en sitios mas elevados representa una solucion mas perdurable para la conservacion de aves marinas del Pacifico.

In the tropical marine environment food resources are scarce and often patchily distributed. Consequently, nesting tropical seabirds must balance travelling to productive areas and sharing incubation or providing food to the chick. Changes in foraging behaviour occur when adults switch from feeding only for themselves during incubation to feeding a chick and fulfilling their own energy requirements. Externally attached data-devices were used to compare the duration of foraging trips, flight activity and depth of dives of incubating and chick-rearing Red-tailed Tropicbirds (Phaethon rubricauda) on Christmas Island, Indian Ocean. Adults with chicks had a bimodal pattern of foraging, with alternating short and long foraging trips (mean duration ± s.d. of short trips = 3.0 ± 4.1 h, of long trips = 57.4 ± 41.1 h), whereas incubating adults undertook only longer trips (mean duration ± s.d. = 152.9 ± 47.2 h). This strategy is stimulated by partner behaviour, rather than body mass as reported for many other seabirds, and may enable the optimisation of simultaneous food delivery to chicks and self-feeding when local resources are poor. The proportion of time spent in flight (flight activity) by adults with chicks averaged 90.1% during short trips whereas incubating birds spent only 62.4% of their trips flying. Overall mean depth of foraging dives by adults with chicks averaged 0.6 ± 0.3 m during short trips; mean maximum depth of dives by incubating adults were recorded using maximum-depth recorders and were significantly deeper at 10.7 ± 8.7 m, reaching a maximum depth of 25.6 m.

Round Island (19°51'S, 57°47'E), an uninhabited volcanic islet lying 14 miles NNE of the Mauritian mainland, provides locally important breeding grounds for four species of seabirds; the Trindade Petrel Pterodroma arminjoniana, the Wedge-tailed Shearwater Puffinus pacificus, the Red-tailed Tropic Bird Phaethon rubricauda and the White-tailed Tropic Bird Phaethon lepturus. The landing conditions on the island are notoriously difficult and prior to 1975, visits by naturalists had been limited to short stays, a few days at the most. Accounts of the natural history of the island have been made by Vinson (1965), Bullock (1977) and Bullock & North (1984). This paper gives the results of studies on the breeding biology of the Trindade Petrel during two visits to Round Island from 27 July to 2 September 1978, and from 30 July to 18 August 1982.

The Bonin Islands provide breeding habitat for many species of seabird, but detailed information on breeding sites is unavailable. Here, we describe the recent species composition of breeding seabirds on 66 islands. A total of 15 species (Diomedea immutabilis, D. nigripes, Pterodroma hypoleuca, Bulweria bulwerii, Puffinus pacificus, Oceanodroma tristrami, O. matsudairae, Phaethon rubricauda, Sula leucogaster, S. dactylatra, S. sula, Thalasseus bergii, Sterna fuscata, Anous stolidus and A. minutus) was recorded breeding in the Bonin Islands based on field and literature surveys. The sole nesting record of S. sula was on a small island near Haha-jima, where it has failed to breed since a typhoon struck the island. We did not detect Puffinus lherminieri bannermani, although it bred on Kitaiwo-jima before World War II. S. leucogaster was the most widespread species and bred on 39 islands. The second most widespread species was P. pacificus, which bred on 35 islands. There was a positive relationship between species richness and island area. The distribution of breeding sites may be affected by human settlement and introduced species such as feral goats Capra aegagrus. Introduced animals should be controlled to protect the seabird fauna on the islands.

During spring and autumn 1980-95, we surveyed Red-tailed Phaethon rubricauda, White-tailed P. lepturus and Red-billed Tropicbirds P. aethereus at sea in the Pacific between the coast of the Americas and 176°W. For the Pacific, we had complete coverage of the range of aethereus, but only partial coverage of that of rubricauda and lepturus. Six areas of higher density were indicated: three of rubricauda, two of lepturus and one of aethereus. After pooling data across years, the 'abundance' (total number including subadults and adults) estimate for rubricauda was 81 700 (boreal spring) and 86 500 (boreal autumn) birds. Abundance of each of the three rubricauda subpopulations differed between seasons by about 50% despite seasonal consistency when populations were grouped. Furthermore, high densities of rubricauda occurred at the edge of our study area, indicating that neither of the seasonal estimates for this species could be considered as total numbers. Abundance estimates of lepturus during the non-breeding season (when these birds had dispersed from colonies) were 11 000 and 41 500 birds for northern and southern populations, respectively. Estimated abundance of aethereus during the boreal spring was 26 700 birds, and 33 400 during the boreal autumn. Because tropicbirds are attracted to survey vessels, we also estimated the abundance after excluding those recorded as flying in a steady direction, or having been attracted to the ship. Considering only stationary birds (i.e. those that could not have been attracted), our minimum estimates were 41 000 rubricauda, 15 750 aethereus, 28 000 southern lepturus and 6400 northern lepturus.

International audience; We studied seasonal and inter-annual variations in the diet, amount of food delivered to chicks, and body condition of chicks and adult red-tailed tropicbird at Europa Island (Mozambique Channel, Indian Ocean), during 3 consecutive seasons. The diet consisted of epipelagic fishes (13 families) and squid (3 families) totalling 32 taxa. Three families, the squid Ommastrephidae (mainly Sthenoteuthis oualaniensis) and the fishes Exocoetidae (flying-fish) and Coryphaenidae (dolphinfish), accounted for 68% of the number of prey and 83% of the ingested biomass. There were considerable differences in size and mass of the prey items, dolphin fish being the largest and squid the smallest. There were important seasonal variations in diet. During chick-rearing, 41% of the mass of food delivered to chicks consisted of dolphin fish, whereas these fish represented only 2% of the mass of food during incubation. The squid were caught in similar proportion throughout the breeding season but were larger during chick rearing. We did not find any inter-annual variation in the diet of chicks, nor in the body condition of either fledglings or adults, suggesting that no major inter-annual changes in food availability occurred during the course of our study. However, there was some interannual variation in feeding frequency and body condition of chicks of less than 60 d. There were also significant day-to-day variations in the feeding frequency in one of the 3 seasons studied. This suggests that day-to-day variation in the marine environment or in foraging conditions may have shortterm consequences in the food provisioning and body condition of growing chicks, but that these variations do not necessarily result in long-term (inter-annual) variations in diet and body condition of fledgling or adult red-tailed tropicbirds at Europa island. These results suggest that between 1995 and 1997, red-tailed tropicbirds of Europa relied on predictable and seasonal food resources when breeding.

Anthropogenic impact has been heavy in remote oceanic islands, including the introduction of alien species, having negative effects on native seabirds. The isolated and subtropical Rapa Nui (Easter...

We reviewed the status of the breeding marine birds on San Benedicto Island, Mexico, based on >100 years of published observations and seven of our own surveys conducted between 1978 and 2000. We found that there have been marked changes in the island avifauna with two main trends evident. First, a volcanic eruption destroyed much of the island in 1952. The Wedge-tailed Shearwater (Puffinus pacificus; estimated breeding population 1,000 pairs), Townsend's Shearwater (Puffinus auricularis; probable breeder, small numbers), and Red-footed Booby (Sula sula; 60 pairs) historically had much larger populations, but they apparently never fully recovered from the eruption. The Masked Booby (Sula dactylatra; 2,185 pairs), however, has become much more abundant perhaps due to changes in the vegetation. The second trend is that within the last three decades at least two, and possibly four, species from the central Pacific have colonized the island. The Laysan Albatross (Phoebastria immutabilis; 12 pairs) started breeding in the late 1980s; Black-footed Albatross (Phoebastria nigripes; 1 pair) in 2000. Red-tailed Tropicbirds (Phaethon rubricauda; probable breeder, 10 pairs) may have started breeding in the 1980s, and at least some of the breeding Brown Boobies (Sula leucogaster; 300 pairs) are from central Pacific populations. The reason(s) for this influx of central Pacific species is unknown, but likely involves changes in the marine environment. Other breeding species include the Red-billed Tropicbird (Phaethon aethereus; 200 pairs), Nazca Booby (Sula granti; 50 pairs), Great Frigatebird (Fregata minor; 165 pairs), and Magnificent Frigatebird (Fregata magnificens; 5 pairs).

Suwarrow (Suvorov) atoll is an important seabird breeding site in the central Pacific Ocean. However, it is not protected and is attractive to developers of potentially damaging aquaculture industries. In this paper I report the results of a survey conducted to establish the present status of Suwarrow's seabird colonies and to generate base-line data for measuring the effect of a proposed pearl-farm development. Between late July and early September 2000 the reef islets were surveyed for seabird chick numbers and age-states using a simple sampling method. In addition to Sooty Tern Sterna fuscata, populations of boobies Sula spp., noddies Anous spp., frigatebirds Fregata spp. and tropicbirds Phaethon spp. were assessed. Results showed that bird populations were maintaining levels similar to those from findings of surveys in 1992. Of particular note were globally significant numbers of Lesser Frigatebird Fregata ariel and Red-tailed Tropicbird Phaethon rubricauda. Migratory birds were observed with Bristle-thighed Curlew Numenius tahitiensis regularly seen. The well-being of bird-life on the islets appears to be indirectly proportional to the proximity of human activity, with birds not observed breeding on Anchorage Island – the islet most often visited by people.

Tropical seabirds have evolved a wide range of breeding regimes to fit with their local environment. The western Indian Ocean shows various oceanic situations, providing opportunities to link variations in breeding phenology with variations of the environment. The breeding seasons of seabirds at Europa Island (Mozambique Channel, western Indian Ocean) are analysed. Three oceanic, tuna-associated species (the sooty tern Sterna fuscata, the red-footed booby Sula sula, and Audubon's shearwater Puffinus lherminieri) breed during austral winter (June–October), whereas the red-tailed tropicbird Phaethon rubricauda breeds during austral summer (November–April). During winter, sea-surface temperatures are the lowest, subtropical waters are the closest to the island, and long-line catches of tunas are important. Thermal fronts occur during winter, in relation to the northward shift of subtropical waters. This is known to be favourable to tunas, and I suggest that the winter breeding of sooty terns, red-footed boobies and Audubon's shearwaters is because of an increase in the abundance of tunas. Geographic variations in the breeding phenology of sooty terns in the western Indian Ocean largely support the hypothesis that sooty terns take advantage of cool subtropical waters, when those waters are within their foraging range. The red-tailed tropicbird is a solitary forager, not associated with tunas. During the chick-rearing period, 40% of the mass of food brought to the chicks consists of dolphin-fishes Coryphaena spp. Those warm water, surface dwelling fishes are known to migrate in relation to sea-surface temperatures. Seasonal changes in the occurrence or vulnerability of dolphin-fish in the Mozambique Channel may have favoured a summer breeding regime in red-tailed tropicbirds at Europa Island. Further studies of the marine life of seabirds are needed to test these hypotheses and to learn more about the foraging ecology of tropical seabirds.

We examined nest sites of Red-tailed Tropicbirds (Phaethon rubricauda) on Rose Island of the Rose Atoll National Wildlife Refuge, American Samoa, to determine habitat features important for nest-site selection of this species. We quantified habitat characteristics at 27 nest sites and at 27 random sites during September 1991. All nests were located under beach heliotrope (Messerschmidia argentea) shrubs or pisonia (Pisonia grandis) trees. Nest sites were placed farther under the nest shrub, had more stems in the nest space, and greater percent shade cover than random sites. Nest sites averaged 24.9 m from their nearest neighbor, ≥20 m greater than has been reported elsewhere for this colonial species. We suggest that an overpopulation of Polynesian rats (Rattus exelans) may have influenced nest-site selection by Red-tailed Tropicbirds on Rose Island.

Wing morphology of nine species of seabirds from Johnston Atoll in the central tropical Pacific was analyzed to determine how wing size and shape correlated with observed foraging behavior and, in some species, the energetic cost of flight. Red-tailed Tropicbirds (Phaethon rubricauda) and Christmas Shearwaters (Puffinus nativitatis) had lower wing areas, shorter wing spans, and higher relative wing loading than would be predicted from mass alone. Brown Noddies (Anous stolidus) and Red-footed Boobies (Sula sula) had lower wing loading, Brown Boobics (Sula leucogaster) and Sooty Terns (Sterna fuscata) had higher aspect ratios, and Brown Noddies had lower aspect ratio than would be predicted from mass alone. Aspect ratio showed greater intraspecific variation than the other variables. In most cases, predicted differences in wing morphology correlated well with observed foraging differences among species, and species that did not differ significantly in body mass differed with respect to wing size and shape; these morphological differences reflected varying flight and foraging behaviors. Sooty Terns had a higher aspect ratio and higher wing loading than Brown Noddies reflecting their more pelagic lifestyle, and Christmas Shearwaters had a lower aspect ratio and higher wing loading than Wedge-tailed Shear-waters (Puffinus pacificus) reflecting their pursuit plunging behavior.

Levels of environmental pollutants are usually higher in mainland and coastal areas than in offshore or oceanic islands due to higher inputs from agricultural and industrial sources. Levels of heavy metals are usually higher in adult than in young birds, because they have had longer to accumulate metals in their tissues, and/or because they may eat larger, more contaminated, prey. We examined the levels of arsenic, cadmium, chromium, lead, manganese, mercury, and selenium in the adults and young of Bonin petrel (Pterodroma hypoleuca), Christmas shearwater (Puffinus nativitatis) and red-tailed tropicbird (Phaethon rubricauda) on Midway Atoll, and adult wedge-tailed shearwater (Puffinus pacificus) on Midway Atoll and on Manana Island (off Oahu) in the northern Pacific. All birds were analyzed individually except for Christmas Shearwater chicks where samples were pooled to obtain sufficient quantities for analysis. Significant (p

A Red-tailed Tropicbird (Phaethon rubricauda) banded at Sugarloaf Rock (Western Australia) in January 1998 as a chick was recovered almost 6000 km away in September 2001 at Reunion Island as a non-breeding adult. This is the second case of transoceanic dispersion of Red-tailed Tropicbirds in the Indian Ocean. This recovery shows that this species can disperse over very large distances, following prevailing trade winds in the Indian Ocean, as found in the tropical Pacific Ocean.

From 1990 to 2000, the Johnston Atoll Chemical Agent Disposal System (JACADS) incinerated part of the U.S. stockpile of chemical weapons on Johnston Atoll, central Pacific Ocean, which also is a National Wildlife Refuge and home to approximately a half-million breeding seabirds. The effect on wildlife of incineration of these weapons is unknown. Using a multi-strata mark-recapture analysis, we investigated the effects of JACADS on reproductive success, survival, and movement probabilities of red-tailed tropicbirds (Phaethon rubricauda) nesting both downwind and upwind of the incineration site. We found no effect of chemical incineration on these tropicbird demographic parameters over the 8 years of our study. An additional 3 years of monitoring tropicbird demography will take place, post-incineration.

The diving ability of two tropical Pelecaniformes, the Red-footed Booby (Sula sula) and the Red-tailed Tropicbird (Phaethon rubricauda) was studied on Europa Island, southern Mozambique Channel, using capillary depth recorders fitted on breeding adults. Both species mainly exploited the first 4 m of the water column. Although such a depth can be reached solely by passive plunge diving, the range of depths reached by the two species suggests that they may, at least sometimes, use their feet and wings to perform active underwater pursuit swimming. Intra-specific comparison of the depth reached by Red-tailed Tropicbirds also suggests that this species may change its diving behavior seasonally.

This paper represents part of a study on the thermoregulatory responses of nesting sea birds to natural environmental conditions. The investigations were conducted on Midway Island. Our previous publications (Howell and Bartholomew, 1961a, 1961b) have dealt with Laysan and Black-footed albatrosses (Diomedea immutabilis and D. nigripes), Bonin Island Petrels (Pterodroma hypoleuca), and Wedge-tailed and Christmas Island shearwaters (Pufinus pacificus and P. nativitatis). Bailey (1956) gives a useful account of the natural history of these and other species found on Midway. In the course of visits to Midway Island in June and July, 1959 and 1960, we were able to obtain data on thermoregulation in the Red-tailed Tropic Bird (Phaethon rubricauda) and the Red-footed Booby (Sula sula). Aside from the work of Probine and Wodzicki (1955) on the Gannet (Sula bassana) and that of Bartholomew, Dawson, and O'Neill (1953) and Bartholomew and Dawson (1954) on pelicans (Pelecanus), we know of no quantitative studies on thermoregulation in pelecaniform birds.