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Characterising patterns of habitat use is an important first step for effective conservation planning. Species restricted to low-lying islands are at greatest risk from climate change-related sea level rise, and requirements for breeding and foraging habitat may determine their risk from tidal inundation. The endangered Micronesian Scrubfowl (Megapodius laperouse senex) is a model species for understanding these impacts. This species faces the cumulative challenges of tourist visitation, invasive species, and rising sea levels, yet little is understood about its habitat use in the Rock Islands Southern Lagoon Conservation Area (RISL) of Palau. We studied the habitat requirements of this mound-nesting scrubfowl as a representative of a group of birds considered highly vulnerable to climate change. Analysis of 15 habitat variables at 24 incubation mounds and 26 randomly chosen sites indicated that scrubfowl selected incubation sites that were close to shore, contained large trees, and exhibited greater canopy heights than the surrounding forest. Birds preferentially built mounds at the base of large ironwood trees (Casuarina equisetifolia) but selected sites with significantly more breadfruit trees (Artocarpus mariannensis) than random. Scrubfowl foraged in a non-preferential manner, making use of all littoral strand forest habitat. Direct anthropogenic habitat loss is not a major threat to scrubfowl in the RISL but their breeding habitat is highly vulnerable to climate change-driven sea level rise.

Characterizing patterns of habitat use is an important first step for effective conservation planning. Species restricted to low-lying islands are at greatest risk from climate change-related sea level rise, and requirements for breeding and foraging habitat may determine their risk from tidal inundation. The endangered Micronesian Scrubfowl (Megapodius laperouse senex) is a model species for understanding these impacts. This species faces the cumulative challenges of tourist visitation, invasive species, and rising sea levels, yet little is understood about its habitat use in the Rock Islands Southern Lagoon Conservation Area (RISL) of Palau. We studied the habitat requirements of this mound-nesting scrub-fowl as a representative of a group of birds considered highly vulnerable to climate change. Analysis of 15 habitat variables at 24 incubation mounds and 26 randomly chosen sites indicated that scrubfowl selected incubation sites that were close to shore, contained large trees, and exhibited greater canopy heights than the surrounding forest. Birds preferentially built mounds at the base of large ironwood trees (Casuarina equisetifolia) but selected sites with significantly more breadfruit trees (Artocarpus mariannensis) than random. Scrubfowl foraged in a non-preferential manner, making use of all littoral strand forest habitat. Direct anthropogenic habitat loss is not a major threat to scrub-fowl in the RISL, but their breeding habitat is highly vulnerable to climate change-driven sea level rise.

Characterizing patterns of habitat use is an important first step for effective conservation planning. Species restricted to low-lying islands are at greatest risk from climate change-related sea level rise, and requirements for breeding and foraging habitat may determine their risk from tidal inundation. The endangered Micronesian Scrubfowl (Megapodius laperouse senex) is a model species for understanding these impacts. This species faces the cumulative challenges of tourist visitation, invasive species, and rising sea levels, yet little is understood about its habitat use in the Rock Islands Southern Lagoon Conservation Area (RISL) of Palau. We studied the habitat requirements of this mound-nesting scrub-fowl as a representative of a group of birds considered highly vulnerable to climate change. Analysis of 15 habitat variables at 24 incubation mounds and 26 randomly chosen sites indicated that scrubfowl selected incubation sites that were close to shore, contained large trees, and exhibited greater canopy heights than the surrounding forest. Birds preferentially built mounds at the base of large ironwood trees (Casuarina equisetifolia) but selected sites with significantly more breadfruit trees (Artocarpus mariannensis) than random. Scrubfowl foraged in a non-preferential manner, making use of all littoral strand forest habitat. Direct anthropogenic habitat loss is not a major threat to scrub-fowl in the RISL, but their breeding habitat is highly vulnerable to climate change-driven sea level rise.

Invasive predators have decimated island biodiversity worldwide. Rats (Rattus spp.) are perhaps the greatest conservation threat to island fauna. The ground nesting Palau Micronesian Scrubfowl Megapodius laperouse senex (Megapodiidae) inhabits many of the islands of Palau's Rock Island Southern Lagoon Conservation Area (RISL) in the western Pacific. These islands are also heavily visited by tourists and support populations of introduced rats, both of which may act as added stressors for the scrubfowl. Using passive chew-tag and call playback surveys on five tourist-visited and five tourist-free islands, we investigated if rats and tourists negatively affect scrubfowl, and if higher rat activity is associated with tourist presence. Rat detection probability and site occupancy were significantly higher on tourist visited (89% and 99%, respectively) compared to tourist-free islands (52% and 73%). Scrubfowl were detected at significantly more stations on tourist-free (93%) than tourist visited (47%) islands and their relative abundance was higher (2.66 and 1.58 birds per station, respectively), although not statistically significantly. While rat occupancy probability likewise had a non-significant negative effect on scrubfowl numbers across islands, our results show a negative relationship between tourist presence and scrubfowl in the RISL. Our findings also suggest that rat populations may be augmented by tourist visitation in the RISL. Although this situation may not seriously affect the scrubfowl, it may be highly detrimental to populations of other threatened island landbirds.

Climate change has been a subject of numerous studies. While findings suggest that most biological taxa will be affected by its manifestations, aspects of a species life history may increase its susceptibility to climate change. Given their reliance on environmental sources of heat to incubate their eggs, I examined the vulnerability to climate change of the avian family Megapodiidae. I also assessed habitat use, susceptibility to sea level rise, and the effect of introduced rats and tourist presence, as added stressors to climate change, on the Micronesian Megapode (Megapodius laperouse senex) in Palau. Based on available literature, I employed a trait-based assessment to investigate the vulnerability of 21 species of megapodes to climate change. All species were predicted to experience at least a 2°C increase in mean annual temperature, 12 may experience a moderate or greater fluctuation in rainfall, and 16 would be exposed to rising seas. While the most vulnerable megapodes are intrinsically rare and range restricted, mound nesting species may be more resilient to climate change than others. I examined breeding and foraging habitat use by the mound nesting megapode in the Rock Islands Southern Lagoon Conservation Area (RISL), where it almost exclusively uses low-lying littoral strand habitat for breeding. Megapodes preferentially selected sites that were 1) relatively close to shore, 2) contained large trees, and 3) exhibited greater canopy heights than the surrounding forest. The subspecies foraged in a non-preferential manner and used all littoral habitat with no apparent influence of dominant plant species composition. Using GIS and the latest spatial data, I modelled the effect of three currently accepted scenarios (0.52 m, 0.98 m, and 1.9 m) of sea level rise on their known breeding habitat. The RISL is comprised of 3,857.5 ha of forested cover of which megapodes used 120.8 ha (3.1%) for breeding, with an additional 25.3 ha potentially available to them. Meg

Remote tropical oceanic islands are of high conservation priority, and they are exemplified by range-restricted species with small global populations. Spatial and temporal patterns in rainfall and plant productivity may be important in driving dynamics of these species. Yet, little is known about environmental influences on population dynamics for most islands and species. Here we leveraged avian capture-recapture, rainfall, and remote-sensed habitat data (enhanced vegetation index [EVI]) to assess relationships between rainfall, vegetation greenness, and demographic rates (productivity, adult apparent survival) of three native bird species on Saipan, Northern Mariana Islands: rufous fantail (Rhipidura rufifrons), bridled white-eye (Zosterops conspicillatus), and golden white-eye (Cleptornis marchei). Rainfall was positively related to vegetation greenness at all but the highest rainfall levels. Temporal variation in greenness affected the productivity of each bird species in unique ways. Predicted productivity of rufous fantail was highest when dry and wet season greenness values were high relative to site-specific 5-year seasonal mean values (i.e., relative greenness); while the white-eye species had highest predicted productivity when relative greenness contrasted between wet and dry seasons. Survival of rufous fantail and bridled white eye was positively related to relative dry-season greenness and negatively related to relative wet-season greenness. Bridled white-eye survival also showed evidence of a positive response to overall greenness. Our results highlight the potentially important role of rainfall regimes in affecting population dynamics of species on oceanic tropical islands. Understanding linkages between rainfall, vegetation, and animal population dynamics will be critical for developing effective conservation strategies in this and other regions where the seasonal timing, extent, and variability of rainfall is expected to change in the coming decades

The western Pacific island of Rota is the fourth largest human-inhabited island in the Mariana archipelago and designated an Endemic Bird Area. Between 1982 and 2012, 12 point-transect distance-sampling surveys were conducted to assess bird population status. Surveys did not consistently sample the entire island; thus, we used a ratio estimator to estimate bird abundances in strata not sampled during every survey. Trends in population size were reliably estimated for 11 of 13 bird species, and 7 species declined over the 30-y time series, including the island collared-dove Streptopelia bitorquata, white-throated ground-dove Gallicolumba xanthonura, Mariana fruit-dove Ptilinopus roseicapilla, collared kingfisher Todiramphus chloris orii, Micronesian myzomela Myzomela rubratra, black drongo Dicrurus macrocercus, and Mariana crow Corvus kubaryi. The endangered Mariana crow (x̄ = 81 birds, 95% CI 30–202) declined sharply to fewer than 200 individuals in 2012, down from 1,491 birds in 1982 (95% CI = 815–3,115). Trends increased for white tern Gygis alba, rufous fantail Rhipidura rufifrons mariae, and Micronesian starling Aplonis opaca. Numbers of the endangered Rota white-eye Zosterops rotensis declined from 1982 to the late 1990s but returned to 1980s levels by 2012, resulting in an overall stable trend. Trends for the yellow bittern Ixobrychus sinensis were inconclusive. Eurasian tree sparrow Passer montanus trends were not assessed; however, their numbers in 1982 and 2012 were similar. Occupancy models of the 2012 survey data revealed general patterns of land cover use and detectability among 12 species that could be reliably modeled. Occupancy was not assessed for the Eurasian tree sparrow because of insufficient detections. Based on the 2012 survey, bird distribution and abundance across Rota revealed three general patterns: 1) range restriction, including Mariana crow, Rota white-eye, and Eurasian tree sparrow; 2) widespread distribution, low abundance, includi

This is an author's accepted manuscript of: Radley, P. M., van Etten, E. J. B., Blake, D., & Davis, R. A. (2021). Breeding and feeding habitat selection by an island endemic bird may increase its vulnerability to climate change. Biotropica, 53(2), 422-432. https://doi.org/10.1111/btp.12885

This article has been published in a revised form in Bird Conservation International https://doi.org/10.1017/S0959270920000246

Ha, J., Cruz, J. B., Kremer, S., Camacho, V. A., & Radley, P. (2018). Trends in Avian Roadside Surveys over a 20-Year Period on Saipan, Commonwealth of the Northern Mariana Islands. Pacific Science, 72(1), 81-93. Available here.

Saracco, James F. (02.2016). "Linking Vital Rates of Landbirds on a Tropical Island to Rainfall and Vegetation Greenness". PloS one (1932-6203), 11 (2), p. e0148570. Available here

Radley, P. M., Davis, R. A., Dekker, R. W., Molloy, S. W., Blake, D., & Heinsohn, R. (2018). Vulnerability of megapodes (Megapodiidae, Aves) to climate change and related threats. Environmental Conservation, 45(4), 396-406. Available here

This is an Author's Accepted Manuscript of: Camp,R., Brinck, K., Gorresen, P., Amidon, F., Radley, P., Berkowitz, S., Banko, P. (2015) Current Land Bird Distribution and Trends in Population Abundance Between 1982 and 2012 on Rota, Mariana Islands. Journal of Fish and Wildlife Management: 6(2), 511-540.Available here