Population Estimates for Selected Breeding Seabirds at Kilauea Point National Wildlife Refuge, Kauai, in 2019

Kilauea Point National Wildlife Refuge (KPNWR) is an important seabird breeding site located at the northeastern tip of Kauai in the main Hawaiian Islands (MHI). Despite the regional significance of KPNWR as one of the most important breeding sites for Red-tailed Tropicbirds (Phaethon rubricauda), Red-footed Boobies (Sula sula), and Wedge-tailed Shearwaters (Ardenna pacifica) in MHI, robust and accurate population surveys have not been consistently conducted and recent information is lacking. In this study, we completed comprehensive population surveys for these three species during the 2019 breeding season. Using direct censusing methods (ground-searching, visual and photographic counts), we determined that 387 Red-tailed Tropicbird and 5,049 Red-footed Booby breeding pairs nested at KPNWR in 2019. Additionally, we performed surveys of aerially displaying tropicbirds to estimate a potential population of 30 White-tailed Tropicbird (P. lepturus) breeding pairs at KPWNR. Using a stratified-random plot-sampling method, we estimated that 20,998 Wedge-tailed Shearwater pairs nested at KPNWR in 2019. The breeding population size results in this study are greater than those reported in the past for KPNWR. We suggest that the Red-tailed Tropicbird breeding population has increased since the mid-2000s (when population estimates were last made), whereas Red-footed Booby numbers have likely remained similar and 2019 results show an increase over past estimates because of the more comprehensive methods used in this study. The results of these surveys provide current and accurate population sizes for these species that can serve as 1) benchmarks for future management and monitoring at KPNWR, and 2) important components of population-level assessments of seabird vulnerability to potential offshore wind energy development in the MHI. The data provided in this release support all population estimates in this study.
The data are organized as:
1. RFBO_PhotoList: a tabular list of all photograph filenames and ancillary information (camera settings, location) used for conducting Red-footed Booby counts
2. RFBO_Photos: photographic images used for conducting Red-footed Booby counts and output software files of count results; photographs are grouped by sub-colony and platform (ground or aerial)
3. TropicbirdNests: a tabular list of all tropicbird nests, locations, and ancillary information
4. TropicbirdSearch: a polyline shapefile of all ground-based search effort for tropicbird nests created from GPS tracks of field crew
5. WTSH_plots: a tabular list of all survey plots, locations, and ancillary information used for estimating Wedge-tailed Shearwater population
6. WTSH_stratum: a polygon shapefile of sampling strata used for estimating Wedge-tailed Shearwater population

Detailed descriptions of data are found in each associated metadata file and additional information useful for interpreting these data can be found in the data series report:
Felis, J.J., Kelsey, E.C., Adams, J., Stenske, J.G., and White, L.M., 2020, Population estimates for selected breeding seabirds at Kilauea Point National Wildlife Refuge, Kauai, in 2019: U.S. Geological Survey Data Series 1130, 32 p., https://doi.org/10.3133/ds1130.