Digital Imagery Used for Aerial Counts for Surface-Nesting Seabirds at Lehua Island and Moku Manu Islet and Ulupa'u Crater, O'ahu in 2019

This data release is a product of Atlas of Breeding Seabirds of the Main Hawaiian Islands (https://www.sciencebase.gov/catalog/item/5fc0045cd34e4b9faad7ef37). Specific results and details about methods and additional information useful for interpreting these data can be found in the data series report:
Adams, J., Kelsey, E.C., Stenske, J., and Felis, J.J., 2022, Aerial counts for surface-nesting seabirds at Lehua Island and Moku Manu Islet and Ulupau Crater, Oahu in 2019: U.S. Geological Survey Data Report 1161, 20p., https://doi.org/10.3133/dr1161.
We have incorporated the Hawaiian language spellings of place names however, software limitations did not allow for inclusion of the appropriate diacritical markings.
Among important seabird breeding sites in the main Hawaiian Islands (MHI), Lehua Island off Niihau, and Moku Manu Islet off Oahu support diverse and abundant seabird breeding populations. Both offshore islands provide excellent nesting habitat for surface nesting boobies (Sula spp.) and Moku Manu also supports nesting habitat for relatively large breeding populations of Sooty Tern (Onychoprion fuscatus) and Brown Noddy (Anous stolidus). Additionally, Ulupau Crater, near Moku Manu on Oahu, is one of only a few main island sites and the only site on the main island of Oahu that supports a nesting population of Red Footed Boobies (Sula sula). In May 2019, we completed comprehensive digital aerial photographic surveys at these three sites for six surface-nesting seabird species: Brown Booby (Sula leucogaster), Red-footed Booby, Masked Booby (S. dactylatra), Great Frigatebird (Fregata minor), Sooty Tern, and Brown Noddy.
We took oblique digital aerial photographs of Lehua during the late morning of 13 May from a H-65 Dolphin helicopter with the door open to provide the best viewing conditions. During the late morning on 16 May 2019, we worked with U.S. Coast Guard Auxiliary on-board a Piper Saratoga fixed-wing aircraft (single-engine, low-wing) to photograph the Red-footed Booby colony in Ulupau Crater and the entire surface of Moku Manu taken through a tinted, rear Plexiglas window. We used a Canon 5DSr camera (51-megapixel full frame) equipped with a Canon electro-focus (EF) ultra-sonic motor (USM) 135-mm telephoto lens for all photography. At all locations, we flew at an altitude of approximately 300 m above sea level and photographs were taken over distances of 150-850 m from bird subjects, resulting in pixel resolutions of 0.5-2.6 cm pixel-1 on the ground. Photographs were taken with overlap so that observers could later ensure locational reference and complete counting without double-counting. GPS coordinates of the location from where photos were captured were recorded from a GPS track recorded during photographic surveys.
We reviewed photographs and counted birds using the program DotDotGoose (Ersts 2019). We estimated 5,782, 102, and 1,446 nesting pairs of Red-footed Boobies at Lehua, Ulupau Crater, and Moku Manu, respectively. At Lehua and Moku Manu we estimated 692 and 65 nesting pairs of Brown Boobies, respectively. At Moku Manu we estimated 95 nesting pairs of Masked Boobies, one of only 3 nesting locales for this species in the MHI. Based on photo counts of sampled areas and area-based extrapolation, we estimated 17,938 terns (mostly Sooty Tern and including Brown Noddy) on Moku Manu. We observed Great Frigatebirds (Fregata minor) roosting at the two island sites, but we did not detect any sign of nesting for this species. The nesting population sizes of boobies across the three colonies and number of terns present on Moku Manu presented here likely are minimum estimates because individuals among these species can exhibit asynchronous nesting phenologies, and not all members of the nesting populations would be expected to be attending the sites when we surveyed. The results of these surveys provide current and accurate abundance estimates for these species that can serve as benchmarks for future management and monitoring and as important components of population-level assessments aimed at quantifying seabird vulnerability to potential offshore wind energy development in the MHI.
The DotDotGoose software interface requires that photos being counted are organized in a single folder and creates a .pnt output file referencing all photos in the folder and the locations (in pixel space) and classification of each object identified by the user. This data release maintains that structure for each unique colony photo set (Lehua, Moku Manu, and Ulupau Crater). The .pnt files in each folder can be opened in DotDotGoose to see classification results and locations of birds identified in each photo.
The data are organized as:
PhotoIndex: a tabular list of all photograph filenames and ancillary information (e.g., camera settings, location) used for the aerial photographs
DigitalImages: digital photographic images used for conducting aerial photographic counts and output software files of count results; photographs are grouped by location

References
Ersts, P.J., 2020, DotDotGoose (version 1.5.1): American Museum of Natural History, Center for Biodiversity and Conservation, accessed May 30, 2020, at https://biodiversityinformatics.amnh.org/open_source/dotdotgoose/

Felis J.J., Kelsey E.C., Adams J., Stenske J.G. , 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.