Photograph index, camera settings, and locational information for images used to count Red-footed Boobies (Sula sula) nesting at Kīlauea Point National Wildlife Refuge, Kauaʻi, in 2019

During 13-18 May, 2019, we censused red-footed boobies (Sula sula) at Kīlauea Point National Wildlife Refuge (KPNWR), Kauaʻi. To evaluate ground-based visual counts and assess variability among methods, we employed photographic techniques to count nesting red-footed boobies at KPNWR in three distinct sub-colony areas: Crater Hill East, Crater Hill Interior, and Crater Hill West (see associated data series report for delineation of sub-colony areas). For ground-based photos, we used a Sony a7rii camera (42 megapixel full-frame) equipped with a Sony 100-400mm F4.5-5.6G lens to allow sufficient resolution to count nests and birds. We achieved pixel resolutions (as a function of camera resolution, focal length, and distance to birds) of 0.28-0.91 cm pixel-1 for photos used for refuge-wide population estimates. In addition, photos of the one sub-colony (Crater Hill West) were taken at two focal lengths (100mm, 0.84-2.03 cm pixel-1; 300mm, 0.28-0.68 cm pixel-1) to test the effect of pixel resolution on nest counts. These photo sets were taken within 5 minutes of each other to minimize variability in numbers of roosting birds at the colony. Additionally, we collected oblique aerial photographs from a helicopter flying along the length, and just offshore, of red-footed booby nesting areas at KPNWR during the late morning on 13 May 2019. Aerial photographs were taken with a Canon 5DSr camera (51 megapixel full frame) equipped with a Canon EF USM 135-mm telephoto lens, resulting in pixel resolutions of 0.61-1.53 cm pixel-1. Both ground-based and aerial photos were taken with overlap between individual photos in each set so that observers could later ensure locational reference and complete counting without double-counting. GPS coordinates of the location from which photos were captured were recorded with a handheld GPS on the ground and from a GPS track recorded during flight for aerial photos. This table includes information for every photo used in analysis, including filename, relevant camera settings from exif information, and location from which photo was taken.

[
  "010:12"
]

[
  "geospatial"
]