Habitat geometry rather than visual acuity limits the visibility of a ground-nesting bird's clutch to terrestrial predators

Data Collection Sites All images and 3D scans were collected from two separate locations monitored by the Game and Wildlife Conservation Trust (GWCT); the Avon Valley in Hampshire [50.93105,-1.78462] and Burpham in Sussex [50.87198, -0.51812]. Predation Data Nest predation status was determined using nest temperature loggers (iButtons) and weekly nest checks from the date of discovery to the point of failure or hatching following the methods of Hartman and Oring (Hartman & Oring, 2006). Predated eggshell fragments or disappearance of clutches/eggs prior to egg weight estimated hatch dates were encoded as predation events. Nest and Null Photography and Scanning From March to Mid-June of 2021 and 2022, we photographed 115 lapwing nests and 3D scanned 83. The nests were scanned with an ASUS Zenfone AR using the Matterport Scenes app from a height of 1.2m. Scans and photographs were taken from a height of 1.2 metres at a flat 90o (vertical) angle from the ground. For each nest, an additional nest-less photo and scan were taken at a distance of 1-2 metres (4 paces) from the nest, by backtracking in the direction of the approach to avoid further trampling the surrounding area. These additional photos and scans were used as a paired null for each nest. Photographs of the nests and nulls were taken using a chart colour-calibrated Sony A6000 with a Baader venus-u 52mm UV filter and the camera’s own visible light filter. A 7% and 93% uniform (λ 200–700nm) reflectance standard was placed in situ for each photograph. As the lighting environment was highly variable due to changes in solar angle and weather, all photos were taken with a 1m2 pop-out NEEWER diffuser sheet at times greater than 2 hours from dawn and dusk to prevent patterns from shadows changing the luminance and colour measurements of the clutches and their backgrounds. Photographs were converted to standardised multispectral images using the ‘generate multispectral image’ function within the MICA toolbox v2.2.2 for ImageJ. Dataset Generation 3D measures and colour measures for the scans and MSPEC images were generated using custom scripts for ImageJ available on our GitHub: The data frames for Z (depth) energy variation, 3D transects, colour metrics and occlusion metrics were combined with habitat and nest ID data using excel with additional filtering of damaged photographs and one non-subject species (redshank) within our R code.