As spatial scale increases, z energy increases following a quadratic (scale², β = -13.96, SE= 0.16, p <0.0001 | scale, β= 24.12, SE= 1.15, p<0.0001); see Figure 3. Compared to the null scans, lapwing nest surrounds possessed higher 3D variation across all spatial scales (nest, β = 2.90, SE=0.12, p=0.00379) and variation increased with spatial scale at a faster rate for nest sites at the smaller spatial scales (nest:scale², β = 2.621, SE=0.04, p= 0.0089 | nest:scale, β = -2.029, SE=0.13, p= 0.042). Post hoc comparison of site management strategies showed the nests of sheep grazed fields had significantly lower 3D variation compared to other sites, while wet grassland sites had significantly higher 3D variation (see supplemental material) For scales below the size of the clutch, 3D energy originates from deviation in height between small vegetation (grasses) or from the substrate (large stones, gravel). The 3D energy of pastoral nest sites at higher spatial scales was more similar to those of the arable sites than their null sites, except for at sheep grazed sites. At scales above the size of the nest, high energy results from large clumps/mounds of weedy vegetation, trampling and sloping terrain (hills). On average, clutches were elevated 4.5cm above their local surroundings. There was no significant difference between management type and nest elevation; nest elevation was instead predicted by 3D energy of the surroundings (energy : elevation, β = 2.894, SE= 53.816, p = 0.00493).

Over the 2 years, we sampled the Avon Valley and Sussex Sites we photographed 115 lapwing nests, 86 of which were scanned. Of the nests found, 13 (8 in 2021, 5 in 2022) were predated. The proportion of nests predated varied widely between county and site, with no predation events of scanned nests recorded in the Sussex sites. Though nest predation of unscanned nests did occur. Predation was the most common cause of nest failure, followed by abandonment. On average, predated nests had poorer colour matches and lower surrounding luminance complexity (SD). However, no significant result was observed and none of the camouflage metrics used were able to predict nest failure from predation (see supplementary material).

The percentage visibility (un-occluded) of the clutch (eggs only) increases with the observer viewing angle in a sigmoid fashion. On average, a viewing angle of 15^o elevation (equivalent Horizontal Distance: Fox 1.5m, corvid [6.0m, 11.9m, 23.9m, 47.8m, 95.5m]) is required for 25% visibility and an angle of 27^o (Horizontal Distance: Fox 0.8m, corvid [3.14m, 6.2m, 12.6m, 25.1m, 50.2m]) to see 50% (Figure 4). Increased 3D energy across spatial scales increases nest occlusion at low viewing angles (10 ^o -30 ^o), particularly at spatial scales below the clutch size, with the lower scales to the clutch having the largest effect (scale of grasses) on occlusion (See Supplemental Material).

The JND colour and luminance difference of the clutches from the local surround are in line with those of highly camouflaged animals (fox, lum ΔS μ 1.10 ± 0.02 SE | col ΔS μ 0.85 ± 0.02 SE) (Corvid, Lum ΔS, μ 0.9 ± 0.02SE | Col ΔS μ 1.58 ± 0.02 SE). Clutches were of a better colour match to bare crop and fallow sites as opposed to vegetated wet grassland sites for both visual systems (Sussex-Hampshire : corvid colour ΔS β= -6.33, SE= 0.87, p < 0.0001) (Sussex-Hampshire : fox colour ΔS, β= -7.43, SE= 0.80, p < 0.0001). ΔS colour and ΔS luminance follow a negative exponential with increasing viewing angle (Figure 4). For a decrease in viewing angle to drop ΔS colour and/or ΔS luminance by just 0.1 JND, the clutch would already be 75% occluded from most viewing heights. The exceptions were for corvid vision from a height of 12.8m (22.5 ^o for -0.1 JND) and 25.6m (32.5 ^o for -0.1 JND).