2 MATERIALS AND METHODS

Study System:

The northern lapwing (Vanellus vanellus ) is a ground-nesting wader that commonly breeds in lowland wet grassland and arable sites across temperate Eurasia (Cramp and Brooks, 1992). The species is of conservation concern in the UK and mainland Europe as their populations have been in decline since the 1970s (Wilson et al., 2001). Unsustainable nest predation is cited as a barrier to population recovery (Evans, 2004; Laidlaw et al., 2021; Roos et al., 2018).Northern lapwing nests comprise shallow scrapes in bare ground or short mixed vegetation, lined with varying amounts of dead plant matter (Kubelka et al., 2019). Their nests are defended from predators by using a combination of mobbing, distractive displays, behavioural crypsis and egg camouflage (Salek and Cepáková, 2006). While positioning away from trees and around waterbodies also protects nests (Eglington et al., 2009; Kaasiku et al., 2022).
We sampled lapwing nests from sites in two separate locations monitored by the Game and Wildlife Conservation Trust (GWCT); the Avon Valley in Hampshire and Burpham in Sussex. The Avon Valley sites included a variety of habitats, predominantly under UK agri-environment schemes, such as wet grassland, marshland, pasture, and a restored ex-gravel quarry. Conversely, the Sussex sites consisted of arable fields in various stages of rotation between plough, spring cereal, and fallow. Predation was monitored at the sites using iButton (Thermochron iButton, Maxim Integrated Products, Inc., Sunnyvale, CA) nest temperature loggers and weekly nest checks (Hartman and Oring, 2006). Nest outcomes (hatched, abandoned, flooded, trampled and predated) were determined by both interpretation of nest temperature logger plots and accepted in-field techniques (Hartman & Oring, 2006; Sheldon et al., 2010). All sites utilised some form of predator control or management to protect wading birds. These varied in intensity and included deterrents such as electric fences and crow scarers and removal methods such as Larsen traps, tunnel traps, and shooting (Fletcher et al., 2010; Laidlaw et al., 2021; Malpas et al., 2013).

Ethics Statement:

Corresponding permissions were granted as part of a collaboration with the GWCT and were approved by the University of Exeter Ethics Committee.

3D Scanning & Calibrated Photography:

From March to Mid-June of 2021 and 2022, we photographed, and 3D scanned 83 lapwing nests. Each nest was scanned with an ASUS Zenfone AR using the Matterport Scenes app from a height of 1.2m (Shults et al., 2019). Phone 3D scanners provides a cheap and relatively easy method for capturing 3D point clouds using triangulation from an structured light time-of-flight sensor (Froehlich et al., 2017). Scans were taken from a height of 1.2 metres at a flat 90o polar (vertical) angle from the ground. Each scan taking 7 seconds to complete.  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.