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.