The UK's breeding population of Northern Lapwing has plummeted by 59% since 1967. Agricultural changes, including the loss of mixed farming, and the intensification of grassland management, have driven the decline.
However, reserve managers are familiar with the added threat of predation, with each year's breeding success dependent in part on the number of eggs and young lost to opportunistic species such as foxes and corvids.
Northern Lapwing is a priority species at many nature reserves (Ian Bollen).
A study led by the University of Exeter has shown that lapwings can conceal their eggs by selecting nest sites based on variations in the surrounding terrain, rendering them invisible to all but the closest-passing ground predators.
By complementing the camouflage of their eggs with this 'clever' site selection, their nests are impossible for a fox to see from more than 1.5 m away.
George Hancock, lead author from the Centre for Ecology and Conservation on Exeter's Penryn Campus in Cornwall, said: "If a nest is properly concealed in this way, it doesn't matter how good a predator's vision is – they simply won't be able to see it until they are nearly on top of it.
"Nests and eggs are also camouflaged – blending in with their surroundings by matching their backgrounds colour and pattern – but it appears this is a secondary defence."
Smartphones equipped with 3D-scanning technology were used to measure the shape of lapwing nests and the surrounding ground in the project, which was funded by the Game and Wildlife Conservation Trust (GWCT) and the Natural Environment Research Council (NERC). Specialised ultraviolet cameras were also used to help test the visibility of lapwing nests to predators.
Hancock found that lapwings prefer uneven ground for their nests, selecting elevated positions which offer reduced risk of flooding while allowing them to see predators, but without being so high as to be seen themselves.
Habitat variation appears to be crucial for allowing lapwings to select nest sites with a higher chance of success, according to Hancock.
He said: "The growth of intensive agriculture has left ground-nesting birds with poorer choices of where to nest. Grazed fields provide good habitat, as long as they're not overstocked with too many grazing animals.
"New technology is allowing us to better measure how animals see and view the world."
The findings could prove invaluable in future conservation efforts, informing the management of habitats to allow lapwings to best conceal their nests from predators, working alongside direct predator control to boost breeding productivity.
Hancock, G R A, Grayshon, L, Burrell, R, Cuthill, I, Hoodless, A, Troscianko, J. 2023. Habitat geometry rather than visual acuity limits the visibility of a ground‐nesting bird's clutch to terrestrial predators. Ecology and Evolution, 2023; 13 (9) DOI: https://doi.org/10.1002/ece3.10471