Sitting silently and motionless on their nest, adult nightjars are almost invisible. They are only detectable when they flush, sometimes also performing a "broken-wing" display in an attempt to distract the threat from their nest. This display is used as a final resort when predators get dangerously close (within 10 m).
The success of their camouflage is due to the patterning and colour of their plumage. Their feathers seem to be coloured to match their background and patterned to break up their outline, helping them to fade into the scene.
These birds are ideal for our work because they nest on the ground and allow us to get close enough to take photographs.