and begin displaying before the predator is in sufficient proximity to locate the nest. Ground-nesting birds employ different defensive behaviors as part of their antipredator strategies because they nest where a wide range of predators have access. It has been shown that for Kentish plovers there is a positive correlation between male and female defense behaviors within pairs and that nests in which parents invested more on defense survived longer. Furthermore, if the nest is on or near the ground, the parent may be able to display more effectively; Armstrong noted the relative rarity in the literature of distraction display in arboreal-nesting species, and attributed this to the difficulty of displaying convincingly while on a branch. Nonetheless, there have been anecdotal reports of warblers, which nest arboreally, dropping to the ground to perform a distraction display when disturbed, as well as displaying along a tree branch. In addition, distraction display tends to be most adaptive when animals nest solitarily, as solitary nesters lack the opportunity for mobbing a predator or otherwise performing communal defense, although some species have been observed to display in groups. Finally, distraction display tends to be adaptive when diurnal predation by visually-stimulated predators takes place (as these predators are most likely to notice the visual display). In birds Distraction display has been most extensively studied in birds. It has been observed in many species, including passerines and non-passerines, and has been particularly well documented in the Charadriiformes. Injury-feigning, including broken-wing and impeded flight displays, is one of the more common forms of distraction. In broken-wing displays, birds that are at the nest walk away from it with wings quivering so as to appear as an easy target for a predator. Such injury-feigning displays are particularly well known in nesting waders and plovers, but also have been documented in other species, including snowy owls, the alpine accentor, and the mourning dove. Impeded flight displays additionally may suggest an injured wing, but through an airborne display. False brooding is an approach used by plovers. The bird moves away from the nest site and crouches on the ground so as to appear to be sitting at a nonexistent nest and allows the predator to approach closely before escaping. Another display seen in plovers, as well as some passerine birds, is the rodent run, in which the nesting bird ruffles its back feathers, crouches, and runs away from the predator.