Gleaning (birds) World flycatchers, Tyrant flycatchers, babblers, Old World warblers, New World warblers, Vireos and some hummingbirds and cuckoos. Many birds make use of multiple feeding strategies, depending on the availability of different sources of food and opportunities of the moment. Foliage gleaning, the strategy of gleaning over the leaves and branches of trees and shrubs, can involve a variety of styles and maneuvers. Some birds, such as the common chiffchaff of Eurasia and the Wilson's warbler of North America, feed actively and appear energetic. Some will even hover in the air near a leaf or twig while gleaning from it; this
Common chiffchaff the adults are hunted by birds of prey, particularly the sparrowhawk. Small birds are also at the mercy of the weather, particularly when migrating, but also on the breeding and wintering grounds. The common chiffchaff is occasionally a host of brood parasitic cuckoos, including the common and Horsfield's cuckoos, but it recognises and rejects non-mimetic eggs and is therefore only rarely successfully brood-parasitised. Like other passerine birds, the common chiffchaff can also acquire intestinal nematode parasites and external ticks. The main effect of humans on this species is indirect, through woodland clearance which affects the habitat, predation by cats, and