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 criterion of the IUCN Red List (that is, declining more than 30 percent in ten years or three generations). For these reasons, the species is evaluated as "least concern". None of the major subspecies is under threat, but "exsul", as noted above, is probably extinct. There is a slow population increase of common chiffchaff in the Czech Republic. The range of at least "P. c. collybita" seems to be expanding, with northward advances in Scotland, Norway and Sweden and a large population increase in Denmark. Common chiffchaff The common chiffchaff ("Phylloscopus collybita"), or simply the chiffchaff, is a common and