Forest fragmentation and its effects on birds

Fragmentation of forest land, whether by suburban development, highways, transmission lines, or poorly planned cutting regimes, seriously affects reproduction by the large numbers of obligate forest interior birds. Many of our warblers, vireos, thrushes, tanagers, and flycatchers are highly migratory insectivorous birds that spend more than half the year in the neotropics, but migrate north to the United States and Canada to rear their young. These tropical visitors are especially vulnerable to predation and cowbird parasitism and are unable to maintain their populations within 100-200 m of forest edge. Habitats for these declining species can be provided by managing forest lands in large blocks so as to maintain at all times extensive contiguous areas of successional stages as well as of mature forest. Avoiding scattered small cuts will also help by reducing edge, road construction, and other disturbance.