Warblers are insectivorous birds which are mainly found in arboreal habitats. Some are associated with water in the form of reed-beds or tall grasses. Others are found close to streams or in woodland alongside water courses. The majority are found in tree foliage at ground, middle and canopy levels where they glean insects from leaves.

They can be split into two sub-groups:-

• Old World Warblers.
• New World Warblers.

Old World Warblers.

In the IOC listing these birds are shown in family Sylviidae but other birds known as Warblers are listed in family Cisticolidae (Cisticolas, Prinias, Apalis and related birds) and Tailorbirds whose family is uncertain. In terms of habitat and geographical location I group them as follows:-

Ground foragers.
Genus Tesia, found in Asia and Australia where they inhabit forest undergrowth on or near the ground. In Africa and Asia the Tailorbirds of genus Ortholomus are skulking birds of the forest undergrowth and scrub.

Tall grass and reed foragers.
Mainly genus Locustella in Europe. They like low level grasslands with dense, low vegetation. Tall, long grass and reed stems are favoured by Cisticolas of Africa and Prinias of Africa and Eurasia.

Marsh foragers.
Genus Acrocephalus found mainly in Europe and Africa favour marshes, reed-beds, rank vegetation and swamps. Genera Cettia and Bradypterus of Asia and Africa are secretive Warblers occupying reed-beds, dense undergrowth and lush vegetation. Cetti’s Warbler is an example of this sub-group.

Scrub and tree gleaners.
Genus Hippolais found only in Europe where their habitats range from dry, low scrub to mature, deciduous forests. Genus Phylloscopus are forest dwelling Leaf Warblers mainly occupying the canopy in Africa, Europe and Asia. Willow Warblers, Chiffchaff and Radde’s Warbler are examples here.

New World Warblers.

These birds are listed in family Parulidae and are mainly forest Warblers. Their habitats range from open woodland to deep, thick forests. Various habitats can be defined:-

Ground foragers.
The Louisiana Waterthrush walks and forages on the ground favouring streamside areas.

Riverine, woodland foragers.
In the south-west of North America Lucy’s Warbler and the Yellow Warbler are found in woodlands which border watercourses across the desert.
Low bushes and undergrowth in ravines and gorges, in areas of woodland bordering rivers and in moist swampy areas are the habitat favoured by Townsend's Warbler and the Yellow-throated Warbler.

Woodland undergrowth.
Swainson's, Hooded Warbler and the Kentucky Warbler favour the forest understory.
Mourning, Macgillivrays, and Black-throated Blue Warbler and the Yellow-breasted Chat Warbler like dense, shrubby thickets close to water. The Prarie Warbler likes shrubby areas in pine woodlands.

Woodlands with tall shrubs and small trees.
Tennessee, Bay-breasted Warblers and the Orange-crowned Warbler favour this habitat.

Bushy, forest margins or clearings.
Blue-winged Warbler favours willow swamps, overgrown fields and pastures, woodland edges and clearings. Golden-winged Warbler also likes these areas. Common Yellowthroat favours damp, brushy or marshy habitats. The Grey-crowned Yellowthroat is found in this habitat as far north as the Rio Grande.

Forests and woodland.
Black-throated Grey Warblers like oak, pine and juniper forests. Coniferous forests are favoured by Grace’s and the Pine Warbler during the breeding season. The latter species like open mature pine woodland. Yellow throated Warblers choose sycamore or pine woodlands. Wilson’s Warbler favours broad-leaf trees and shrubs like alder and willow thickets. The Nashville Warbler likes wet coniferous forests. Yellow-rumped Warbler prefers coniferous or mixed over deciduous woodland.

The Northern Parula likes swampy areas festooned with Spanish moss in oak woodlands. Chestnut-sided Warbler and the Magnolia Warbler like oak woodlands. Blackburnian Warbler likes oak woodlands where it gleans insects from the surfaces of leaves and twigs.

The Black & White Warbler forages by trunk creeping.
American Redstart is more suited to flycatching in mixed forests.
Redstarts (more correctly White-starts) favour montane regions of the neotropics.
Golden-cheeked Warbler is endemic to hillside “cedar breaks”.