Photo: Brian E. Small/Vireo

Worm-eating Warbler

Helmitheros vermivorum

A dry trilled song in the undergrowth of deciduous woods in summer announces that the Worm-eating Warbler is at home. Less colorful than most of its relatives, it is also more sluggish, foraging deliberately in the woodland understory or on the ground, probing among dead leaves with its rather long bill. Despite the name, it does not feed on earthworms; it does eat caterpillars, but no more than many other warblers.
Conservation status Has disappeared from some areas with clearing of forest. Current numbers probably stable. Will become more vulnerable to parasitism by cowbirds where forest is broken up into smaller patches.
Family Wood Warblers
Habitat Leafy wooded slopes. During breeding season, frequents dense deciduous woodlands. Prefers cool, shaded banks, sheer gullies and steep, forested slopes covered with medium-sized trees and an undergrowth of saplings and shrubs. In winter in the tropics, forages alone in dense thickets or in the forest undergrowth, usually near the ground.
A dry trilled song in the undergrowth of deciduous woods in summer announces that the Worm-eating Warbler is at home. Less colorful than most of its relatives, it is also more sluggish, foraging deliberately in the woodland understory or on the ground, probing among dead leaves with its rather long bill. Despite the name, it does not feed on earthworms; it does eat caterpillars, but no more than many other warblers.
Photo Gallery
  • adult
  • adult
Feeding Behavior

Forages mostly in trees and shrubs. Probes in curled, dead leaves for insects, and searches on bark of trunks and limbs. Forages also on the ground, walking while seeking insects on the leaf-litter.


Eggs

4-5, sometimes 3-6. White, with brown spots and blotches. Incubated by female alone, 13 days. In most areas, rarely parasitized by cowbirds, possibly because it breeds mainly in dense woods far from edges. In some areas, parasitism by cowbirds appears to be more common. Young: Fed by both parents. Leave the nest at 10 days of age. Probably 1 brood per year.


Young

Fed by both parents. Leave the nest at 10 days of age. Probably 1 brood per year.

Diet

Mostly insects. Eats smooth caterpillars, but rarely or never takes the earthworms that the name would seem to imply. Also feeds on small grasshoppers, bugs, ants, bees, walkingsticks, beetles, sawfly larvae, and spiders. Feeds nestlings on moths and grubs.


Nesting

Males defend territories by singing from perches at mid-levels or on the ground. Besides the usual insect-like trill, male also sings a musical, varied song during flight as part of courtship. Nest: Placed on ground, normally on hillside against a deciduous shrub or sapling, well concealed by dead leaves. Nest (constructed by female) is an open cup of dead leaf skeletons; lined with fungus filaments, hair moss, maple seed stems, animal hair.

Illustration © David Allen Sibley.
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Text © Kenn Kaufman, adapted from
Lives of North American Birds

Migration

Migrates mostly at night. Fall migration begins early, many moving south in August. Very rare stray in west, mostly in fall.

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Migration

Migrates mostly at night. Fall migration begins early, many moving south in August. Very rare stray in west, mostly in fall.

  • All Seasons - Common
  • All Seasons - Uncommon
  • Breeding - Common
  • Breeding - Uncommon
  • Winter - Common
  • Winter - Uncommon
  • Migration - Common
  • Migration - Uncommon
Songs and Calls
Song like that of Chipping Sparrow, but faster, buzzy, and more insect-like.
Audio © Lang Elliott, Bob McGuire, Kevin Colver, Martyn Stewart and others.
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How climate change could affect this bird's range

In the broadest and most detailed study of its kind, Audubon scientists have used hundreds of thousands of citizen-science observations and sophisticated climate models to predict how birds in the U.S. and Canada will react to climate change.

Learn more

Read more: climate.audubon.org
Wood Warblers Perching Birds

Worm-eating Warbler

The darker the color, the more favorable the climate conditions are for survival. The outlined areas represent approximate current range for each season.

More on reading these maps.

Each map is a visual guide to where a particular bird species may find the climate conditions it needs to survive in the future. We call this the bird’s “climatic range.”

The colors indicate the season in which the bird may find suitable conditions— blue for winter, yellow for summer (breeding), and green for where they overlap (indicating their presence year-round).

The darker the shaded area, the more likely it is the bird species will find suitable climate conditions to survive there.

The outline of the approximate current range for each season remains fixed in each frame, allowing you to compare how the range will expand, contract, or shift in the future.

The first frame of the animation shows where the bird can find a suitable climate today (based on data from 2000). The next three frames predict where this bird’s suitable climate may shift in the future—one frame each for 2020, 2050, and 2080.

You can play or pause the animation with the orange button in the lower left, or select an individual frame to study by clicking on its year.

The darker the color, the more favorable the climate conditions are for survival. The outlined areas represent approximate current range for each season. More on reading these maps.
Winter
Summer

Winter Range
Summer Range
Both Seasons
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