Worm-eating Warbler (Helmitheros vermivorus)

Status: State Endangered (1989).

Occurrence: Rare spring migrant south and east; accidental fall migrant. Rare summer resident southwest. Nests very rarely in southern Wisconsin. Most sightings occur in April and May. Breeding populations are known only from the Baraboo Hills, Sauk County, and Wyalusing State Park in Grant County. A map outlining Pre-1977 and 1997 to Present Distribution is available.

Aid to ID: Bold, dark stripes on a buffy-orange head are distinctive. Back and wings are olive-brown; breast is a rich buffy color.

Habitat: Prefer to nest on well drained, steep sloped hillsides within ravines and large tracts of southern forest.

Food Habits: Diet consists mainly of caterpillars and other larvae, weevils, beetles, other bugs, and some spiders.

Natural History:

Breeding: Clutch size: usually 4-5 white eggs speckled with brown; laid from May to June, typically late May. Incubation: 13 days, by female. Young fledge 10 days after hatching.
Nest: Cups of dead leaves, lined with moss, hair, or the stems of maple seeds. Nests are well hidden on the ground, often under a shrub or sapling.

Management Considerations: Breeding in Wisconsin was confirmed in 1984 when M. S. Peterson discovered an active nest in the Baraboo Hills. This species is extremely rare in Wisconsin and was probably just as rare a century ago. Nests are usually located on the ground and are threatened by predation from mice, squirrels, dogs, skunks, fox, raccoons, and snakes. The extremely local distribution of breeding populations and the species' sensitivity to forest fragmentation are causes for rarity and concern. Preservation of large blocks of mature decidous forest in the Baraboo Hills and along the Mississippi and Wisconsin rivers will aid conservation efforts.