Setophaga citrina (Boddaert, 1783)
Click to enlarge
Basis for Listing
The hooded warbler is a fairly common deciduous forest inhabitant in much of the eastern United States and southeastern Ontario, Canada. It reaches its northwestern range limit in extreme eastern Iowa and southern Wisconsin. Minnesota's small breeding population of hooded warblers appears to be disjunct from the remainder of the species' range. Until recently, hooded warblers only occurred in Minnesota as a very rare, but regular, visitor, primarily during spring migration.
Adult hooded warblers have olive green upperparts, contrasting with bright yellow underparts. They also have white on the outer edges of their tails. Adult males are unmistakable, with a black hood and throat surrounding a bright yellow face. Females lack the full dark hood, typically having a dark crown and sides of the neck, and occasionally showing traces of black on the throat or upper breast. Female Wilson's warblers (Cardellina pusilla) resemble female hooded warblers, but they lack the white marking on the outer edge of their tail. Male hooded warblers have a loud, distinctive song, consisting of four to five musical, whistled notes. Each male has an individually distinctive song (Evans Ogden and Stutchbury 1994).
Hooded warblers are typically found in large tracts of mature deciduous forest with a dense, shrubby understory and shrub layer. Often the shrubby areas preferred by this species are in openings created by fallen trees. The habitat at Murphy-Hanrehan Park Reserve is characterized by mature, closed-canopy forest, with numerous small knolls and wetland potholes. Elsewhere in their U.S. range, hooded warblers commonly occupy selectively logged forests one to five years after harvesting (Evans Ogden and Stutchbury 1994; NatureServe 2011).
Biology / Life History
The main wintering habitat of the hooded warbler is on the Yucatan peninsula of Mexico. In winter habitat, individuals are strongly territorial and segregated by sex, with males most likely to be found in higher quality habitat. The hooded warbler is present on its breeding grounds from approximately May through August or September. Individuals pair up and nest in territories established by the males. Returning males usually occupy the same territory in subsequent years. Territories range from 0.5-0.75 ha (1.2-1.9 ac.) in size. Nests are built in shrubs, often at the edges of forest clearings. Females typically lay 3-4 eggs per clutch, which hatch in 12 days. The young are altricial, and fledge in approximately 8-9 days. Major food items include small spiders and insects (Evans Ogden and Stutchbury 1994).
Conservation / Management
Hooded warblers require mature deciduous forest in areas with a dense shrub layer, and are typically limited to larger tracts of forest. Their broods are often parasitized by brown-headed cowbirds. In fact, hooded warblers may be preferentially chosen as hosts, perhaps because the chipping calls of female hooded warblers makes nest construction behavior conspicuous to cowbirds. Female hooded warblers often do not eject parasitic eggs from their nest, and incubate cowbird eggs along with their own (Evans Ogden and Stutchbury 1994). Management of hooded warbler habitat to promote a dense understory while preventing fragmentation is necessary to conserve this species.
Conservation Efforts in Minnesota
The small nesting population of hooded warblers at Murphy-Hanrehan Regional Park has been closely monitored, and is largely protected from disturbance. The second known nesting site, in central Minnesota, also occurs in a protected area, although hooded warblers may no longer occur there. Bird surveys by the Minnesota Biological Survey have failed to find any additional breeding pairs of hooded warblers outside of these two sites. Hooded warblers require mature deciduous forest with a dense shrub layer. Murphy-Hanrehan Regional Park represents one of the largest blocks of forest in the Minneapolis-St. Paul metropolitan area. However, extensive tracts of apparently suitable habitat occur elsewhere in southeastern Minnesota, but remain unused by hooded warblers. It is unclear why this species seems to have only colonized two sites, and apparently has not expanded into other areas.