Setophaga citrina (Boddaert, 1783)
Basis for Listing
The Hooded Warbler (Setophaga citrina) 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, southern Wisconsin, and southeastern Minnesota. Once considered a rare but regular migrant, mostly in spring, the species has been increasingly observed in Minnesota since the beginning of the twenty-first century and now likely breeds in at least five counties (St. Paul-Baldwin Plains and Moraines, Anoka Sand Plain, and Big Woods subsections). This increase in observations mirrors an annual population increase of 1.7% across North America from 1993 to 2015 documented by the USGS Breeding Bird Survey (Sauer et al. 2017).
Adult Hooded Warblers have olive green upperparts, contrasting with bright yellow underparts. They also have white on the outer edges of their tails, which they often flair out. 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) may resemble female Hooded Warblers, but they lack the white outer tail feathers. Male Hooded Warblers have a loud, distinctive song, consisting of four to five musical whistled notes. Each male has an individually distinctive song (Chiver et al. 2020).
Hooded Warblers are typically found in large tracts of mature mesic hardwood 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, and recent research shows that they can also occupy smaller forest fragments near larger extensive forests (Chiver et al. 2020; NatureServe 2020).
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 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 (Chiver et al. 2020).
Conservation / Management
Hooded Warblers require mature mesic hardwood forest in areas with a dense shrub layer and are typically limited to larger tracts of forest. Management of Hooded Warbler habitat to promote a dense understory while preventing fragmentation is necessary to conserve this species. Although the main cause of nestling mortality is predation, Hooded Warbler broods are often parasitized by Brown-headed Cowbirds (Chiver et al. 2020). 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 (Chiver et al. 2020).
Conservation Efforts in Minnesota
The small nesting population of Hooded Warblers at Murphy-Hanrehan Park Reserve has been closely monitored and is largely protected from disturbance. Murphy-Hanrehan Park Reserve 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.
There appears to be a rather unfortunate association between the breeding locations of Hooded Warblers in Minnesota and the abundance of common buckthorn (Rhamnus cathartica). As the warblers require dense, shrubby understories in deciduous forests in southern Minnesota, this shrub layer has been extensively and increasingly invaded by buckthorn to the detriment of native forest shrubs and regenerating trees. Buckthorn removal, while intended to benefit the forest, may have the unintended consequence of rendering the habitat unsuitable for nesting Hooded Warblers, at least for several years, until the shrub layer becomes repopulated.
Bob Dunlap (MNDNR), 2022
(Note: all content ©MNDNR)
References and Additional Information
Evans Ogden, L. J., and B. J. Stutchbury. 1994. Hooded Warbler (Wilsonia citrine). Number 110 in A. Poole and F. Gill, editors. The birds of North America. The Birds of North America, Inc., Philadelphia, Pennsylvania.
Fall, B. A. 1985. First Minnesota breeding record of the Hooded Warbler. The Loon 57:9-11.
NatureServe. 2011. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1. NatureServe, Arlington, Virginia.