Common Name: Mourning
Warbler
Scientific Name:
Oporornis philadelphia
Nest Type: Cup
Nest Location: Ground,
shrubs; 0-2.5'
Clutch Size: 3-5;
avg. 3-4
Food: Insects
Foraging Guild:
Foliage and ground gleaner
The Mourning Warbler is
a common breeding species throughout eastern Canada, and south into
the north-central and northeastern United States (Peterson 1980). It
is a summer resident primarily in the wooded portions of Minnesota north
of the Twin Cities (Janssen 1987). In June of 1983 and 1984, there were
records from Brown County in the Minnesota River Valley (Janssen 1987),
and in 1989, a pair was observed feeding fledged young at Murphy-Hanrehan
Park in northeastern Scott County (C. Pearson, personal observation).
This species is a long distance migrant, wintering from southern Nicaragua
south to northern South America (Ehrlich et al. 1988). The spring migration
period extends from early May through early June with most individuals
arriving during late May. During the fall, most birds leave the state
from late August through early October (Janssen 1987).
The Mourning Warbler is
commonly found in brushy clearings or dense undergrowth of open woodlands.
It may also be encountered in roadside tangles and swampy thickets along
bog and marsh edges (Harrison 1975, Ehrlich et al. 1988). Cox (1960)
found Mourning Warblers breeding in a wide range of coniferous and deciduous
habitats with partially open canopies, and dense herb and shrub cover.
Titterington et al. (1979) recorded the highest densities of Mourning
Warblers (about 4 pair/40 acres) in the second seral stage after clearcutting
of spruce-fir forests in Maine (3-5 years after cutting). This stage
was characterized by a dense raspberry stratum and regenerating hardwoods
<2 m tall (Titterington et al. 1979).
In Minnesota, the Mourning
Warbler is one of the most abundant birds found in early successional
forests following logging or forest fire (Niemi 1977, Niemi and Probst
1990, Probst et al. 1992). In these habitats, densities of Mourning
Warblers are often 1 pair/ha or greater. Data collected in the Michigan
Breeding Bird Atlas Habitat Survey indicate a preference for wet and
mesic habitats (72%), and for young or second-growth vegetation (62%)
(Brewer et al. 1991).
The Mourning Warbler forages
in thickets or on the ground for insects and spiders (Cox 1960, Ehrlich
et al. 1988). The nest is placed on or near the ground, and is well-concealed
among dense herbaceous plants or in a tangle of briars (Bent 1953, Cox
1960, Harrison 1975). Three to five eggs are laid (Cox 1960, Harrison
1975), and apparently only one brood is raised per season.
Although the Mourning Warbler
will likely benefit from timber harvest in terms of increased habitat
and early successional vegetation, it may be susceptible to the increased
nest predation that may accompany forest fragmentation. Data collected
in the USFWS Breeding Bird Survey showed no significant trend in numbers
of Mourning Warblers recorded. Highest counts were in Ontario and the
central portion of the spruce-hardwood forest region (Robbins et al.
1986).
