Scientific Name: Dendroica pensylvanica
Nest Type: Cup
Nest Location: Shrubs; 1-3'
Clutch Size: 3-5; avg. 4
Food: Insects, berries
Foraging Guild: Foliage gleaner, hawks, hover and gleans
The Chestnut-sided Warbler breeds from central Canada south to central North
Dakota and eastern Nebraska. The species occurs eastward to the Atlantic coast reaching
as far south as South Carolina and Georgia (Terres 1987). In Minnesota, Chestnut-sided
Warblers are common migrants and regular summer residents. They are most common in
the northern regions of the state, extending as far southward as Anoka, Stearns, and
Douglas Counties (Janssen 1987). This range has receded over the past sixty years; in
1932 Roberts reported the species to breed throughout the state (Roberts 1932).
Chestnut-sided Warblers begin returning to Minnesota in early May from their
wintering grounds in southern Central America, (Ehrlich et al. 1988), and continue arriving
into late May (Roberts 1932). These wintering grounds are geographically restricted and
the species is intolerant of disturbed habitats within this range (Finch 1991).
Chestnut-sided Warblers breed primarily in open vegetation recently disturbed by
fire or logging activities. These warblers may reach their highest densities, up to 190 pairs
per km2, in clearcuts (Freedman et al. 1981). They may also respond favorably to cottage
developments which revert the surrounding vegetation to an earlier successional stage
(Clark and Euler 1984). Chestnut-sided Warblers breed in early-successional deciduous
and coniferous communities with trees 3-30 ft high, usually associated with a dense shrub
understory. Highest densities are associated with the earliest stages of forest succession
(Green and Niemi 1978).
Data from northern Minnesota, show the species to be most common in early
successional forests, primarily deciduous in composition, with a canopy of approximately
15 feet (Niemi 1977, Niemi and Pfannmuller 1979, Niemi and Hanowski 1984, Hanowski
and Niemi 1991a, 1991b, Probst et al. 1992). Nests are usually built in saplings or low
bushes, only a few feet from the ground and often in the fork of a branch. Three to five
eggs are laid and incubated for 10-11 days. As with other open cup nesters, Chestnut-sided Warblers are frequently parasitized by Brown-headed Cowbirds (Molothrus ater)
(Roberts 1932).
Chestnut-sided Warblers are primarily insectivorous, however they will eat berries
when insects are scarce (Ehrlich et al. 1988).
In Minnesota, the species has not exhibited a change in population according to the
Breeding Bird Survey roadside counts over the past 23 years (Janssen 1990). However,
Sauer and Droege (1992) detected a short-term (1978-1988) decrease in the population
based on 584 roadside counts within the United States and Canada.
Timber harvesting opens forested areas and, therefore, creates suitable habitat for
this species. Moreover, short term rotations will likely increase habitats in earlier stages.
Hence, increased forest harvesting and management would likely be beneficial to this
species.
