Scientific Name:
Oporonis agilis
Nest Type: Cup
Nest Location: Ground
(usually in sphagnum tussock)
Clutch Size: 4-5
Food: Insects
Foraging Guild:
Ground and foliage gleaner
The Connecticut Warbler
is a regular summer resident in northeastern Minnesota (Janssen 1987).
The species also breeds in northern Wisconsin and Michigan in the United
States and in regions of most Canadian provinces. Spring migration in
Minnesota peaks in late May, and fall migration occurs from mid-August
through late October (Janssen 1987). Few individuals are seen in migration
(Eckert 1983), but in Wisconsin, data from banding records and tower
kills, indicate that the species is more abundant during migration than
observation records alone suggest (Robbins 1991). The historical range
of this species in the state included areas as far south as Isanti County
(Roberts 1932). The winter range is not well known but is believed to
be in northern and central South America (Ehrlich et al. 1988).
Connecticut Warblers forage
on the ground and in low shrubs (Morse 1989), but few specifics are
known about their diet. Invertebrates in moss and leaf litter likely
make up the majority of items taken, with some seeds and fruit making
up a small percentage of the diet (Ehrlich et al. 1988).
Breeding habitat includes
mature black spruce-tamarack bogs (Roberts 1932, Erskine 1977, Hanowski
and Niemi 1991a, 1991b, Niemi and Hanowski 1992), and jack pine barrens
with a thick shrub understory (Robbins 1991). Hence, the species is
classified as associated with mature, coniferous forests. However, the
species is most abundant in mature, lowland coniferous habitats and
is uncommon to rare in other types of coniferous vegetation (e.g., Niemi
and Pfannmuller 1979, Green and Niemi 1978, Warner and Wells 1984).
Nests are built of leaves
in sphagnum moss or grass, or are simple depressions lined with fine
grasses and roots (Roberts 1932, Ehrlich et al. 1988). Clutches usually
contain 4-5 eggs, but little is known about incubation time or time
to fledging (Ehrlich et al. 1988). The Connecticut Warbler may be sensitive
to habitat fragmentation due to increases in nest predation and parasitism
that may accompany decreases in forest interior habitat (Wilcove 1985).
Management prescriptions
on bird species as poorly known as the Connecticut Warbler are speculative.
It is likely, however, that historical range reductions in Minnesota
have been due to loss of suitable nesting habitat in more southerly
portions of this species range. Maintenance of mature black spruce-tamarack
bogs is essential.
Roadside count data for
Minnesota has indicated no change in the population of the species since
1966 (Janssen 1990). However, few individuals of this species are observed
along these routes. Hence, the sample size is relatively small for detecting
a significant trend.
