Scientific Name: Dendroica magnolia
Nest Type: Cup
Nest Location: Coniferous trees, shrubs; 1-35', avg. 1-10'
Clutch Size: 3-5; avg. 4
Food: Insects
Foraging Guild: Hover glean, bark gleaner
Magnolia Warblers breed from southern Canada south to Minnesota and Wisconsin
in the west and New Jersey and Massachusetts in the east (Terres 1987). In Minnesota,
Magnolia Warblers are regular summer residents in the northeastern and north-central
regions of the state. The species breeds south to Crow Wing and Mille Lacs Lake counties
and west to Roseau County (Roberts 1932, Janssen 1987). Magnolia Warblers begin
arriving in Minnesota in early to mid May. They begin to leave the state in mid August and
this migration may continue into early October. During the beginning of this migration, they
may be found in tamarack swamps or upland forests (Roberts 1932). By mid October, all
Magnolia Warblers have left for their wintering grounds in the Caribbean, Central America,
and the southern United States (Terres 1987, Ehrlich et al. 1988).
Magnolia Warblers are likely most abundant in northeastern Minnesota where they
primarily are found in the intermediate stages of coniferous forest regeneration and in some
black spruce bogs or white cedar lowlands (Green and Niemi 1978, Niemi and Pfannmuller
1979). They also breed in fir-spruce-hardwood habitats, but in lower densities than those
in pure coniferous forests (Martin 1960). Based on its high association with coniferous tree
species, the Magnolia Warbler was classified as dependent on coniferous forests.
Young conifer transition communities with conifer trees from 5 to 10 meters high are
the primary breeding habitat for this species (Green and Niemi 1978, Brewer et al. 1991).
As these trees become older, their lower branches begin to coalesce and the species,
which forages on the outer branches of the conifers, are forced to higher positions on the
trees. Hall (1984) documented a decline in population of Magnolia Warblers from 19
males/15 acres in 20 year old spruce to 2 males/15 acres in 60 year old spruce over a 40
year period of succession.
Nests are constructed in small evergreens, usually 1-2 meters above the ground,
and well hidden (Roberts 1932, Ehrlich et al. 1988). Twigs, grasses, pine needles, and
spider webs are used in nest construction, and are lined with hair, grasses, and fine, black
rootlets. Four eggs are usually laid, although 3-6 are possible, and are incubated for 11-13
days (Roberts 1932, Ehrlich et al. 1988).
Magnolia Warblers are primarily insectivorous, feeding on spiders, caterpillars, and
other insects. A small amount of fruit may also be included in their diet (Roberts 1932,
Ehrlich et al. 1988).
Although the species was not commonly found on the Breeding Bird roadside
counts, Janssen (1990) reported an increasing proportion of routes that the species was
observed on over the past 23 years. Similarly, Sauer and Droege (1992) report a slight
(2%) annual increase in the species over the past 23 years in the eastern United States.
Increased forest harvesting and management will affect this species if the proportion
of intermediately aged conifer habitat is not allowed to develop. In Minnesota, this species
primarily needs spruce and fir trees 3-10 meters in height and where these trees are
relatively dense.
