SPECIES
384
BLUE-WINGED WARBLER
Vermivora pinus
The Blue-winged Warbler is usually recognized by its buzzy
"bee-buzz" songs. This attractive warbler with yellow head
and body and bluish wings is found through the southern half
of the LP and locally in the northern part of the LP. The
breeding range for the species includes most of North
America east of the Great Plains, including the northern states
and extreme southern Ontario, and the southern states as
far south as northern Georgia. Its wintering range extends
from Mexico and Central America south to Panama (AOU
1983).
HABITAT The Blue-winged Warbler breeds in open
shrubby habitats, woodland openings, edges of streams, wil
low swamps, and old fields with shrubs and small deciduous
trees. Vegetation commonly consists of aspen, willow, maple,
hawthorn, black locust, gray dogwood, and alder buckthorn,
in early stages of succession. The habitat often includes low,
dense shrubs bordered by an open grassy area (Ficken and
Ficken 1968a, 1968b, Gill and Murray 1972a, Ewert 1981).
The nest is built on the ground under a tussock of grass.
SEASONAL OCCURRENCE Blue-winged Warblers are
summer residents in Michigan. They arrive from early to mid
May. Males are most conspicuous while they sing during the
second half of May and early June, and they become more
quiet when nesting is finished in June. Nesting begins with
egg laying dates around 28 May, and the species has only one
brood in a season (Will 1986). Most individuals leave for their
wintering grounds around the middle of August (Wood 1951).
STATUS
Blue-winged Warblers are now common in the
southern third of Michigan but were not known in the state
during the middle 1800s. The first record was in Kalamazoo
in 1879; the first pair, suggesting breeding, was seen in
Wayne Co. in 1902. A Blue-winged Warbler was seen in 1896
in Ann Arbor, Washtenaw Co., but they were not regular
there until 20 years later (Barrows 1912, Wood 1951, W.
Koelz pers. comm.). As in the eastern part of their range in
North America, Blue-winged Warblers in Michigan have
expanded northward during the past 80 years and the range
ACCOUNTS
extension has coincided with a northward shift of Goldenwinged Warblers (Gill 1980).
By the 1930s Blue-wings were fairly common in south
western Michigan and throughout the southern three tiers
of counties. By the 1950s they were more common than the
Golden-winged Warbler in southwestern Michigan (Wood
1951, Berger 1958), and by the late 1960s they were more
common in southeastern Michigan (Gill and Murray 1972a,
1972b, Murray and Gill 1976). In Isabella Co., halfway up
the LP, the species appeared in 1979 and 1980 in sapling
aspen and paper birch where Golden-winged Warblers were
also seen (Ewert 1981).
The Atlas observations provide good documentation of this
warbler's present-day distribution, and are consistent with
a continuing expansion in Michigan. Blue-wings are now com
mon in much of the southern LP. Overall, they are more com
mon in the southwestern part of the state. They were found
in every township in Barry and Kalamazoo counties. In the
southeast, they breed in several areas in Livingston, Oakland,
Lapeer, St. Clair, and Tuscola counties. The northernmost
breeding, in Benzie Co., involved a hybrid "Brewster's
Warbler." The well-concealed nests are difficult to find. Most
confirmed breeding records were of adults attending young
and fledglings after they had departed the nest.
Difficulties in censusing the species include the similarity
of the songs of Blue-winged and Golden-winged warblers,
though usually the songs are distinct. Some individuals of each
species give the song of the other species (Ficken and Ficken
1968b, 1968c, 1969, Gill and Murray 1972a, 1972b). Also,
the two sometimes associate in mixed pairs, interbreed, and
produce hybrid offspring.
"Brewster's Warbler," once named as a distinct species,
is the most common form of hybrid, the male white on the
throat and belly, and the breast, wing bars, and cap bright
yellow. This hybrid was observed in 27 Atlas blocks.
"Lawrence's Warbler," the hybrid form with yellow underparts and a black throat and face pattern, is less common and
was seen in 8 Atlas blocks. Both hybrid forms were observed
throughout the range of overlap of Blue-winged and Goldenwinged warblers in the Atlas observations. One "Brewster's"
was found in Dickinson Co. in the UP, observed with a
Golden-winged Warbler.
Two color-banded male "Brewster's Warblers" survived
for four years in the E. S. George Reserve in Livingston Co.
One mated with a female Blue-winged Warbler; the other
mated with a female Golden-winged Warbler and fledged a
brood of six young. In each case the female mated with a male
"Brewster's Warbler" that sang the song of her own species,
and in each case the fledged brood were yellow in juvenile
plumage, like young Blue-winged Warblers (orig. obs.).
Hybrids may have the song of either parent species,
perhaps depending on which species was the father. Females
of both species of warblers tend to mate with a like male,
but where they both occur in southern Michigan, the inci
dence of mixed matings and hybridization is about 20% (Gill
and Murray 1972a). Playback of tape-recorded songs usually
attracts the singing male into sight (Ficken and Ficken 1969,
Gill and Murray 1972b). The species is more likely to respond
selectively to song of its own species in an area where the
two have lived together for many years (Crook 1984). Because
the song may not match the plumage identity of the singing
bird, and its mate may not be the same species as the sing
ing male, censusing efforts should include visual identifica
tion of the warbler and its mate.
Robert B. Payne
BLUE-WINGED WARBLER
BREEDING EVIDENCE
Number of townships reported
■ Possible
• Probable
■ Confirmed
REGION TOTALS
UP
NLP
SLP
0
0
37
171
TOTALS
208
16
116
132
0
4
57
61
0
57
344
401
Percentage of total townships
0.0
(of 610)
BBS Abundance
Number of birds per route
0
40
Kilometers
80
9.7
(of 590)
49.4
(of 696)
21.1
(of 1896)