The Wilson Journal of Ornithology 123(2):339-346, 2011 
GEOGRAPHIC VARIATION IN TYPE I SONGS OF BLACK-THROATED 
GRAY WARBLERS 
STEWART W. JANES' 2 AND LEE RYKER 1 
ABSTRACT.—We studied songs of Black-throated Gray Warblers (Dendroica nigrescent) in a fragmented landscape in 
southwestern Oregon and northern California where each male sings a single Type 1 song consisting of two phrases. 
Fourteen variants of Type 1 songs were distributed in a complex geographic pattern across 19,400 km 2 of the region. 
Variants differed in number of noles/syllables in the A-phrasc (range 2-5). and the B-phrase differed in both the number 
and structure of syllables. Several variants occurred in well-defined ureas and differed from neighboring songs; others 
overlapped adjacent variants or graded from one form to another across a narrow /one. Distinct variants could be identified, 
but the diversity of Type I songs and the pattern of distribution throughout the region does not describe a clear system of 
dialects. Geographic extent of the variants differed considerably; some occurred as small scattered populations occupying 
• 250 km 2 while the largest exceeded 3,000 knv. Variants in the most restricted area and having the most fragmented 
distribution had the least consistent structure among individuals both within local populations and across the range of the 
vanant. Ridges >1,000-1.200 m in elevation served as effective barriers and separated sets of similar song variants. Fire 
also likely had a role in generation of variants as reflected by multiple variants occurring in areas lacking obvious 
geographic barriers. Received # December 2(MN. Accepted 23 December 2010. 
The songs of most birds exhibit geographic 
variation. This variation may be manifested as 
dialects: songs similar in form, distinct from 
neighboring song variants, and exhibiting minimal 
spatial overlap with neighboring song variants. 
Many species of wood-warblers (Parulidae) 
sing multiple distinct songs that can be classified 
into two general song categories (Spector 1992) 
on the basis of context. Type I songs predominate 
early in the breeding season prior to pairing. Type 
II songs lend to be delivered before dawn after 
pairing, near territorial boundaries, during territo¬ 
rial contests, and often with chip-like notes. Songs 
of the two categories often differ in structure and 
are leaned form-encoded songs (Byers 1995). 
Dialects are common among second category 
songs of wood-warblers with form-encoded songs, 
bw not among first. Chestnut-sided Warblers 
<Dendroica pensylvanica). for example, exhibit 
dialects of Type II (second category) songs that 
change over a distance of several kilometers but 
s *ng similar Type I (first category) songs from 
Minnesota to Massachusetts, a distance of 
1.600 km (Byers 1996). 
The Hermit Warbler (D. occidental)!;) is tine of 
•he few wood-warblers for which dialects of Type l 
vongs have been described (Janes and Ryker 2006). 
The dialects encompass relatively large areas at 
limes exceeding 6,000 km 2 , much larger areas than 
dialects of Type 11 songs by other wood-warblers. 
Biology Department, Southern Oregon University, 
Ashland. OR y7520, USA. 
"Corresponding author; e-mail: janes@sou.edu 
The Spatial scale of Type I dialects among Hermit 
Warblers is similar to that of dialects observed in 
other species such as White-crowned Sparrows 
(Zonotrichia leucophrys) (Chilton and Lein 1996, 
Nelson and Soha 2004). 
Black-throated Gray Warblers (D. nigrescens ) 
breed in the same fragmented landscape as Hermit 
Warblers and also sing form-encoded songs 
(Morrison and Hardy 1983, Morrison 1990, Guzy 
and Lowther 1997). We investigated whether 
Black-throated Gray Warblers exhibit dialects of 
Type 1 songs and whether song differences are 
similar to those of Hermit Warblers in differen¬ 
tiation and geographic pattern and scale. 
METHODS 
Study Area .—The area encompassed 19,400 km 2 
in southern Oregon and northern California from 
the coast to the Cascade Mountains, and from the 
Klamath River watershed north to the Umpqua 
River watershed (Fig. I). The natural vegetation 
of the area is diverse including grassland, 
chaparral, oak (Quercus garryana) savanna, and 
a variety of forest types (Franklin and Dymess 
1973). Black-throated Gray Warblers tend to 
occur at lower elevations within the study area. 
They are most common in the interior valleys in 
the interface between (1) chaparral dominated by 
buekbrush (Ceanothus cuneatus), whiteleaf man- 
zanita (Arctostaphylos vicida), and poison oak 
(Toxicodendron diversiloba), (2) Oregon white 
oak (<2- garryatw) woodland, and (3) mixed 
conifer/hardwood forest dominated by Douglas- 
fir (Pseudotsuga menziesii). Pacific madrone 
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