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THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 123, No. 1, March 2011 
forms that present more well-marked characters in 
females than in males, variation which he termed 
heterogynism. In temporal order, the seven 
subspecies are W. p. poecilinotus (Cabanis 
1847), W. p. griseiventris (von Pelzeln 1869), W. 
p. lepidonotus (Sclater and Salvin 1880), W. p. 
vidua (Hellmayr 1905), W. p. nigrigula (Snethlage 
1914), W. p. duidae (Chapman 1923), and W. p. 
gutturalis (Todd 1927). Together they populate 
the Amazonian lowlands (Fig. 1). 
In the years since these subspecies were 
described, ornithological surveys in Amazonia 
have expanded our knowledge of their distribution 
and have produced a large number of vocal 
recordings from throughout their range. Vocal 
characters afford a relevant “yardstick” ( sensu 
Mayr and Ashlock 199!) for estimating repro¬ 
ductive isolation and species status of sympatric 
and allopatric populations of suboscine passerines 
(Isler et al. 1998, Johnson et al. 1999, Baptista and 
Kroodsma 2001, Helbig et al. 2002, Remsen 
2005). Recently obtained data provide an oppor¬ 
tunity to reevaluate the taxonomic status of 
Willisornis populations based on geographic 
relationships among plumage-defined subspecies, 
and on the extent to which vocal differences 
among these subspecies support species status. 
METHODS 
Populations were based on geographic ranges 
of currently defined subspecies with two further 
subdivisions. Vocalizations of lepidonotus were 
divided into recordings obtained below and above 
800 m elevation based on preliminary molecular 
analysis of J. M. Bates (pers. comm.). Vocaliza¬ 
tions of griseiventris were allocated to popula¬ 
tions east and west of the Rio Madeira because the 
Rio Madeira is a major barrier to gene flow in 
understory birds (Isler et al. 2007a, b; Burney and 
Brumfield 2009). 
Specimens were examined at the Louisiana 
State University Museum of Natural Science 
(LSUMZ), the Museo Paraense Emilio Goeldi 
(MPEG), the Museo de Zoologia, Universidade de 
Sao Paulo (MZUSP), and the National Museum of 
Natural History, Smithsonian Institution (USNM) 
with additional data provided by staffs of the 
American Museum of Natural History (AMNH), 
the Carnegie Museum of Natural History (CM), 
the Coleccion Ornitologica Phelps (COP), and the 
Field Museum of Natural History (FMNH). 
Measurements of bill width, depth, and length 
(at nares) and tarsus, tail, and wing chord were 
taken with MAX-CAL electronic digital calipers, 
which were also used to measure the length of the 
white interscapular patch at the center of the back. 
Colors were recorded by comparison with Mun- 
sell Soil Color Charts (Kollmorgan Instruments 
Corp., New Windsor, NY, USA), and English 
color names used in verbal plumage descriptions 
were adapted from these charts. We developed a 
locality-based map (Fig. 1) of the geographic 
distribution of each subspecies based on sites 
listed in museum inventories, sites referenced in 
the literature, and sites of vocal recordings. 
Tape and digital recordings of vocalizations 
were compiled from our own inventories, from 
unarchived contributions of other individuals, and 
from the Macaulay Library (ML, Cornell Labo¬ 
ratory of Ornithology, Ithaca, NY, USA). We 
examined 358 recordings (Appendix). We re¬ 
viewed the documentation of recordings to 
identify the number and gender of individuals 
vocalizing. RAVEN, Version 1.3 (Bioacoustics 
Research Program, Cornell Laboratory of Orni¬ 
thology, Ithaca, NY, USA) was used to make a 
spectrogram of every vocalization type delivered 
by each individual on every recording. All clearly 
delineated spectrograms were examined visually 
for characters (e.g., note shape) that might 
distinguish a population. Spectrograms shown in 
figures were selected to express typical measure¬ 
ments (e.g., the mean number of notes in 
loudsongs) and were made by exporting RAVEN 
files into CANVAS, Version 9.0.4 (ACD systems, 
Victoria, BC, Canada). 
Vocal characteristics obtained for loudsongs 
were: (1) number of notes, (2) duration, (3) pace, 
(4) change of pace, (5) note shape, (6) change in 
note shape, (7) note length, (8) change in note 
length, (9) interval length, (10) change in interval 
length, (11) frequency (nadir, peak, and max), and 
(12) change in frequency. The nadir is the lowest 
point in the tracing of a note; peak the highest 
point; and maximum frequency is measured at the 
point of highest intensity in the note. Measure¬ 
ments were taken of the initial, central (in time), 
and terminal notes and their associated intervals. 
Characteristics obtained for calls were fewer as 
they contained fewer notes. We required pairs of 
measurements expressing diagnostic characters to 
have correlation coefficients <0.80 given the 
possibility that some characters might be linked 
by common ancestry. 
Quantitative measures were obtained from 
spectrograms projected on a 43-cm screen using 
