A new species of flycatcher in the Tolmomyias assimilis radiation from the lower Sucunduri-Tapajós interfluvium in central Amazonian Brazil heralds a new chapter in Amazonian biogeography

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ORIGINAL SCIENTIFIC DESCRIPTIONS 297
Holotype.— MZUSP 86976, adult female from Brazil: Amazo-
nas; left bank rio Parauri about 6 km above cachoeira Tambor
(05°04’02’’S/58°02’40’’W) at about 70 m elevation; collected
22 July 2009 by Fabio Schunck and Marco Antonio Rêgo,
prepared by Paulo César Balduíno. Voice recorded by Bret M.
Whitney, original numbers BMW-7236 and 7237; Macaulay Li-
brary of Natural Sounds (ML) 169979. Pectoral muscle tissue
preserved in approximately 96% alcohol: MZUSP 86976,  eld
number 306.
Diagnosis: Morphology.— Distinguished from neighboring T.
a. assimilis, T. a. calamae, and T. a. paraensis by notably darker
and more uniformly leaden gray crown and slightly darker green
back. Voice.— Distinguished in the  eld and in spectrographic
analysis by the widely modulated structure of the two or three
loudest (most clearly audible) notes in the song resulting in a
distinctive “washboard” quality to these notes strikingly differ-
ent from all other taxa (see Vocalizations, below).
Distribution.— Central Amazonian Brazil from the right bank
of the Rio Canumã and Rio Sucunduri in Amazonas east to the
left bank of the lower Rio Tapajós in Pará south to approximate-
ly 05°40’S (Fig. 1; see Range delimitation and Relationships,
below).
Description of holotype.— See color illustration and Figure 2 (paratype
MZUSP 86974). Capitalized color designations (corresponding number in paren-
theses) from Smithe (1975). Alphanumeric color designation of the crown deter-
A new species of fl ycatcher in the Tolmomyias assimilis radiation from the
lower Sucunduri-Tapajós interfl uvium in central Amazonian Brazil heralds
a new chapter in Amazonian biogeography
Bret M. Whitney1, Fabio Schunck2, Marco Antonio Rêgo2, and Luís Fábio Silveira2
In July, 1995, BMW and Sally Conyne departed by boat from Santarém, Pará to travel up the Rio Tapajós to make tape-recordings of
a number of species of birds at their type localities. They anchored at the old, left-bank town of Boím on 16 July, and made their way
into tall terra  rme forest about 25 km west of the river via a recently opened logging road. Over the course of work at this site and a
week or so later, above Itaituba at the important Snethlage locality “Vila Braga,” BMW heard and recorded a distinctive song from a
canopy  ycatcher that he recognized as an undescribed, species-level representative of the widespread Tolmomyias3 assimilis (Yellow-
margined Flycatcher) complex based on parallels in its vocalizations and behavior and the biogeography of the group. He made further
recordings of the bird near the town of Maués in the state of Amazonas in July, 2002, and organized a collecting expedition to that area
through the Museum of Zoology of the University of São Paulo (MZUSP) in July, 2008. Several specimens of the new Tolmomyias were
voice-recorded and collected on that expedition, but it was decided to wait to describe the species until its western range limit could be
determined, which BMW hypothesized to be the right bank of the Rio Canumã/Sucunduri, where turnover to nominate T. assimilis was
expected to occur. A week of solo  eldwork on the lower Canumã and Sucunduri in July, 2010, con rmed that these rivers mark the
longitudinal limits of the two Tolmomyias species as well as many other species-pairs of birds under study. In July-August, 2012, BMW
directed a joint  eld expedition of the MZUSP and the Louisiana State University Museum of Natural Science (LSUMNS), largely
funded by The National Geographic Society, to that region that resulted in collection of an additional specimen of the new  ycatcher
and samples of many other common birds.
Most importantly, however, that expedition, through the description of this new species, introduces two previously undescribed avian
distribution patterns crucial to interpreting paleohistorical determinants of Amazonian biogeography in general: 1) the Rio Canumã/
Sucunduri has been the most in uential barrier to population expansion, thus directing speciation dynamics, across the entire Madeira-
Tapajós inter uvium; and 2) there exists a pervasive pattern of replacements and drop-outs among named and unnamed taxa along a
broad latitudinal and ecological gradient independent of any rivers. Focused study of both of these patterns and the processes that gave
rise to them together with documentation of genetic introgression levels among numerous populations of birds across the Madeira-
Tapajós inter uvium are the subjects of ongoing research to be illuminated in detail in future publications. For the present, to call par-
ticular attention to the seminal role of the Rio Sucunduri, we propose that this unnamed Tolmomyias  ycatcher be henceforth known as:
Tolmomyias sucunduri
Sucunduri Yellow-margined Flycatcher
Bico-chato-do-sucunduri (Portuguese)
1 Louisiana State University, Department of Biological Sciences, Museum of Natural Science, 119 Foster Hall, Baton Rouge, Louisiana 70803, USA. (ictinia@earthlink.net)
2 Seção de Aves, Museu de Zoologia da Universidade de São Paulo (MZUSP), Avenida Nazaré 481, Ipiranga, São Paulo, SP, Brazil CEP 04263-000.
3 Genus Tolmomyias 9: 338.

HANDBOOK OF THE BIRDS OF THE WORLD
298
Figure 1.
Geographic distribution of
Tolmomyias sucunduri and
some other members of the
T. assimilis complex in central
Amazonian Brazil. Red dots =
T. sucunduri. Red star = type
locality of T. sucunduri near
Maués, Amazonas, Brazil.
Letters adjacent to red locality
dots provide documentation: S =
specimen; V = vocal recording.
Black dots = other members
of the T. assimilis complex
represented by specimens
voice-recorded before collection
(see SI for a list with specimen
numbers; we have many other
localities represented by either
specimens or recordings).
Black star = type locality of
T. assimilis assimilis. White star
= type locality of T. assimilis
calamae. Black triangle =
postulated hybrid or intergrade
between T. sucunduri and T. a.
assimilis/calamae, specimen
voice-recorded before
collection. Black lines mark the
boundaries of Brazilian states
as indicated by their official
abbreviations: AM = Amazonas;
RO = Rondônia; MT = Mato
Grosso. The federal highway
BR-230 (“Transamazônica”) is
shown in white.
mined through direct comparison with Munsell soil color charts (1994); the de-
scription in quotation marks is the chart designation. Plumage fresh and unworn,
no wing molt (but P10 missing on left side), rectrices not fully grown on left side;
skull ossication not recorded. Numerous long (some exceeding 10 mm) black
rictal bristles at base of bill around commisure and over nares. Crown from base
of bill through nuchal region uniform "dark bluish gray" (nearest chart 2 for Gley
4/5PB), some feather edges of nape tinged slightly olive contrasting notably with
the uniform Greenish Olive (color 49) upperparts. Lores and tiny feathers above
base of bill whitish. Visage plain, lacking any areas of strong contrast, dark or light,
around the eyes or auriculars but photos of the bird at the time of collection (as in
Fig. 2) show a pale eyering concentrated along the upper edge of the orbit. Lower
facial region, chin and upper throat dull whitish contrasting moderately with the
gray crown and blending posteriorly toward yellowish, picking up a weak olive
tinge through the breast. Sides and anks yellowish olive becoming clear yellow
(brighter than Sulphur Yellow 157) on the belly and undertail coverts. Upperwing
coverts black with pale markings as follows: lesser and median coverts with an
Olive Green (aux. 47) spot on distal web at feather tip; greater coverts with well-
dened and more contrasting yellow (near Sulphur Yellow 157) margins to distal
webs extending to feather vane. Primaries 9 and 8 are of equal length and longest,
about 1 mm longer than P7 which is about 2 mm longer than P6; P10 is about 2 mm
longer than P4. Distal margins of primaries and, especially, secondaries conspicu-
ously fringed same yellow as edging on upperwing coverts and contrasting inside
the dark primary stack. Anterior edge of primary stack marked by an approxi-
mately 7-mm long, pale wedge formed by conspicuous, white distal margins near
the bases of P7 and P6, with that on P5 slightly shorter, and only very short and
fainter margins on P8 and P4. This pale wedge contrasts sharply with a cotermin-
ous, similarly sized, deep black triangle formed by the unmarked blackish primary
coverts. Alula dull blackish, tiny feathers at bend of wing dull yellowish white.
Underwing coverts clear, pale yellow becoming slightly duskier at the wrist. Tail
narrowly fringed with Olive Green (aux. 47) and not contrasting with upperparts.
Soft parts in life: iris clear light brown, maxilla black, mandible gray, legs dark
gray. Standard measurements: total length (just before specimen preparation)
149 mm; bill (culmen from base at skull) 13.1 mm; bill from anterior edge of nares
7.4 mm; bill width at anterior edge of nares 4.3 mm; wing (chord) 63.2 mm; tail
55.8 mm (somewhat short of fully grown?); tarsus 16.8 mm; mass 14.5 g.
Etymology.— The name refers to the Rio Sucunduri which
marks the new species’ western range limit; pronunciation of
the river name is soo-coon-doo-REE, with the accent on the -
nal syllable. The species-group name is a non-Latinized noun in
the nominative singular case. The English name unambiguously
allocates the new species to the “yellow-margined ycatcher”
complex.
REMARKS
Type series.— The following eight specimens are the paratypes
of Tolmomyias sucunduri: MZUSP 86974, 86975, 86977, 86980,
86981 male, female, male, sex unknown, and sex unknown,
respectively (AM, Maués, left bank rio Parauri); 86978 male

ORIGINAL SCIENTIFIC DESCRIPTIONS 299
(AM, Maués, right bank rio Parauri); 94841 male with spread
wing (AM, right bank lower rio Canumã); and Museu Paraense
Emílio Goldi (MPEG) 72373 male (PA; Municipality Santarém
[left bank rio Tapajós], RESEX Tapajós-Arapiuns). Among
them, there is slight variation in the amount of olive wash in the
hindcrown. Unlike the rest of the type series, the holotype shows
almost no indication of darker centers to crown feathers, these
instead being almost uniformly "dark bluish gray".
Ecology and behavior.— Prior to the discovery of Tolmomyias
sucunduri at Boím in 1995, the assimilis species-group was
known on the west bank of the Tapajós from a single female
collected in 1917 by Snethlage at Vila Braga (Oren and Parker
1997). The undescribed species had escaped collection and had
been overlooked in more recent surveys, no doubt, because it
inhabits the canopy of tall forest and its voice is so markedly
different from other members of the complex as to be “unrec-
ognizable.” Tolmomyias sucunduri is an inveterate member of
canopy mixed-species foraging ocks comprising mostly other
insectivores and usually some frugivores and nectarivores. It al-
most always accompanies ocks in pairs, the members of which
are often several meters apart and mostly just inside the periph-
ery of treecrowns, rarely descending below the subcanopy. The
broad, at bill is used as a scoop to take mostly small arthropod
prey in short-range (less than about 1 m) sally-strikes or upward-
directed hopping motions to the undersides of live leaves, and
birds frequently sit still and peer around for a minute or more.
In all these respects, T. sucunduri behaves like the other mem-
bers of the T. assimilis complex (BMW pers. obs.). Stomach
contents of 9 individuals were entirely insects, with Coleoptera,
Hymenoptera, and Hemiptera in almost all of them (see SI for a
more detailed listing by Order and Family).
Vocalizations.— The primary song of Amazonian members
of the Tolmomyias assimilis complex, delivered irregularly
throughout the day, may be characterized as a simple series of,
usually, three or four notes or syllables (sometimes up to six are
delivered; there is much intra-individual variation; Fig. 4). The
song increases in amplitude through the rst two notes, which
are typically shorter than subsequent notes and with greater in-
ter-note interval than subsequent ones, which are both uniformly
louder and longer, often the only notes of the song clearly audi-
ble from the ground. Both sexes sing, with female songs slightly
"thinner" and higher-pitched than males'. An evenly paced call-
series of (usually) 3-7 loud, sharp "chip" notes is also frequently
given by all taxa, either preceding the song or by itself (Fig.
4D, F), but this call-series appears to be given less often by T.
sucunduri.
The louder, longer notes of songs of all Amazonian Tolmo-
myias in the assimilis complex possess a harsh or "snarling"
quality that sets them apart from other members of the genus.
Our sample of 13 individual Tolmomyias sucunduri consist-
ently shows the widely modulated or "washboard" quality of
these notes that is diagnostic of the species and is never even
approached by other taxa (Fig. 4A, B; interested readers should
listen to the selection of recordings available on the Internet Bird
Collection (IBC) website for a clear understanding of distinc-
tions through inter-taxon comparison). South of approximately
05°40’S, however, this distinctive vocalization loses its identity,
apparently due to hybridization with T. assimilis/calamae (Figs.
4C, E, F) because songs of birds in that area not only sound
intermediate to us, but also show variation far outside the norm
for any taxon in the complex such that no two individuals sound
quite the same.
Range delimitation and Relationships.— Although we have no
phylogenetic analysis of even a limited part of the Tolmomyias
assimilis complex for this publication, we are completely con-
dent that T. sucunduri is an integral member of this species-
group. In the distribution of the complex, the Madeira-Tapajós
interuvium is a particularly complicated region. Nominate T. a.
assimilis, from Borba on the right bank of the lower Rio Madeira,
together with T. a. calamae from farther upriver also on the right
bank, occupy the region west of the Rio Canumã/Sucunduri, and
are replaced east of these rivers by T. sucunduri; this pattern is
paralleled by taxa in the Willisornis poecilinotus (Scale-backed
Antbird) complex (Isler and Whitney 2011). Judging from the
geographic spread of vocal types, the Madeiran population(s)
passes the Sucunduri in the narrow headwaters of the river, some
400 km to the east, and we further postulate that it has pushed
northward through the restricted, cone-shaped region between
the upper Sucunduri and the Rio Tapajós to reach approximately
05°45’S, where these birds have achieved contact, we think
probably secondary contact, with the Tapajós representative of
the radiation, which is T. sucunduri. At roughly this latitude,
there appears to be a gradient of hybridization at least 30 km
wide, as judged by the prevalence of hybrid-type vocalizations
there (collected specimens represented by black triangles in Fig.
1), and we expect that genetic introgression will prove to be con-
siderably more pervasive east of the Sucunduri. Our hypotheses
regarding the origin and dynamics of this contact zone, which is
just as clearly marked for some other species-pairs of birds and
also mirrored by numerous north-south drop-outs of named and
unnamed taxa (BMW, unpublished data), are under development
and research is ongoing. Collections of voice-recorded individu-
als in the Tolmomyias assimilis complex are steadily mounting
(black dots in Fig. 1 provide a partial view of samples currently
accumulated from the Madeira-Tapajós interuvium) and will
eventually permit a distribution-wide, concerted-data-set assess-
ment of relationships and taxonomic limits in the remarkably
widespread Tolmomyias assimilis radiation.
Conservation.— Tolmomyias sucunduri appears to be common
throughout its range and is not currently threatened.
Acknowledgments.— We are especially appreciative of our
colleagues Thiago V. Costa, Glaucia C. Del Rio, Mike Har-
vey, Glenn Seeholzer, and Ryan Terrill who helped us secure
important specimens of Tolmomyias ycatchers along the Rio
Canumã/Sucunduri in July and August 2011. The joint MZUSP/
LSUMNS 2012 research expedition to this region was funded in
part by the LSU Museum of Natural Science and the LSU De-
partment of Biological Sciences, and we are especially grateful
for a generous grant to Robb Brumeld from the National Geo-
graphic Society (9136-12). Thanks to the Fundação de Amparo
à Pesquisa no Estado de São Paulo (FAPESP) and the Conselho
Figure 2.
A paratype of Tolmomyias
sucunduri (MZUSP 86974)
from near the type locality, on
the left bank of the Rio Parauri
above Maués, Amazonas, Brazil.
Facial markings show better in
this photo than in the prepared
specimen. Audio and video
recordings were made by Bret
Whitney and photos by Fabio
Schunck, including this one, on
20 July 2009 (see SI).

H
6.05.0 7.0 8.0
G
2
4
0
0 2.01.0 3.0 4.0
6
A
2
4
0
0 2.01.0 3.0 4.0
6B
6.05.0 7.0 8.0
C
2
4
0
0 2.01.0 3.0 4.0
6D
6.05.0 7.0 8.0
E
2
4
0
0 2.01.0 3.0 4.0
6F
6.05.0 7.0 8.0
Frequency (kHz)
Time (seconds)
HANDBOOK OF THE BIRDS OF THE WORLD
300
Figure 3.
Spectrograms of typical
vocalizations of Tolmomyias
sucunduri in comparison to
homologous vocalizations of
some other members of the
Tolmomyias assimilis complex
in central Amazonian Brazil.
(A) One song of T. sucunduri
(paratype MZUSP 86974;
recording BMW-7387); (B)
Another individual of T.
sucunduri (AM; right bank Rio
Sucunduri at Igarapé Biribá, 16
July 2010; recording BMW-
10050); (C) One song of T.
assimilis assimilis from the
type locality (AM; right bank Rio
Madeira near Borba, 19 October
1993; MPEG 53182, Whitney
recording); (D) Typical call series
of T. assimilis assimilis, which
is shared by other members
of the assimilis complex (AM;
right bank Rio Madeira near
Borba, 19 October 1993; MPEG
53183, Whitney recording); (E)
One song of T. assimilis calamae
from the type locality (RO; right
bank Rio Machado/Ji-Paraná
above Palmeiras, 25 June 2002;
Whitney recording); (F) Another
song of T. assimilis calamae
(MT; left bank Rio Claro at
“Pousada Jardim d’Amazônia”,
17 June 2010; recording
BMW-9365); (G) song of T.
assimilis (currently considered
subspecies assimilis) from
west of the Rio Madeira (AM;
left bank Rio Madeira about 50
km south Humaitá; 12 August
2009; MZUSP 86239, recording
BMW-7760); (H) song of T.
assimilis (currently considered
subspecies paraensis) from
east of the Rio Tapajós (PA; right
bank Rio Teles Pires, left bank
lower Rio São Benedito, 19 June
1999; MPEG 54725, Whitney
recording).
Nacional de Desenvolvimento Cientíco e Tecnológico (CNPq)
for the concession of grants (Evolução da Fauna de Vertebrados
Terrestres Brasileiros do Cretáceo ao Presente: Paleontologia e
Filogenia, CNPq 565046/2010-1), fellowships (LFS), and for
the authorization for collecting and Research by Foreigners, and
also to the Instituto Brasileiro do Meio Ambiente e dos Recursos
Naturais Renováveis (IBAMA – SISBIO) for collecting permits.
We are grateful to NASA for free and open access to the MODIS
(EOSDIS) satellite imagery used to produce the map image. Al-
exandre Aleixo of the MPEG generously provided BMW with a
copy of his recording of the new species and he and colleagues
at MPEG managed to start a DNA-based phylogenetic analysis
that will surely help gure out what is/has been going on in the
evolutionary process of this group of birds. Fátima Lima for-
warded to us information on several specimens under her care at
the MPEG. Gabriel Bif of the Entomology Department of the
MZUSP graciously helped us by identifying arthropod stomach
contents. Phyllis Isler kindly prepared the spectrograms. Rich-
ard Banks and Thomas Schulenberg provided helpful comments
on an earlier draft of the manuscript. Hilary Burn painted the
gure of T. sucunduri that accompanies this description.
Literature Cited
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Oren, D. and T. A. Parker, III (1997). Avifauna of the Tapajós National
Park and vicinity, Amazonian Brazil. Ornithological Monographs
48: 493–525.
Smithe, F. B. (1975). Naturalist’s color guide. American Museum of
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