Table Of ContentThe Wilson Journal ofOrnithology 119(3);439^49, 2007
AVIAN BIOGEOGRAPHY OF AMAZONIAN FLOODED FORESTS IN
THE RIO BRANCO BASIN, BRAZIL
LUCIANO NICOLAS NAKA,'''^ MARIO COHN-HAFT,' ANDREW WHITTAKER,^
JUAN MAZAR BARNETT, AND MARCELA DE FATIMA TORRES'
^
—
ABSTRACT. Flooded forests represent an important part ofAmazonian diversity, yet the distribution, ecol-
ogy, and evolutionary history of the avifauna of these forests have received little attention. We conducted
ornithological surveys in the Rio Branco Basin, which isentirely in the Brazilian State ofRoraima. Inthispaper,
we discuss the presence of 20 bird species recorded along the lower Rio Branco, 16 of which represent new
records for the State ofRoraima and the entire Rio Branco Basin. Among our most interesting records are four
species ofwhite-waterriver specialists (Synallaxispropinqua, Stigmatura napensis, Serpophaga hypoleuca, and
Conirostrum bicolor) that have populations on the lower Rio Branco, isolated from other Amazonian white-
water river systems by the black waters of the Rio Negro where they do not occur. We also discovered new
localities for the endemic and endangered Rio Branco Antbird (Cercomacra carbonaria), doubling the size of
its known range. We discuss the implications ofthese records in a biogeographic perspective for better under-
standing the distributional patterns ofthe flooded-forestavifaunain Amazonia. Received11 May2006. Accepted
12 December2006.
The Amazon Basin contains the most spec- recently, flooded forests have not captured the
tacular river system on earth. Not only is the attention of avian biogeographers (Cohn-Haft
Amazon River the longest and largest river in et al. in press), who have focused mostly on
the world, but some of its tributaries also rate describing bird distribution patterns and gen-
among the 10 largest (Goulding et al. 2003). erating evolutionary hypotheses for Amazo-
These rivers create the Amazonian flood nian terrafirme forests (e.g.. Sick 1967, Haf-
plains, a mosaic of habitats which remain fer 1969, Nores 1999). We attribute this lack
flooded for as much as 8 months every year of interest in the biogeography of flooded for-
(Junk 1989). These seasonally flooded habi- est birds, in part, to the general assumption
tats, known in Brazil as vdrzeas and igapos, that these birds, by living in dynamic and rel-
include floating meadows, sandbar scrub, riv- atively ephemeral habitats, must have strong
er-edge forest, and tall flooded forest each dispersal abilities. Strong dispersal abilities in
hosting a diverse and highly specialized avi- continuous, linearenvironments should not fa-
fauna that accounts for at least 15% of Ama- vor genetic isolation and differentiation of
zonia’s overall non-aquatic bird diversity populations, leading to the expectation of
(Remsen and Parker 1983). widespread species with little or no geograph-
Despite the continental extent of this eco- ic variation (Remsen and Parker 1983). The
system, which ranges thousands ofkilometers lack of precise distributional data for vdrzea
across northern South America, from the base birds has also prevented ornithologists from
of the Andes to the Atlantic Ocean, the dis- making historical interpretations that go be-
tribution, ecology, and evolutionary history of yond a handful of species (e.g., Haffer and
its avifauna have been poorly studied. Until Fitzpatrick 1985, Haffer 1997, Isler et al.
1999, Aleixo 2006).
' Institute Nacional de Pesquisas da Amazonia - The Rio Branco is unique in Amazonia, be-
qIuNiPsAa,s Ceomle9EcooelsogZioao,loCg.iPc.as47e8,CoMoarndaeunsa,^aAomadezoPneass- cause it is a nutrient-rich, semi-muddy river,
69011-970, Brazil. surrounded by black-waterrivers (poorin sed-
^Rua Samaumas 214, Aleixo, Conjunto Acariquara, iments and nutrients, but rich in organic mat-
Manaus, Amazonas 69085-410, Brazil. ter). The ‘color’ of the water has important
^Av. Forest 1531 1° B, (1430), Buenos Aires, Ar- ecological implications, because muddy and
gentina. semi-muddy rivers (hereafter ‘white-water’
Currentaddress: MuseumofNatural Science,Lou-
isiana State University, 119 Foster Hall, Baton Rouge, rivers) differ from black-water rivers not only
LA 70803, USA. in the amount of sediments they carry, but
^Corresponding author; e-mail: [email protected] also in the structure and composition of the
439
440 THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 119, No. 3, September2007
vegetation along their margins (Klinge and in the world. The basins ofthe Rio Negro and
Furch 1991), affecting the species richness Rio Branco jointly contribute nearly 15% of
and composition of its associated avifauna the total annual discharge ofthe Amazon Riv-
(Rosenberg 1990, Petermann 1997, Borges er and occupy an area of roughly 700,000
and Carvalhaes 2000). Many widespread km^, more than 10% of the Amazon Basin
flooded-forest birds occur in riverine habitats (Goulding et al. 2003). The Rio Branco is not
created by both types of rivers, but some are as turbid as the Amazon orthe Madeira rivers,
restricted to either black-water or white-water but its waters contrast strongly with the dark
rivers. White-water river specialists that are waters ofthe Negro. On satellite imagery, this
present on the Rio Branco are necessarily iso- “meeting ofthe waters” can be seen for more
lated from other white-water drainages of than 50 km downstream from their conflu-
Amazonia, potentially allowing genetic and ence.
population differentiation. We divide the Rio Branco in two main geo-
The Rio Branco Basin lies in a region of graphical and ecological regions: the upper
high habitat heterogeneity and of great eco- and lower Rio Branco with the city of Cara-
logical and biogeographical interest, important caraf (01° 50' N) as the dividing point. About
for our understanding of distributional pat- 70 km north of Caracarai, coinciding with the
terns of Amazonian birds (Naka et al. 2006). confluence ofthe Rio Branco and the Rio Mu-
The only major ornithological explorations on cajai, rainfall decreases sharply (Barbosa
the Rio Branco until the mid 20th century 1997) and soil conditions change drastically
were those of Natterer in 1831 and 1832 (von (Brown and Prance 1987). Savannas replace
Pelzeln 1868-1871). More recently, Stotz lowland Amazonian forests in this region and,
(1997) and Zimmer et al. (1997) surveyed the along the rivers, gallery forests replace flood-
river, but like Nattereronly explored the upper ed forests. We have not sampled the Rio Bran-
Rio Branco, where river-created habitats con- co between Caracarai and Mucajai, and do not
sist of narrow stretches of gallery forest. The know how gradually these changes occur.
avifaunas of gallery and flooded forests are However, apparently many flooded-forest bird
generally distinct; the former being more species readily found around Caracarai are not
closely related to dry forests in the savannas present in the gallery forests of the Rio Mu-
than to Amazonian flooded forests. The first cajai or Rio Branco from Mucajai north.
comments on the birds ofthe lower Rio Bran- The terms vdrzea and igapo are local terms
co were published by Pacheco (1995) after a used to describe flooded forests and are often
short visit to the mouth of the river and by used interchangeably by local inhabitants.
Santos (2004), who worked on several river Here, we follow Prance (1979) using these
islands near Caracarai. terms to distinguish forests based on the kind
This paper reports our most interesting ob- of water that floods them: vdrzea for forests
servations obtained during several avifaunal flooded by white (muddy) waters and igapo
surveys on the lower Rio Branco since 1990, for forests flooded by black (translucent, acid-
including several significant range extensions ic) waters. The banks ofthe lower Rio Branco
and 16 species new to the Rio Branco Basin are covered by extensive vdrzeas, whereas
and the State of Roraima. We discuss the bio- many ofits tributaries (i.e., Agua Boa do Uni-
geographical implications ofthese records and vini, Irua, and Ajarani) are black-water rivers,
call attention to the presence of previously whose margins are covered by igapo.
overlooked and possibly isolated populations The Rio Branco has an average river-level
of white-water river specialists on the Rio fluctuation of 5.7 m, which is enough to flood
Branco. large areas along the river, and to ‘dam’ small-
METHODS er tributaries (Goulding et al. 2003). Vegeta-
tion structure and floristic composition depend
—
Study Area. The Rio Branco Basin is on the duration and level ofthe flooding; areas
within the Brazilian State of Roraima (Fig. 1) flooded for longer periods tend to support
and the river is the largest tributary ofthe Rio fewer tree species (Junk 1989). The vdrzeas
Negro, itself the second-largest tributary of ofthe Rio Branco have a well-developed can-
the Amazon and the largest black-water river opy reaching 20-25 m in height, and the un-
Naka et at. • BIRDS OF THE RIO BRANCO FLOODED FORESTS 441
VENEZUELA GUYANA
State of Boa Vista
Roraima
Mucajai
i^Caracarai
Lower Rio Branco
Banta Maria do Boiagu
Mariua^^^Hjg
Archipelago
io
State of
Amazonas
Anavilhanas Archipelago
^
.
Rio AmazonasiS
Rio Solimoes
FIG. 1. The Rio Branco Basin and study localities, enclosedby the Brazilian State ofRoraima, andincluded
within the Rio Negro Basin. White-water rivers are white; black-waterrivers are black. Stippled areasrepresent
reserves. Numbers represent the following rivers or localities: (1) Rio Mucajai, (2) Rio Ajaranf, (3) Niquia
Ecological Station, (4) Virua National Park, (5) Rio Irua, (6) Rio Anaua, (7) Rio Catrimani, (8) Rio Agua Boa
do Univini, (9) village of Samauma on the Rio Jauaperi, (10) Parana da Floresta, (11) Marari Island, and (12)
Inajatuba island. Digital data obtained from Ministerio do Meio Ambiente (2001).
derstory is generally open and poorly devel- range from sandbars to river-edge forest
oped. Tree species diversity and complexity of (dominated by Cecropia) to mature vdrzea
vertical structure on river islands increase as forest, which has the highest number of tree
an island ages (Robinson and Terborgh 1997) species (Remsen and Parker 1983). Igapds are
creating a series of successional stages that usually associated with sandy soils and have
442 THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 119, No. 3, September 2007
fewer tree species than vdrzea forests, narrow- Committee (Comite Brasileiro de Registros
er tree diameters, and a lower canopy height Ornitologicos 2006).
(15-20 m). The physiognomy and floristic
RESULTS
composition of the igapo resemble that of
white-sand forests (Anderson 1981). We present details of 20 species recorded
—AW
Field Work. visited the lower Rio during our fieldwork which represent either
Branco near the mouth of the river on 10-11 new records for the Rio Branco Basin and the
June and 22-24 December 1990, 6-7 April State of Roraima (species marked with an as-
1991, 19-20 August 1993, 25-26 January and terisk), or note-worthy range extensions.
25-26 July 1994, 24-25 March and 15-16
July 1995, and 9-10 June 1996. MCH made Species Accounts
a short visit to the mouth of the Rio Branco *Leuc—opAtWernis schistaceus (Slate-colored
on 6 July 1999. In 2001 and 2006 we joined Hawk). found two single individuals on
three expeditions sponsored by the Instituto river islands on the lower Rio Branco (15 and
Brasileiro do Meio Ambiente e dos Recursos 27 km north of the river’s mouth) on 10 June
Naturals Renovdveis (IBAMA) to survey the 1990 and 7 April 1991, respectively. In Oc-
avifauna of the lower Rio Branco and some tober 2001 LNN and JMB observed and tape-
of its tributaries. Between 6 and 1 1 July 2001, recorded two birds in tall vdrzea forest along
LNN and MFT covered —100 km of the Rio the east bank of the lower Rio Branco (01°
Branco (from Santa Maria do Boia^u to the 36'20"N, 61° 13' 08" W) at Virua National
mouth of the river), a short stretch of the Rio Park. This species seems to be restricted to
Negro influenced by the Rio Branco (Parana tall flooded forests in Brazil (Bierregaard
da Floresta), and the west bank of the Rio 1994) and probably occurs in the State of Ro-
Jauaperi (from its mouth to the village of Sa- raima only along the lower Rio Br—ancAoW.
*Asio stygius (Stygian Owl). ob-
mauma). Between 5 and 18 October 2001,
LNN and JMB covered —170 km of the Rio served one bird perched on a sand bar of a
river island 25 km north of the mouth of the
Branco from Caracarai south to the mouth of
Rio Branco on the night of 22 December
the Rio Catrimani and some Rio Branco trib-
1990. In subsequent visits to that island the
utaries (Agua Boa do Univini, Irua, Anaua,
following day and following year (April 1991)
2a0n0d6A,jaLrNanNi rainvdersM).CHBe,twaececnom1paanndie1d5bOyctMoabre-r AW repeatedly found an individual there (pre-
sumably the same bird). This species is widely
celo dos Santos Jr. and Catherine L. Bechtoldt, distributed from Mexico to Argentina, but
studied —80 km of the Rio Branco from Car-
seems to be rare and local (Marks et al. 1999).
acarai to the confluence with the Rio Anaua, This owl generally inhabits savannas in Am-
and another 35 km up the white-waters of the AW
azonian Brazil, but in recent years has
Rio Anaua and a similar distance along the obtained several records from areas associated
black-waters of the Rio Irua. with black-water rivers and river islands.
We usually conducted bird surveys during *Monasa nigrifrons (Black-fronted Nun-
early morning (0500-1200 hrs), late afternoon bird).—AW found this species along the lower
(1500—1830 hrs), and sporadically at night us- Rio Branco on 23 December 1990 and in suc-
ing binoculars and tape-recorders. We ex- cessive trips to the same general area. Sub-
plored river-created habitats {vdrzea and iga- sequently, LNN, JMB, and MFT observed and
pd) using small motorboats, which allowed tape-recorded several individuals in vdrzea
access to the forest interior. LNN and MCH forest along both banks ofthe lowerRio Bran-
collected bird specimens, housed at the Insti- co. Our records ranged from the mouth ofthe
tuto Nacional de Pesquisas da Amazonia river north to the island of Inajatuba (01° 17'
(INPA) Bird Collection in Manaus, Brazil. 22" N, 61° 18' 04" W), nearly 60 km south of
Tape-recordings by LNN and MCH are ar- Caracarai. This species is widespread in Ama-
chived at the INPA Bird Collection; those by zonia, mostly restricted to flooded forests
AW
are at the British Library National Sound (Rasmussen and Collar 2002), but seems to be
Archive. Taxonomy and species nomenclature restricted in the State of Roraima to the vdr-
follow the Brazilian Ornithological Records zeas of the lower Rio Branco, with no known
Naka et al. • BIRDS OF THE RIO BRANCO FLOODED FORESTS 443
records from gallery forests further north or mouth of the river north to the island of Ina-
from Venezuela (Hilty 2003). jatuba where it was fairly common. Addition-
*Myrmotherula klagesi (Klages’ Ant- ally, LNN and MFT tape-recorded several in-
—AW
wren). heard and observed several pairs dividuals along the Parana da Floresta on the
in mature vdrzea forest —20 km north of the Rio Negro. On 15 October 2006 LNN tape-
mouth of the Rio Branco on 23 December recorded and collected a pair on the left bank
1990. Birds were subsequently tape-recorded of the Rio Branco (01° 31' 06" N, 61° 14' 25"
AW
by along both banks of the Rio Jauaperi W). Three other individuals had been collect-
in August 1993 and other sites along the lower ed earlier by M. P. D. Santos from Virua Na-
MCH
Rio Branco in June 1993 and July 1995. tional Park and Sao Joao da Baliza in August
tape-recorded the species near the mouth of 2002 and January 2003, respectively. Most of
the Rio Branco in July 1999, and in July and the known range of C. nigrescens is restricted
October 2001, LNN and MFT, and LNN and to areas south of the Amazon from eastern
JMB, respectively, documented its presence Colombia to the Brazilian State of Para (Zim-
throughout the lower Rio Branco, obtaining mer and Isler 2003). The only known popu-
tape-recordings from the mouth ofthe river as lations north of the Amazon are represented
far north as the island ofInajatuba, 300 km to by the nominate race, which occurs in Suri-
the north. On 6 October 2006 MCH tape-re- nam, French Guiana, and along the north bank
corded and collected a male from a river is- of the Amazon in the Brazilian State of Para
land on the Rio Branco, opposite the mouth (Pinto 1978, Haverschmidt and Mees 1994).
of the Rio Anaua, representing the first spec- These are the first published records of C. ni-
imen for the State ofRoraima. Previously, this grescens from the Rio Branco and are sepa-
species was known to occur on the lower Rio rated by —360 km and more than 600 km
Negro and along the Amazon, including the from nearest localities to the south and north,
Rio Madeira and the mouth ofthe Rio Tapajos respectively, apparently representing a dis-
(Zimmer and Isler 2003). Our records extend junct population.
the known distribution ofM. klagesi well into Cercomacra carbonaria (Rio Branco Ant-
—
the Rio Branco Basin and more than 300 km bird). This taxon was considered to be strict-
northward from previous known sites on the ly associated with gallery forests along the up-
Rio Negro. per Rio Branco and some of its tributaries
*My—rmAotWherula assimilis (Leaden Ant- (Stotz 1997, Zimmer et al. 1997, Santos 2003,
wren). observed this species in tall vdr- Zimmer and Isler 2003). In July and October
zea forest —20 km north of the mouth of the 2001, LNN and MFT, and LNN and JMB, re-
Rio Branco on 10 June 1990 and several other spectively, found and tape-recorded several
times in the same general area. In July and individuals along the lower Rio Branco where
October 2001, LNN and MFT, and LNN and it was locally common in young riverine is-
JMB, respectively, tape-recorded this species lands dominated by Cecropia spp. In October
throughout the lower Rio Branco, as far north 2006, LNN and MCH also found the species
as the island of Inajatuba, and also along the to be common on riverine islands from Car-
Anaua and Jauaperi rivers. This species is acarai south to the mouth of the Rio Anaua.
known to be widespread in flooded forests Our records extend the known range of this
throughout much of Amazonia (Zimmer and species south ofCaracarai (previously consid-
Isler 2003), but was previously unrecorded ered its southernmost limit) to only 13 km
from the Rio Branco Basin. north from the mouth of the Rio Branco (01°
*Cercomacra nigrescens (Blackish Ant- 16' 19" S, 61° 50' 21" W). We do not expect to
—MCH
bird). tape-recorded this species in find this species anywhere outside the Rio
Roraima at the mouth of the Rio Branco on 6 Branco Basin or in adjacent black-waterrivers
July 1999. Subsequently, in July and October where successional river islands do not occur.
2001, LNN and MFT, and LNN and JMB, re- We failed to find C. carbonaria in tall vdrzea
spectively, saw and tape-recorded several in- forests where C. nigrescens was present sug-
dividuals in mid-successional vegetation on gesting that species interactions and habitat
riverine islands and forest edges along both preferences may limit its distribution within
banks of the lower Rio Branco from the the Rio Branco Basin. Our records along the
444 THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 119, No. 3, September2007
—
lower Rio Branco suggest that C. carbonaha tail). LNN and JMB found and tape-record-
has greater ecological plasticity than previ- ed one individual in mature vdrzea forest at
ously thought and represent a range extension the Niquia Ecological Station (00° 50' 08" N,
of more than 300 km southward, doubling the 61° 25' 45" W) on 6 October 2001. On 9 Oc-
size of its global distribution. At present, C. tober 2006 LNN tape-recorded and collected
carhonaria is considered Vulnerable to ex- a male in tall vdrzea forest along the Rio An-
tinction by BirdLife International (2000), but aua (00° 57' 20" N, 61° 09' 22"W). These are
was recently excluded from the Brazilian list the first records from the Rio Branco Basin
of threatened birds (Ministerio do Meio Am- although this species is relatively widespread
biente 2003) based on lack of data. More re- in Amazonian flooded forests and is present
cently, Vale et al. (in press) suggested down- along the lower Rio Negro (Cintra et al.
listing the species to near-threatened, in part 2007).
due to the significant range extensions here *Hemitriccus minor (Snethlage’s Tody-ty-
—AW
presented. rant). saw and tape-recorded one indi-
^Sclateria naevici (Silvered Antbird).—AW vidual 20 km north of the mouth of the Rio
found a vocalizing male 25 km north of the Branco on 20 August 1993. Subsequently,
MCH
mouth of the Rio Branco on 16 July 1995. found this species in Roraima at the
Subsequently, LNN and MFT observed and mouth of the Rio Branco in July 1999, and in
tape-recorded a pair along a dry stream near July and October 2001, LNN and MFT, and
Sao Joao da Baliza at the edge ofthe Wai-Wai LNN and JMB, respectively, found it along
Indian Reservation (01° 05' 21" N, 59° 56' most ofthe lower Rio Branco and otherblack-
37" W) in March 2001 and, in October 2006, water tributaries, including the Agua Boa do
LNN and MCH found several birds along the Univini and Ajarani rivers (our northernmost
Rio Anaua. These are the first records for the locality in Roraima). Our records seem to re-
region and fill what had appeared as a some- fer to the race pollens, which is a flooded-
what inexplicable gap in its distribution (Zim- forest inhabitant common along the middle
mer and Isler 2003). and lower Rio Negro.
Synallaxis propinqiui (White-bellied Spine- Serpopluigci hypoleuca (Riverside Tyran-
—AW —AW
tail). found several individuals vocaliz- nulet). found a pair on a young river
ing in early-SLiccessional vegetation on a river island 27 km north from the mouth ofthe Rio
island 27 km north of the mouth of the Rio Branco on 21 March 1993. This species was
Branco on 21 March 1993. One individual also recorded on the lower Rio Branco by Pa-
was tape-recorded by Pacheco (1995) in Oc- checo (1995). Prior to these records, this ear-
tober 1993 near the mouth of the Rio Branco. ly-successional vegetation inhabitant was
In October 2006, LNN and MCH found sev- known from several white-water rivers in the
eral individuals on a young river island along Amazon Basin, but not from the Rio Branco
the Rio Branco, opposite the mouth ofthe Rio or the Rio Negro basins (Fitzpatrick 2004).
Anaua, and on two other river islands. On 14 *Stigmatiira napensis (Lesser Wagtail-ty-
MCH —AW
October 2006 tape-recorded and col- rant). found a pair in early-successional
lected one male on the island of Marari (01° vegetation on a river island 27 km upstream
28' 42" N, 61° 14' 58" W) where two pairs from the mouth of the Rio Branco on 21
were building nests. Previous to these records, March 1993. On 13 October 2006 MCH and
this spinetail was known to occur locally in LNN tape-recorded and collected a pair in ear-
early-successional growth on river islands ly successional vegetation on the island of
along the Amazon River and some of its Marari. Several other pairs were located on
white-water tributaries (Remsen 2003). Our the same island the following day. The female
records not only document the presence ofthis collected had unshelled eggs in the ovary,
species in the Rio Branco Basin, but also sug- suggesting that individuals were reproducing
gest the presence ofa breeding population iso- on this island. Prior to our records, the Ama-
lated from the main populations distributed zonian form (nominate race) of this species
contiguously along the Amazon River and its was known to occur exclusively along white-
tributaries. water Amazonian rivers south ofthe Amazon,
"^Crcmioleuca gutturatci (Speckled Spine- especially on newly-formed sandbars with
— —
Naka et al. • BIRDS OF THE RIO BRANCO FLOODED FORESTS 445
bushes of the genus Tessaria (Fitzpatrick Rio Agua Boa do Univini. One bird was col-
2004). We believe this species is absent from lected in Virua National Park in August 2002
the Rio Negro and that birds recorded on the by M. P. D. Santos (held at MPEG) repre-
Rio Branco represent an isolated population. senting the first specimen for the State of Ro-
Another isolated population was recently raima. Several other birds were also heard
found on the upper Orinoco River (Hilty along the Rio Anaua by LNN and MCH in
2003). October 2006 indicating the presence of this
*Inezia subflava (Amazonian Tyrannu- species was previously overlooked in the re-
—AW
let). heard several pairs in flooded veg- gion.
etation at a lake edge 20 km north of the *Hylophilus semicinereus (Gray-chested
—AW
mouth of the Rio Branco on 23 December Greenlet). heard one bird vocalizing
1990 and 23 March 1995. MCH, LNN, and near the mouth of the Rio Branco on 21 De-
MFT encountered and tape-recorded this spe- cember 1990. Subsequently, in July 2001,
cies in Virua National Park in March 2001. LNN and MFT observed and tape-recorded
Subsequently, in July and October 2001, LNN several individuals in tall vdrzea and igapo
and MFT, and LNN and JMB, respectively, forest along the lower Rio Branco and Rio
found /. subflava to be fairly common in vdr- Jauaperf and, in October 2001, LNN and JMB
zea and igapo edges along the lower Rio tape-recorded several individuals within the
Branco and some black-water tributaries such Niquia Ecological Station and Virua National
as the Agua Boa do Univini, Irua, and Jauap- Park. On 9 October 2006 LNN tape-recorded
eri rivers. Previous specimens from the State and collected a male from a campinarana-vdr-
ofRoraima collected by Natterer (von Pelzeln zea transition zone on the right bank of the
1868-1871), Pinto (1966), Emflio Dente (held Rio Anaua (00° 57' 33" N, 61° 09' 30" W),
at Museu Paraense Emflio Goeldi, MPEG), finding several other individuals along this
and D. F. Stotz (held at the Field Museum of river and the Rio Irua. This species is rela-
Natural History) were taken from the upper tively abundant along the Rio Negro and our
Rio Branco (and other rivers within the sa- records fill a sampling gap in its distribution
vannas domain) and apparently refer to /. cau- (Ridgely and Tudor 1989).
data, now considered a separate species (Zim- Conirostrurn bicolor (Bicolor Conebill).
mer and Whittaker 2000). Our records repre- LNN and MFT found and tape-recorded two
sent the first for /. subflava on the Rio Branco individuals on a river island (01° 16' S, 61°
and in the State of Roraima. Inezia subflava 50' W) dominated by Cecropia. On 6 October
MCH
(a flooded-forest inhabitant) and /. caudata (a 2006 tape-recorded and collected a
gallery forest species) seem to replace each male from a group of three birds on an early
other ecologically and geographically, with successional river island on the Rio Branco
the region of turnover somewhere near Cara- opposite the mouth of the Rio Anaua. LNN
MCH
carai. and found this species to be abundant
*Conopias trivirgatus (Three-striped Fly- on other river islands between Caracarai and
—AW
catcher). saw a pair at the mouth of the the mouth of the Rio Anaua suggesting that
Rio Jauaperf on 25 July 1994. Subsequently, C. bicolor has permanent populations along
AW
tape-recorded a few individuals in July this stretch of the river. This species has two
1995 in transitional vdrzea forest —20 km distinct populations in the Neotropics; one in-
north of the mouth of the Rio Branco. The habiting mangroves in coastal areas in north-
distribution of this species is poorly known ern South America and the other inhabiting
with several disjunct populations throughout early-successional vegetation in Amazonia,
tropical South America (Fitzpatrick 2004). mainly along the Amazon and some tributar-
^Schijfornis major (Varzea Schiffornis). ies (Ridgely and Tudor 1989). This species
AW
heard and observed several birds in vdr- has been previously recorded along the lower
zea forest near the mouth of the Rio Branco Rio Branco by Pacheco (1995) and our rec-
on 7 April 1991. In October 2001, LNN and ords further extend its distribution 260 km to
JMB saw and tape-recorded individuals in tall the north, representing the northernmost lo-
vdrzea along the lower Rio Branco (00° 50' calities within the Amazon Basin.
08" N, 61° 25' 45" W) and in igapo along the *Ammodramus aurifrons (Yellow-browed
446 THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 119, No. 3, September2007
Sparrow).—AW saw two pairs along the edge place humid forests less than 100 km south of
of a river island 27 km north from the mouth Boa Vista.
of the Rio Branco on 14 April 1991. Subse- Most typical vdrzea bird species such as
quently, in July 2001, LNN and MFT saw and Leucopternis schistaceus, Monasa nigrifrons,
tape-recorded several individuals around the Xiphorhynchus kienerii, Thamnophilus nigro-
villages of Floresta and Samauma. In October cinereus, Myrmotherula klagesi, M. assimilis,
2001, LNN and JMB found this species to be Myrmoborus lugubris, and Hemitriccus minor
locally common along sand-banks and sand- seem to reach their northernmost limit in this
bar scrub on river islands along the lower Rio area. The shift in habitat seems also to be re-
Branco from the mouth of the river extending sponsible for ecological substitutions between
to 50 km south of Caracarai (01° 36' 19" N, closely related taxa from vdrzea and gallery
61° 13' 27" W). On 13 October 2006, LNN forests (i.e., Inezia subflava and /. caudata,
tape-recorded and collected a male on a sandy and Amrnodramus aurifrons and A. humeral-
beach on a river island on the Rio Branco is).
(01° 14' 00" N, 61° 19' 01" W). These records The Rio Branco is unique in representing a
indicate this species is widespread in the re- white-water river surrounded by black-water
gion and was previously overlooked due to a drainages including the Negro, Jauaperi, Agua
sampling gap. Boa do Univini, Ajarani, and Irua rivers (Fig.
"^Sicalis—CoAlWumbiana (Orange-fronted Yel- 1). Despite the high similarity between avian
low-finch). found several individuals communities ofthe vdrzeas ofthe Rio Branco
along the edge of a river island on the lower and the tall igapd of the lower Rio Negro,
Rio Branco on 21 December 1990. Subse- several elements typical of Amazonian white-
quently, in July 2001, LNN and MFT saw and water rivers are present on the Rio Branco,
tape-recorded more than 20 individuals at the but seem to be absent from the entire Rio Ne-
village of Floresta on the Parana da Floresta. gro and its black-water tributaries. We discov-
These seem to represent the first and only rec- ered populations of Cercomacra nigrescens
ords of its occurrence within the Rio Branco and Stigmatura napensis along the lower Rio
Basin and the State of Roraima. Branco, and also confirmed the presence of
species previously reported from the mouth of
DISCUSSION
the Rio Branco by Pacheco (1995), such as
Our studies along the lower Rio Branco re- Synallaxis propinqua, Serpophaga hypoleuca,
vealed that south of Caracarai, the avifauna and Conirostrum bicolor. These species, with
associated with the river floodplains is repre- the exception of Cercomacra nigrescens,
sented by typical flooded-forest species, sim- which also occurs in terrafirme forest in part
ilar to those in the Anavilhanas Archipelago of its range, are typical white-water river-is-
and the lower Rio Negro (Cintra et al. 2007). land specialists (Ridgely and Tudor 1989,
Environmental variables such as soil, flooding 1994; Rosenberg 1990; Robinson and Ter-
regimes, and rainfall differ between the lower borgh 1997; Remsen 2003). Repeated records
Rio Branco and the upper portions ofthe river from the area since 1993 suggest these species
where tall vdrzea forests are replaced by gal- maintain stable populations locally, rather
lery forests. Bird species composition on the than representing vagrants or dispersing indi-
lower Rio Branco is generally similar to that viduals. Supporting this hypothesis are data
of other Amazonian rivers, such as the Ama- that we obtained of unequivocal breeding ev-
zon, Madeira, and the lower Rio Negro. The idence for Stigmatura napensis and Synallaxis
avifauna of the upper Rio Branco, however, propinqua.
seems to be more closely related to gallery Most vdrzea birds are believed to be excel-
and dry semi-deciduous forests typical of the lent dispersers (Remsen and Parker 1983) and
savannas of northern Roraima, Guyana, and these abilities should be enhanced by having
Venezuela. The transition zone between the linear and uninterrupted habitats. The exis-
two habitats seems to be quite abrupt, occur- tence of isolated populations of white-water
ring within the 70-km stretch between Cara- specialists along the lower Rio Branco could
carai and the mouth of the Rio Mucajaf, co- either be the result of remarkably long-dis-
inciding with the region where savannas re- tance dispersal or represent relict populations
Naka et al. • BIRDS OF THE RIO BRANCO FLOODED EORESTS 447
from once-continuous habitats. Whether these Jurgen Haffer, Daniel Lane, J. V. Remsen Jr., and an
populations are old or relatively recent, their anonymous reviewer made helpful comments on pre-
vious versions ofthe manuscript thatgreatly improved
isolation provides an opportunity for genetic this paper. LNN had a Conselho Brasileiro de Desen-
differentiation and endemism in vdrzea forest. volvimento Cientifico e Tecnologico (CNPq)/INPA
Geomorphological data are still equivocal (DTI) fellowship during the period he developed field
on past connections of Amazonian rivers, but work in Roraima in 2003, and a CNPq Overseas Doc-
fish communities of the Rio Branco seem to toral Eellowship in 2006 (grant #202131/2006-8).
be more closely related to those of the Ama- BirdersExchangekindlydonatedopticalandrecording
zon River than to those ofthe Rio Negro (Jan- equipment to the INPA ornithological collection. This
zen Zuanon, pers. comm.). Recent Parsimony anrittihcolelorgeyprTeescehnntiscaPlubSleirciaetsioonft4heinItNhPeAASmcaizenotniifiacnCoOlr--
Analysis ofEndemicity (PAE) forcharaciform lections Program.
fishes produced an area of purported ende-
mism including the Rio Branco, the lower Rio LITERATURE CITED
Negro, and the lower Amazon excluding the Aleixo, a. 2006. Historical diversification of flood-
upper Rio Negro and other portions of the plain forest specialist species in the Amazon: a
Amazon River (Hubert and Renno 2006). This case study with two species of the avian genus
implies the lower Rio Negro may not be as Xiphorhynchus (Aves: Dendrocolaptidae). Biolog-
strong a barrier for these fishes as we believe ical Journal ofthe Linnean Society 89:383-395.
Anderson, A. 1981. White-sand vegetation of Brazil-
it is for white-water specialist birds. Rossetti ian Amazonia. Biotropica 13:199-210.
et al. (2005) suggested the existence ofa body Barbosa, R. I. 1997. Distribuigao das Chuvas em Ro-
of water connecting the upper Amazon River raima. Pages 325-335 in Homem, ambiente e
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tence of recently isolated populations of stituto Nacional de Pesquisas da Amazonia, Ma-
naus, Brazil.
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Bierregaard, R. O. 1994. Family Accipitridae (hawks
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ACKNOWLEDGMENTS tional, Barcelona, Spain.
Borges, S. H. and A. Carvalhaes. 2000. Birdspecies
We are particularly grateful to the Instituto Brasi- of black water inundated forests in the Jail Na-
leiro do Meio Ambiente e dos Recursos Naturais Re- tional Park (Amazonas State, Brazil): theircontri-
novdveis (IBAMA) in Roraima forallowingcollecting bution to regional species richness. Biodiversity
and access to parks and otherconservation unitsunder and Conservation 9:201-214.
its jurisdiction. We extend our gratitude to Antonio Brown, K. S. and G. T. Prance. 1987. Soils and veg-
Galdino and Antonio and Beatriz Lisboa fortheirsup- etation. Pages 19-45 in Biogeography and Qua-
port in Caracarai, and for inviting us to participate in ternary history in tropical America (T. C. Whit-
three expeditions sponsored by the Institute. We also more and G. T. Prance, Editors). Clarendon Press,
extend our gratitude to A. F. Coutinho Mello, Otacilio Oxford, United Kingdom.
de SouzaNevesJr., InaraRochaSantos,GiovannaPal- CiNTRA, R., T. M. Sanaiotti, and M. Cohn-Haft.
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gistical support in Boa Vista. We thank Luiz Mestre, Cohn-Haft, M., L. N. Naka, and A. M. Fernandes.
Catherine Bechtoldt, and Marcelo dos Santos Jr. for In press. Padroes de distribui^ao da avifauna da
their company during some of the field trips. AW varzea do rio Solimoes-Amazonas in Bases cien-
thanks Mark Baker ofEco Tours for allowing him the tificas para a conservacao da varzea: identifica^ao
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