WILSON BULLETIN Thursday Jan 05 2006 04:24 PM wils 118_103 Mp_13 Allen Press • DTPro System GALLEY File # 03TQ

The Wilson Journal of Ornithology 118(1):13±22, 2006

THE REDISCOVERY AND NATURAL HISTORY OF THE WHITE-MASKED ANTBIRD (PITHYS CASTANEUS)

DANIEL F. LANE,1,6 THOMAS VALQUI H,1,2 JOSEÂ ALVAREZ A,3 JESSICA ARMENTA,2,5 AND KAREN ECKHARDT4

ABSTRACT.ÐIn July 2001, a Louisiana State University Museum of Natural Science expedition rediscovered the White-masked Antbird (Pithys castaneus) at a site along the RõÂo Morona in northwestern Departmento Loreto, Peru. Prior to this rediscovery, the species was known only from the type specimen, taken in 1937, and nothing was recorded concerning its natural history. The lack of additional specimens led to speculation that P. castaneus was a hybrid. Here, we present data demonstrating that the White-masked Antbird is a valid species, and we report the ®rst observations of its behavior, habitat, morphology, and voice. Received 14 January 2005, accepted 11 October 2005.

In 1938, Berlioz (1938) described a distinc- to be a sympatric congener. It differed from tive new species of antbird in the genus Pith- P. albifrons in its larger size, its lack of any ysÐuntil then considered monotypicÐfrom a gray on the body, and its lack of elongated single specimen collected by Ramon Olalla on plumes on the face or throat. 16 September 1937 at ``Andoas, lower [RõÂo] Decades passed without any additional re- Pastaza, eastern Ecuador.'' This new species, cords of P. castaneus. Subsequent authors the White-masked Antbird (Pithys castaneus), doubted the validity of the species, and many has remained one of the most intriguing mys- suggested that it represented nothing more teries of Neotropical ornithology for over 60 than a hybrid of P. albifrons and another ant- years (see David and Gosselin 2002 for gen- bird species (Sibley and Monroe 1990, Schu- der of scienti®c name). Besides the collector, lenberg and Stotz 1991, Collar et al. 1992, no biologist had ever seen the bird alive, and Statters®eld and Capper 2000, Ridgely and there is no information on the species' natural Green®eld 2001b). Willis (1984) and person- history or preferred habitat. The type locality, nel at the Philadelphia Academy of Natural ``Andoas,'' is particularly intriguing in that at Sciences (ANSP; Collar et al. 1992, Ridgely least three sites in the Pastaza area bear this and Tudor 1994) searched without success for name (Stevens and Traylor 1983, Paynter P. castaneus along the upper RõÂo Pastaza in 1993), and according to T. Mark (in litt.), we Peru and Ecuador, respectively. may never really know the true location of the Thus, when our Louisiana State University type locality. Museum of Natural Science (LSUMZ) orni- The type specimen, a male (contra Ridgely thological ®eld team visited several sites in and Tudor 1994), is housed at the Paris Mu- northwestern Departamento Loreto, Peru, seum in France. According to Berlioz (1938, from May through July 2001, it was with great 1948), it was part of a collection that included surprise that we found P. castaneus to be fair- three specimens of White-plumed Antbird (P. ly common at one of our ®eld sites. The main albifrons peruvianus) and therefore appeared goal of our ®eldwork was to inventory the avifauna of two isolated patches of varillal 1 Louisiana State Univ. Museum of Natural Science, (white sand) forest (see Whitney and Alvarez 119 Foster Hall, Baton Rouge, LA 70803, USA. 1998; Alvarez and Whitney 2001, 2003). One 2 Dept. of Biological Sciences, Louisiana State Univ., Baton Rouge, LA 70803, USA. of these forest patches was in the inter¯uvium 3 Inst. de Investigaciones de la AmazonõÂa Peruana between the Morona and Santiago rivers in (IIAP), Av. QuinÄones Km. 2.5, Iquitos, Peru. northern Peru, north of the RõÂo MaranÄoÂn, only 4 Museo de Historia Natural de la Univ. Nacional about 60 km west of the RõÂo Pastaza, and it Mayor de San Marcos, Apartado 14±0434, Lima, Peru. was there that we found P. castaneus. 5 Current address: Dept. of Biological Sciences, P.O. Box 413, Lapham Hall, Univ. of Wisconsin, Milwau- Remarkably, while reviewing specimen ma- kee, WI 53201, USA. terial at the Museo de Historia Natural de la 6 Corresponding author; e-mail: [email protected] Universidad Mayor San Marcos (MUSM), 13 WILSON BULLETIN Thursday Jan 05 2006 04:24 PM wils 118_103 Mp_14 • Allen Press DTPro System GALLEY File # 03TQ

14 THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 118, No. 1, March 2006

FIG. 1. Known localities for Pithys castaneus in northwestern Departmento Loreto, Peru. The star represents suspected location of ``Andoas,'' the type locality, on the RõÂo Pastaza (Berlioz 1938). The square represents the location of the species' rediscovery in July 2001 on the west bank of the RõÂo Morona (04Њ 17Ј S, 77Њ 14Ј W). The Cordillera CampanquõÂs lies between the rõÂos Morona and Santiago, immediately to the west of our ®eld site.

Lima, in November 2002, we discovered two study site was on the south side of the mouth additional specimens of P. castaneus (one of Quebrada CashacanÄo, a right-bank tributary adult and one juvenile). These specimens were of the RõÂo Morona, about 2.3 km north of the reportedly taken somewhere in the Cordillera village of Tierra Blanca. We observed and CampanquõÂs region on the border of Depart- made a general collection of birds at this site mentos Amazonas and Loreto between the between 2 and 21 July 2001. Our camp was Morona and Santiago rivers (see Fig. 1), in set up in a clearing of a homestead abandoned the mid- to late 1990s by a Peruvian anthro- about 30 years earlier and which, reportedly, pologist, Andres Treneman (I. Franke J. pers. has been reinhabited since our visit (B. Walker comm.). Unfortunately, no additional speci- pers. comm.). A preexisting trail, used for the men data are available, and the collector could harvest of palm fronds for thatched-roof con- not be contacted for additional information. struction, led directly into white-sand forests for about 2 km. Another trail, cut along the METHODS bluff above the Morona, connected the camp Locality.ÐWe established a campsite on the with the village of Tierra Blanca. From this west bank of the RõÂo Morona about 54 km trail, at least another three trails also entered north-northwest of its mouth (04Њ 17Ј S, 77Њ the varillal forest. Additional trails were cut 14Ј W; Fig. 1), Departmento Loreto. The near camp for census routes and net lanes; WILSON BULLETIN Thursday Jan 05 2006 04:24 PM wils 118_103 Mp_15 Allen Press • DTPro System GALLEY File # 03TQ

Lane et al. • REDISCOVERY OF WHITE-MASKED ANTBIRD 15

most trails were in varillal, but three also en- 172975, 172976 [skeleton and partial skin], tered the adjacent varzea (seasonally inundat- 172977, 172978, 172979 [skeleton and partial ed) forest. We also found two patches of richer skin], MUSM 23504, 23505, 23506, 23507; clay-soil terra ®rme forest north and south of DFL 1646 [skeleton, uncataloged], TVH 399 the surveyed varillal forest patch, into which [alcohol, uncataloged]). we cut two trails. Pithys albifrons: Ecuador: Pastaza; Coco- Habitat.ÐMost of the forest where P. cas- naco, 300 m elevation (LSUMZ 83237); Peru: taneus was observedÐparticularly away from Amazonas; Huampami, ϳ215 m elevation major water bodiesÐgrew on very moist, (LSUMZ 84917), Chiriaco, ϳ320 m elevation white-sand soils. Numerous areas of wet, (LSUMZ 78514, 88018, 88019, 88022); Lor- swampy conditions indicated a high water ta- eto; Libertad, S bank of RõÂo Napo, 80 km N ble. The terrain was without signi®cant relief, of Iquitos, 120 m elevation (LSUMZ 110094, but throughout the varillal forest were many 110096, 110097, 110098, 110099, 110100, small depressions where water accumulated, 110102, 110103, 110104, 110105); 157 km by particularly after rains, presumably pits re- river NNE of Iquitos, N of RõÂo Napo, 110 m sulting from tree-falls. The soil consisted of elevation (LSUMZ 110106, 110109, 110112, rather coarse sand with stones of up to 5 cm 110113). in diameter (up to 15 cm in the small creeks Gymnopithys leucaspis: Peru: Loreto; west that transected the forest interior). Using a nat- bank of RõÂo Morona, ϳ54 km NNW of the ural cut at the RõÂo Morona riverbank for ref- mouth, 140 m elevation (04Њ 17Ј S, 77Њ 14Ј W) erence, the sandy soil is approximately 4 m (LSUMZ 172985); Quebrada OraÂn, ϳ5kmN deep at the river's edge. Typical of many var- of RõÂo Amazonas, 85 km NE of Iquitos, 110 illal forests, a thick layer of dead leaves and m elevation (LSUMZ 119884, 119885, humus covered the forest ¯oor (Ruokolainen 119886, 119887, 119890, 119891, 119892, and Tuomisto 1993, 1998; Richards 1996). 119893). The forest canopy of the varillal was relative- Phlegopsis erythroptera: Ecuador: Sucum- ly even, with a height of about 20 to 30 m. bios; Limoncocha, 300 m elevation (00Њ 24Ј The relative absence of buttressed trees is typ- S, 76Њ 37Ј W) (LSUMZ 70916, 70917, 70919, ical of varillal forests (Richards 1996); how- 83314). Peru: Loreto; W bank of RõÂo Morona, ever, many such trees were present in more ϳ54 km NNW of the mouth, 140 m elevation humid forest areas at the Morona site. As has (04Њ 17Ј S, 77Њ 14Ј W) (LSUMZ 173001); 1.5 been noted in other varillal forests (Anderson km S of Libertad, S bank of RõÂo Napo, 80 km 1981, Richards 1996), there were few lianas, and epiphytic growth was negligible. N of Iquitos, 120 m elevation (LSUMZ Data collection.ÐWe collected specimens 110213, 110215, 110217); 1 km N of RõÂo using mist nets and shotguns. Permits for Napo, 157 km by river NNE of Iquitos, 110 specimen collection were issued by Peru's In- m elevation (LSUMZ 110219); lower RõÂo ϳ stituto Nacional de Recursos Naturales (IN- Napo region, E bank of RõÂo Yanayacu, 90 RENA). Specimens were deposited into the km N of Iquitos, 120 m elevation (LSUMZ collections of LSUMZ and MUSM. Skull os- 115573). si®cation, gonad information, and presence of Rhegmatorhina melanosticta: Peru: Ama- fat in prepared specimens were determined zonas; headwaters of RõÂo Kagka (of RõÂo Ce- ϳ Њ Ј Њ Ј following standard LSUMZ specimen prepa- nepa), 790 m elevation (04 16 S, 78 09 ration protocol. Natural history information W) (LSUMZ 88028, 88029); San MartõÂn; ϳ15 was acquired through opportunistic (not sys- km by trail NE of Jirillo on trail to Balsa- tematic) encounters with P. castaneus. Spec- puerto, 1,350 m elevation (LSUMZ 116947); trograms of voice recordings were prepared Huanuco; ϳ35 km NE Tingo of MarõÂa, Ha- using Canary sound analysis software (Charif cienda Santa Elena, ϳ1,000 m elevation et al. 1995). (LSUMZ) ; Pasco; Abra Aguachini, ϳ30 km Specimens examined.ÐPithys castaneus: SW of Puerto Bermudez, 1,020 m elevation Peru: Loreto; west bank of RõÂo Morona, ϳ54 (LSUMZ 130274); Pasco; Puellas, km 41 on km NNW of the mouth, 140 m elevation (04Њ Villa Rica±Puerto Bermudez highway, 950 m 17Ј S, 77Њ 14Ј W) (LSUMZ 172973, 172974, elevation (LSUMZ 106073, 106074, 106078). WILSON BULLETIN Thursday Jan 05 2006 04:24 PM wils 118_103 Mp_16 • Allen Press DTPro System GALLEY File # 03TQ

16 THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 118, No. 1, March 2006

RESULTS

Specimen data.ÐWe collected 13 speci- 0.7 1.2 0.4 0.4 0.4 0.6 0.6 0.5 0.3 0.6

mens of Pithys castaneus during our visit to Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ the RõÂo Morona site. We prepared nine as study skins (from which several trunk skele- tons were saved), three as complete skeletons (from which two partial skin specimens were saved), and one was preserved whole in al- 00.50.70.8 12.0 0.5 12.0 1.2 10.9 1.7 10.6 1.4 11.8 1.2 11.0 0.8 12.9 12.0 12.4 11.7

cohol. Mass and lengths of ¯at-wing, tail, tar- Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ sus, and culmen (from distal edge of the nares to bill tip) of all specimens are presented and compared with measurements of the P. cas- taneus holotype and other Peruvian antswarm-

following antbirds (Table 1). . Three of the 12 specimens in ``adult'' plum- 1.92.91.51.1 25.0 0.9 24.4 2.1 22.2 2.4 21.5 1.0 26.0 2.0 25.8 2.5 33.5 32.0 27.6 27.4 age (LSUMZ 172973, MUSM 23504, MUSM Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ 23507) still possessed a bursa of Fabricius and one had an incompletely ossi®ed skull (75% ossi®cation), suggesting that ®rst basic plum- age is acquired quickly and is nearly indistin-

guishable from de®nitive plumage (but see be- 2.01.72.01.5 52.2 2.3 52.3 1.3 36.4 1.7 35.6 1.3 43.9 5.2 42.9 2.8 63.3 59.0 53.0 49.8

low). One specimen (LSUMZ 172978) was a Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ male still largely in juvenal plumage (skull os- , and associated species from Peru and Ecuador. si®cation 50%, bursa 8 ϫ 6 mm). Of the 12 specimens dissected, only 2Ðboth with im- mature charactersÐwere reported to have P. albifrons

subcutaneous fat deposits: ``trace fat'' in one , 2.71.52.41.3 82.8 2.7 80.6 2.3 67.5 5.2 65.5 7.0 73.5 1.9 71.9 4.7 91.6 88.0 81.3 78.0

and ``light fat'' in the other. Six of 12 speci- Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ

mens dissected exhibited trace or light body Mass (g) Flat wing (mm) Tail (mm) Tarsus (mm) Culmen (mm) molt. Seven individuals had asymmetrical wing molt, and seven had asymmetrical tail

molt. Stomach contents were reported as ``in- Pithys castaneus 1Ð82Ð2315 of

sect parts'' for all specimens in which the n stomachs were not empty. The guts of two a specimens were infested with nematodes. Variation in the series.ÐTwelve speci- mensÐ5 males and 7 femalesÐexhibited similar plumage, with no sexual dichroma- tism. All these adults appeared to match the description of P. castaneus and the photos of the holotype very closely. Of the specimens in ``adult'' plumage, two that appeared to be for catalog numbers and localities of specimens. (males)(females) 4 5 30.0 33.0

in their ®rst year (see above) have very sparse, b SD) measurements of specimens

light-grayish scaling on the center of the (males)(females) 5 5 58.4 58.2 (males)(females) 5 5 23.9 23.8 throat (unmarked white in all other individu- Ϯ als), suggesting that it may be an age-related (holotype) (Morona specimens-females) 5 30.1 (Morona specimens-males) 6 29.6 character. Otherwise, plumage characters were (males)(females) 10 10 18.7 18.5 uniform among all the ``adult'' specimens. Specimens examined The juvenal-plumaged bird differs in being washed with colder brown overall, particular- Measurements of the holotype are taken from Berlioz (1938), and are likely not to have been measured in the same way as the other specimens included here See section on

ly on the breast, vent, and center of the back. TABLE 1. Mean ( a b Pithys castaneus Pithys castaneus Pithys albifrons Pithys albifrons Gymnopithys leucaspis Gymnopithys leucaspis Phlegopsis erythroptera Phlegopsis erythroptera Rhegmatorhina melanosticta Rhegmatorhina melanosticta Furthermore, the white of the juvenile's face Pithys castaneus WILSON BULLETIN Thursday Jan 05 2006 04:24 PM wils 118_103 Mp_17 Allen Press • DTPro System GALLEY File # 03TQ

Lane et al. • REDISCOVERY OF WHITE-MASKED ANTBIRD 17

TABLE 2. Number of individuals per species attending army ant swarms (Eciton burchelli and Labidus praedator) with Pithys castaneus, Departmento Loreto, Peru, July 2001. Columns represent individual swarms. Only swarms observed for Ͼ15 min were included.

Date (ant swarma)

4 July 6 July 6 July 8 July 10 July 11 July 12 July 14 July 17 July (E) (E) (E) (E) (L) (E) (E) (L) (E) Pithys castaneus 243311443 Pithys albifrons 3 5 ÐÐÐÐÐÐÐ Phlegopsis erythroptera Ð 2 ÐÐÐÐÐÐÐ Gymnopithys leucaspis 5422Ð3244 Hylophylax poecilinota Ð2211ÐÐÐÐ Percnostola arenarum 1Ð1ÐÐÐ1 1 2 Dendrocolaptes certhia 1 3 ÐÐÐÐÐÐÐ Dendrocincla merula ÐÐÐÐÐÐÐ 1 1 Xiphorhynchus ocellatus 22ÐÐÐ1Ð11 Deconychura longicauda 1 ÐÐÐÐÐÐÐÐ

a E ϭ Eciton burchelli,Lϭ Labidus praedator.

was restricted to the area between the eye and were con®dent in labeling P. castaneus a pro- gape and a longitudinal line along the center fessional army ant-follower (sensu Willis of the throat. This specimen's dark head mark- 1967). We never saw it foraging away from ings were more extensive than those on de®n- army ant swarms and observed it attending itive-plumaged birds, and they were a duller, swarms of two army ant species: Eciton bur- sooty, dark brown (see frontispiece). chelli and Labidus praedator. For at least 12± Soft-part colors were relatively uniform 15 min on 8 July, JAA observed a single in- across most specimens. The irides were brown dividual of P. castaneus with a female Scale- or dark brown (all soft part colors taken from backed Antbird (Hylophylax poecilinota) fol- tag data recorded at time of preparation) in lowing a swarm of L. praedator ants that oc- nine specimens with adult characters, dark cupied less than 10 m2 of the forest ¯oor. The gray-brown in the three specimens with ®rst- bird's behavior was similar to that of others basic characters, and dark gray in the juvenile. observed following swarms of E. burchelli. Thus, iris color evidently changes from gray Both the P. castaneus and the H. poecilinota to dark brown as an individual ages. In all individual left the swarm for 3±4 min, only to specimens, the maxilla was blackish-slate return later. Also observed attending swarms with a silvery-white tomium, the latter con- of L. praedator (although independent of the stricted at mid-bill in some individuals. Man- above observation) were Allpahuayo Antbirds dible coloration varied more. Most adults had (Percnostola arenarum), a species previously a mostly silvery-white tomium with blackish- unknown as an ant-follower (Isler et al. 2001, slate color on the gonys and base of the man- Zimmer and Isler 2003), and Bicolored Ant- dible (except the tomium). Approximately the birds (Gymnopithys leucaspis). On four oc- distal half of the juvenile's bill was silvery- casions on different days, we observed a sin- white, and the mouth interior was dark gray. gle individual of P. castaneus quietly passing The tarsus color of adult individuals was through the forest without foraging, suggest- brownish-orange or ochre-orange; the juve- ing movement between ant swarms or be- nile's tarsi were dirty yellow with a gray tinge. tween an ant swarm and a nest (Willis 1981). The toes were dirty yellow, pale orange or dull In Table 2, we present the attendance of reg- saffron yellow; the claws of the juvenile bird ular ant-following species observed at swarms were gray. at the Morona site. Behavioral observations.ÐOur initial ob- Most often, P. castaneus was observed at servations of P. castaneus were made by TVH or near the broad front of a moving ant col- and DFL at a swarm of Eciton burchelli army umn. Individuals tended to perch Յ0.5 m ants on 4 July 2001, when the ®rst specimens above ground and frequently dropped to the were collected. Based on our observations, we forest ¯oor to investigate leaf litter or capture WILSON BULLETIN Thursday Jan 05 2006 04:24 PM wils 118_103 Mp_18 • Allen Press DTPro System GALLEY File # 03TQ

18 THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 118, No. 1, March 2006

arthropods. Birds often were observed attend- nance hierarchy among the attendant species ing a swarm for 5 to 15 min at a time and (see Willis 1967, 1981). From our observa- then leaving the swarm (at least once while tions, we concluded that the dominance hier- carrying a food item) for roughly equal peri- archy (from most to least dominant) was Phle- ods of time. On at least one such occasion, a gopsis erythroptera, Pithys castaneus, and G. pair of P. castaneus was observed joining a leucaspis. Other swarm-attending antbirds, in- family group of G. leucaspis moving between cluding Pithys albifrons, noticeably avoided what appeared to be two column heads (about the leading edge of the swarm when any of 30 m apart) of a single E. burchelli ant swarm. the other professional ant-followers were pre- Willis (1981) reported similar behavior for P. sent. Our observations of the last species albifrons. On another occasion, a single indi- agree with those of Willis (1981), who also vidual was seen moving around a standing termed P. albifrons a subordinate ant swarm hollow tree in which a swarm of E. burchelli attendant. Since the dominance hierarchy sug- had bivouacked the previous evening, but had gested above has a positive correlation to not yet started its morning activity. overall body size, we suggest that size may be Most of the professional ant-following the ultimate cause (or, alternatively, a proxi- thamnophilids at the Morona site regularly mate causeÐi.e., a source of maintenance) of made exaggerated tail ``pounding'' or ``wag- the hierarchy (see Table 1). ging'' movements (terms following Zimmer Voice.ÐWe recorded at least seven distinct and Isler 2003) while foraging at ant swarms, vocalizations from P. castaneus (Fig. 2), in- especially upon returning to a perch after cluding a mewed whistle that rises in frequen- pouncing on a prey item, or when agitated by cy (Fig. 2A). This is a single note often given the presence of an observer. P. castaneus was quietly, although occasionally it can be quite not observed regularly using any such tail loud, and we suspect represents the species' movement. Only once or twice did we notice ``loudsong'' (such as it is). To our knowledge, an individual pound its tail, usually after a P. albifrons does not give a true loudsong pouncing attack on prey; the tail movement (sensu Willis 1967, Isler et al. 1998, Isler and was made once and not repeated. By contrast, Whitney 2002, Zimmer and Isler 2003) as do DFL noted that the G. leucaspis almost con- most other thamnophilids. However, the spe- stantly wagged their tails laterally, although cies is known to produce a vocalization sim- this contrasts with the published observations ilar to that described above for P. castaneus: of others (e.g., Zimmer and Isler 2003). In ad- a rarely heard, weak, mewing whistled vocal- dition, DFL observed both P. albifrons and ization that falls in frequency and is suspected the Reddish-winged Bare-eye (Phlegopsis er- to serve as a song (Willis 1981, Isler and ythroptera) regularly pounding their tails Whitney 2002; Fig. 2B). The whistled notes downward (also see Willis 1981, 1984; Zim- of the loudsong of P. castaneus appear to be mer and Isler 2003). We were unable to de- punctuated by occasional quiet, chiming notes termine whether such tail movements are in- (Fig. 2C), perhaps an integral part of the loud- tended as a form of inter- or intraspeci®c song. Song intervals can be as short as 2 sec ``body language'' among swarm attendants, as but often are longer. a sign of agitation, or as a form of ¯ushing P. castaneus also produced two vocaliza- insect prey. Nevertheless, the relative lack of tions when alarmed or when agitated by play- such tail-moving behavior in P. castaneus back of what we believed was the species' seems noteworthy. Willis (1968) reports that song (see below). These notes of agitation the monotypic genus Skutchia also lacks ste- were interspersed with sharp chattered ``chit!'' reotypic tail-moving behavior, but other ob- calls (Fig. 2D), similar to the ``chip'' calls de- servers contest this (B. M. Whitney pers. scribed for P. albifrons by Willis (1981). An- comm.). other vocalization given by agitated birds was In our observations of ant-following birds a louder, higher-pitched ``chirr,'' with the in- at the Morona site (Table 2), we noted several dividual notes more distinct (Fig. 2E) than in occurrences of one ant-following species sup- the undisturbed chirr call (see below). Occa- planting another near the leading edges of ant sionally, the agitated chirr commenced with a swarms and took this to represent a domi- chit note (Fig. 2F). While giving these vocal- WILSON BULLETIN Thursday Jan 05 2006 04:24 PM wils 118_103 Mp_19 Allen Press • DTPro System GALLEY File # 03TQ

Lane et al. • REDISCOVERY OF WHITE-MASKED ANTBIRD 19

FIG. 2. Sound spectrograms of antbird vocalizations. Unless otherwise noted, all recordings were made by D. F. Lane at our RõÂo Morona locality, Departmento Loreto, Peru, July 2001. (A) ``Song'' of Pithys castaneus. (B) ``Song'' of Pithys albifrons (T. A. Parker, III, and G. F. Budney, from Isler and Whitney 2002). (C) ``Chime'' of Pithys castaneus. (D) ``Chit'' of Pithys castaneus. (E) Agitated ``Chirr'' of Pithys castaneus. (F) ``Chit-chirr'' of Pithys castaneus. (G) ``Mew'' of Pithys castaneus (J. Alvarez A.). (H) ``Chirr'' of Pithys castaneus. (I) ``Chirr'' of Pithys albifrons. (J) ``Chirr'' of Gymnopithys leucaspis. (K) ``Chirr'' of Phlegopsis erythroptera.

izations of agitation, one male (sex con®rmed ids when attending ant swarms, and suspected by collection), was observed perched on a to be a means of maintaining individual for- horizontal branch at the edge of a treefall gap aging space at the swarm (Willis 1967; M. L. about 2 m above the ground. This was the Isler in litt.). When the chirr of P. castaneus highest we ever observed the species to perch, was heard simultaneously with those of most and was likely an agitation response to play- of the other species of professional ant-fol- back of the song. On one occasion, a distinct, lowers at a swarm, it sounded generally loud- quiet, mewing ``eaaah'' call was given by two er, of lower overall frequency, and descended individuals while close to one another; we in- less obviously (see Fig. 2H±2K). Only the terpret this as some sort of contact call or chirr call of Phlegopsis erythroptera (Fig. 2K) ``softsong'' within the pair (Fig. 2G). reaches a frequency as low as that of Pithys The most common vocalization was a call castaneus, but the former can be distinguished given by individuals while foraging at ant easily by a higher, more metallic introductory swarms. This was a deep chirr call (terms fol- sound and a more sharply descending com- lowing Willis 1967, Zimmer and Isler 2003; ponent. The chirr call of Phlegopsis erythrop- Fig. 2H), similar to vocalizations given by tera was louder than that of Pithys castaneus most professional ant-following thamnophil- on occasion, but this appeared to be in¯u- WILSON BULLETIN Thursday Jan 05 2006 04:24 PM wils 118_103 Mp_20 • Allen Press DTPro System GALLEY File # 03TQ

20 THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 118, No. 1, March 2006

enced by emotional state and was not always explained by the possible habitat specializa- the case. tion of P. castaneus. Playback experiments using recordings of Potential distribution of Pithys castaneus.Ð the suspected song elicited varying reactions Landsat imagery, complemented with infor- from individuals: some responded immediate- mation from Instituto de Investigaciones de la ly, giving agitated calls and posing on exposed AmazonõÂa Peruana personnel and local peo- perches that were higher than typical perches ple, shows what we interpret to be fairly large (see above), while others approached silently blocks of varillal forest embedded within a to investigate. On two occasions, individuals quadrangle formed by the RõÂo MaranÄon to the approached only after 2±3 min of playback. south, the RõÂo Morona to the east, the RõÂo Playback of chirr calls resulted in a quiet, cu- Mayuriaga to the north, and the Cordillera rious approach at best. CampanquõÂs to the west. Besides this area, P. castaneus populations are likely to occur in DISCUSSION similar forest along the RõÂo Pastaza in Loreto and probably into Ecuador. At present, we Taxonomic status of the species.ÐWhereas have no information about the existence of the generic allocation of Pithys castaneus has varillal forest at the latter sites. However, been considered dubious, we believe that phe- some indicator species of varillal forest have notypic characters such as the species' song- been found along the upper RõÂo Pastaza in Ec- like vocalization, its bold chestnut plumage, uador (e.g., Pompadour Cotinga, Xipholena black hood and white face, and its saffron- punicea, and Red-fan Parrot, Deroptyus accip- yellow legs all suggest a close relationship itrinus; Ridgely and Green®eld 2001a), sug- with P. albifrons. Furthermore, R. T. Brum- gesting that the area probably supports varillal ®eld and J. G. Tello (unpubl. data) have been forest habitat. We suspect that once such for- building a molecular phylogeny of the Tham- ests along the upper RõÂo Pastaza are located nophilidae, and have found P. castaneus and and surveyed, the mystery of the true position P. albifrons to be sister taxa. of the ``Andoas'' collecting locality ®nally Potential habitat specialization.ÐBased on will be unraveled. our observations, we suspect that P. castaneus Conservation.ÐThe west bank of the RõÂo is restricted to varillal forests. We should Morona, including the areas of varillal forest note, however, that we observed and mist-net- where our work was conducted, are part of the ted P. castaneus individuals that had followed recently created Zona Reservada Santiago Co- ant swarms from varillal into varzea forest maina, created in 1999. According to Peruvian immediately adjacent to our campsite, and legislation, its new status is temporary, but twice we recorded individuals on richer, hilly supposedly, it will be ranked as a de®nitive terra ®rme forest within 300 m of typical var- conservation unit in the future (National Park, illal habitat. We never encountered Hairy- National Reserve, National Sanctuary, or crested Antbird (Rhegmatorhina melanosticta) Communal Reserve). However, local leaders at the Morona site and wonder whether it may of the Federacion de Comunidades IndõÂgenas be replaced by the similarly sized P. casta- del Rio Morona informed us that they strongly neus (see Table 1) in the region or (more like- oppose the creation of a reserve and will ®ght ly) habitat. We can ®nd no evidence that R. to prevent this action. melanosticta inhabits the region between the A branch of the North-Peruvian oil pipeline rios Santiago and Pastaza, but it is quite pos- that transports oil from the upper RõÂo Pastaza sible that this is due to poor sampling as it is passes through a large portion of varillal for- to true absence. If R. melanosticta competi- est as it crosses the RõÂo Mayuriaga on its way tively excludes P. castaneus outside the Mo- to the RõÂo MaranÄon. At present, this has meant rona-Pastaza varillal forest, this may explain the destruction of only a 50-m-wide swath of the restricted distribution of the latter species. forest along the pipeline. However, an oil spill Furthermore, if varillal forest habitat was not could have drastic consequences for this rath- included in the searches conducted by Willis er delicate habitat, particularly with its ¯at ter- and the ANSP expedition along the Pastaza, rain and poor drainage. Furthermore, the pipe- their failure to encounter the species may be line itself could represent a potential dispersal WILSON BULLETIN Thursday Jan 05 2006 04:24 PM wils 118_103 Mp_21 Allen Press • DTPro System GALLEY File # 03TQ

Lane et al. • REDISCOVERY OF WHITE-MASKED ANTBIRD 21

barrier for P. castaneus. It is also worth men- ACKNOWLEDGMENTS tioning that there are several plans to connect Ecuador's Amazonian road network to the RõÂo We thank J. P. O'Neill as the initiator and organizer of the 2001 expedition. Funding for the 2001 expedi- MaranÄoÂn. Anecdotal evidence suggests that tion was received from the Coypu Foundation and a many bird species of interior forest understory donation from the late R. B. Wallace. Additional fund- are averse to crossing large openings or other ing was provided to JAA by a Fulbright Scholarship. similar breaks, such as rivers or roads (Zim- Permits for ®eldwork were granted by INRENA, and mer and Isler 2003). Thus, gaps such as those we particularly appreciate the efforts of M. Prieto C. associated with roads and pipelines may pose and R. Acero V. of that institution. D. Huachaca, M. SaÂnchez S., A. Urbay T., M. Pizango, M. Tenazoa, H. barriers to gene ¯ow in populations of these Pizango, F. Salazar, and R. Sandoval all provided lo- understory species. gistical support in the ®eld. M. L. and P. R. Isler gra- Population estimate.ÐDuring our stay we ciously allowed us access to their data and recording surveyed about 8 km2 of white-sand forests collections, and freely provided the ®ne maps and and encountered between six and eight differ- sonograms for our ®gures. M. Levy, J. Nilsson, M. ent army ant swarms of E. burchelli and two Sokol, and B. Walker all related information from their visits to the Morona site. T. Mark provided us with his of L. praedator. Based on our extrapolations, Andoas manuscript and he and J. W. Fitzpatrick pro- we estimate the number of P. castaneus to be vided information and photos of the holotype at the between 18 and 26 individuals in the area we Paris Museum. L. B. McQueen produced the illustra- surveyed. If we consider the immediate area tion that allowed us to recognize Pithys castaneus (the Morona-Santiago inter¯uvium) covered while in the ®eld. T. S. Schulenberg provided us with with varillal, then the population estimate of rare reprints and data collected on Peruvian antbirds. P. castaneus would be ϳ1,300±2,500 individ- I. Franke J. kindly allowed us access to the ornitho- logical collection in her care at MUSM, and assisted uals. Prior to our rediscovery of P. castaneus, us in trying to ®nd more details of the two ``mystery'' the species was considered to be rare, with a Pithys castaneus specimens there. This manuscript very restricted global distribution, and prob- bene®ted from comments by M. L. and P. R. Isler, J. ably threatened (Bibby 1992, Statters®eld and V. Remsen, Jr., T. S. Schulenberg, B. Walker, B. M. Capper 2000). Considering the population es- Whitney, K. J. Zimmer, and two anonymous reviewers. timates and the potential threats presented here, we recommend changing the species' LITERATURE CITED status from Data De®cient to Vulnerable, ac- ALVAREZ A., J. AND B. M. WHITNEY. 2001. A new cording to the ranking criteria presented in Zimmerius tyrannulet (Aves: Tyrannidae) from Statters®eld and Capper (2000). If a road or white sand forests of northern Amazonian Peru. any other invasive construction project threat- Wilson Bulletin 113:1±9. ens the white-sand forests between the rõÂos ALVAREZ A., J. AND B. M. WHITNEY. 2003. New dis- Morona and Santiago, then the species' status tributional records of birds from white-sand for- should be upgraded to a category of higher ests of the northern Peruvian Amazon, with im- plications for biogeography of northern South risk. America. Condor 105:552±566. Since our rediscovery of P. castaneus in ANDERSON, A. B. 1981. White-sand vegetation of Bra- July 2001, and our discovery of the two Tre- zilian Amazonia. Biotropica 13:199±210. neman specimens in MUSM, we have been BERLIOZ, J. 1938. Pithys castanea, sp. nov. Bulletin of informed of two subsequent observations of the British Ornithologists' Club 58:90±91. P. castaneus by colleagues who visited our BERLIOZ, J. 1948. Note critique sur le genre Pithys Vieillot (FormicariideÂs). L'Oiseau et la Revue Morona site. Observers visited the site 22±24 FrancËaise d'Ornithologie 18:1±4. [in French] June 2002 and 24 May 2003 (M. Levy, J. BIBBY, C. J. 1992. Putting Biodiversity on the map: Nilsson, M. Sokol, and B. Walker pers. priority areas for conservation. International comm.). Both parties saw the species, but the Council for Bird Preservation, Girton, Cambridge, 2002 observation was of multiple individuals United Kingdom. and the observers regarded the species as CHARIF, R. A., S. MITCHELL, AND C. W. CLARK. 1995. ``one of the most common birds'' at the site. Canary 1.2. Cornell Laboratory of Ornithology, Ithaca, New York. During the 2003 visit, however, only one in- COLLAR, N. J., L. P. GONZAGA,N.KRABBE,A.MAD- dividual was observed, possibly because RONÄ O NIETO,L.J.NARANJO,T.A.PARKER, III, AND swarms of army ant were not easily encoun- D. C. WEGE. 1992. Threatened birds of the Amer- tered then (an artifact of the season?). icas: the ICBP/IUCN Red Data Book, third ed., WILSON BULLETIN Thursday Jan 05 2006 04:24 PM wils 118_103 Mp_22 • Allen Press DTPro System GALLEY File # 03TQ

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