FAUNA PARAGUAY BELLBIRD JOURNAL MORPHOMETRICS OF CHACO BIRDS

Resumen
Peso y datos biométricos de aves del Chaco Seco de Parque Nacional Teniente Agripino Enciso, Departamento Boquerón, Paraguay. - Se disponen de datos biométricos de 211 individuos de 38 especies de aves del Chaco Seco del Parque Nacional Teniente Agripino Enciso National Park en el noroeste del Paraguay.

Abstract
Biometric data are provided for 211 individuals of 38 species from the Dry Chaco of Teniente Agripino Enciso National Park in north-western Paraguay.

Key Words: Weight, Measurements, Paraguay, Chaco, Birds, Enciso

INTRODUCTION
Since the publication by Whittle (1927) calling for the publication of more biometric data for birds, very little has been forthcoming on Neotropical birds. The only published data for Paraguayan birds is based on a small sample of just 17 species documented by Peris (1990) for the Humid Chaco. Here we present the first published biometric data on live birds from the Dry Chaco of Paraguay, covering a total of 211 individuals of 38 species measured during 2-28 July 2006 (Smith et al 2006).
Fieldwork took place in Teniente Agripino Enciso National Park (21º05´S, 61º08´W) in the High Chaco at approximately km660 of the Ruta Trans-Chaco. “Enciso” is 40,000ha reserve consisting of relatively uniform, xerophytic, spiny Chaco forest. A single walking trail, the “Sendero Trenchera” runs for approximately 2km in a loop from the administration block and netting was performed along the this trail. A small watering hole, artificially maintained, acts as a magnet for birds and other animals in this exceptionally dry environment.

METHODS
   Birds were captured using 12 Japanese mist-nets with a total length of 96m and a total area of 192m². Netting was performed from 6am until 6pm every day during the study period, a total of 324 net hours. Nets were set at a maximum height of 2m and given the stunted vegetation in the Dry Chaco there was limited bias in the species captured. Captured birds were immediately released after measurement, moult and weight data had been taken. Measurements were taken according to Svensson (1984). The one exception to these rules was the use of the minimum chord wing measurement, which does not involve the flattening of the wing against the ruler, measuring the wing parallel to the body from the wing bend to the tip of the longest primary. Weights were taken using 100g and 1kg Pessola spring balances. All English and scientific names follow FAUNA Paraguay (2008).

RESULTS
   Each species is treated individually. The following codes are used below C = exposed culmen; B = bill length from base to tip; BD = bill depth across middle of nares; BW = bill width across middle of nares; HB = head + bill length; T = tarsus; W = minimum chord wing measurement; Tl = Tail; Wt = mass in grams; N = number of individuals captured. The mean measurement is given followed by the standard deviation in parentheses. In sexually dimorphic species separate measurements are given for males and females. All measurements are given in mm and the mass in grams. Species considered endemic to the Chaco biome are marked (CH) (Clay & del Castillo 2004). Data for a total of 5 Chaco endemic species is presented. Taxonomic notes are included where relevant.

Quebracho Crested-tinamou Eudromia formosa (Tinamidae):
N = 1 ad female. C = 25; B = 37; BD = 8.50; BW = 8.50; HB = 60; T = 55; W = 210. Individual found dead with egg-extruded from cloaca see Smith, Pearman & Betuel in press. Paraguayan birds are sometimes referred to the subspecies E.f.mira but the evidence for separation is weak and the species might best be considered monotypic (Blake 1977, Cabot 1992, Davies 2002)
   Rufous-thighed Hawk Accipiter erythronemius (Accipitridae):
N = 1 ad. C = 11 including cere; B = 14.50; BD = 10; BW = 6; HB = 38; T = 43.50; W = 157; Tl = 132; Wt = 86. Measurements are consistent with a small male (Ferguson-Lees & Christie 2001, Brown & Amadon 1989). This species was treated as a subspecies of A.striatus by both these authors and Short (1976) who misspells it as A.s.erythrocnemius. The species was split by Sibley & Monroe (1990), and followed by Ridgely & Greenfield (2001) amongst others. The SACC Checklist committee continues to list this form as a subspecies of A.striatus in view of the lack of published evidence, but recognizes that the split “is almost certainly good”.
   Roadside Hawk Rupornis magnirostris (Accipitridae):
N = 2 ad unsexed. C = 27.25 (+/-   0.35) including cere; B = 27.50 (+/-   2.12); BD = 14.50 (+/-   2.12); BW = 12.50 (+/-   0.71); HB = 62 (+/-   0); T = 62 (+/-   0); W = 270 (+/-   14.14); Tl = 160 (+/-   0). Plumage and measurements consistent with the subspecies saturatus (Blake 1977, Ferguson-Lees & Christie 2001).
   Picui Ground-dove Columbina picui (Columbidae):
N = 4 ad unsexed. C = 13.25 (+/-   1.26); B = 15.25 (+/-   1.55); BD = 4.25 (+/-   0.50); BW = 4.13 (+/-   0.25); HB = 33.63 (+/-   1.49); T = 17.13 (+/-   1.84); W = 88.25 (+/-   1.19); Tl = 78.38 (+/-   1.49); Wt = 46.50 (+/-   3.32).
N = 2 ad male. C = 14.25 (+/- 0.35); B = 16.50 (+/- 0); BD = 3.75 (+/- 0.35); BW = 3.50 (+/- 0.71); HB = 35 (+/- 0); T = 15.50 (+/- 0.71); W = 89 (+/- 4.24); Tl = 80.50 (+/- 7.78); Wt = 46 (+/- 0).
N = 5 ad female. C = 13.50 (+/- 0.87); B = 16.90 (+/- 1.24); BD = 4 (+/- 0); BW = 3.80 (+/- 0.27); HB = 34.40 (+/- 0.96); T = 17.20 (+/- 1.96); W = 87.60 (+/- 1.34); Tl = 77.70 (+/- 1.52); Wt = 47.50 (+/- 2.74).
N = 1 imm unsexed. C = 12; B = 16; BD = 3.50; BW = 4; HB = 35; T = 15.50; W = 86; Tl = 75.50; Wt = 39.
The species is represented in Paraguay by the widespread subspecies C.p.picui (Gibbs, Barnes & Cox 2001).
   Monk Parakeet Myiopsitta monachus (Psittacidae):
N = 1 ad unsexed. C = 18; B = 18; BD = 19; BW = 12; HB = 37.50; T = 19; W = 135.50; Tl = 138. There is confusion as to the subspecific identity of the birds inhabiting the Paraguayan Chaco. Juniper & Parr (1998) give the range of M.m.calita as extending from Santa Cruz, Bolivia, through Paraguay “where range unclear” to Jujuy and Rio Negro in Argentina, and that of M.m.cotorra as “the Bolivian and Paraguayan Chaco south along Rio Paraguay and Paraná” adding that “range in Bolivia and Paraguay in respect of reported range of calita unclear”. However Forshaw (1989) lists calita as occurring in “western Argentina from Salta ….South to Mendoza and La Pampa” with no mention of that subspecies occurring in Paraguay or Bolivia. Despite the supposedly brighter upperparts and less yellowish abdomen of cotorra when compared to calita Short (1976) could find no difference between the two and considered calita to be a synonym of cotorra.
   Glittering-bellied Emerald Chlorostilbon lucidus (Trochilidae):
N = 1 ad male. C = 18; B = 18.50; BD = 2; BW = 4; HB = 30; T = 4.50; W = 49; Tl = 31; Wt = 3.
N = 1 ad female. C = 19; B = 20.50; BD = 2; BW = 2.50; HB = 33; T = 4.50; W = 49; Tl = 31.50; Wt = 4.
Formerly referred to as C.aureoventris, though this nomenclatural error was corrected by Pacheco & Whitney (2006).
   Green-barred Flicker Colaptes melanochloros (Picidae):
N = 1 ad male. C = 23.50; B = 29; BD = 10; BW = 10; HB = 71.50; T = 27.50; W = 146; Tl = 96. Specimen referable to C.m.nigroviridis according to description and measurements given in Short (1972).
   Great Antshrike Taraba major (Thamnophilidae):
N = 1 ad male. C = 23; B = 28; BD = 9; BW = 6; HB = 49; T = 35; W = 93.50; Tl = 87.50.
N = 3 ad female. C = 22.50 (+/- 0.87); B = 28 (+/- 0); BD = 9 (+/- 0); BW = 6.50 (+/- 0.50); HB = 48.17 (+/- 0.29); T = 34 (+/- 1); W = 87.67 (+/- 1.04); Tl = 87.33 (+/- 0.58); Wt = 47 (+/- 2.83).
   Variable Antshrike Thamnophilus caerulescens (Thamnophilidae):
N = 1 ad male. C = 13.50; B = 17; BD = 6; BW = 6; HB = 36; T = 25; W = 66; Tl = 61; Wt = 17. Specimen referable to white-bellied subspecies T.c.paraguayensis according to description in Zimmer & Isler (2003).
   Crested Hornero Furnarius cristatus (Furnariidae) (CH):
N = 4 ad unsexed. C = 15.38 (+/- 0.95); B = 18.63 (+/- 1.11); BD = 4 (+/- 0); BW = 4 (+/- 0.41); HB = 38.13 (+/- 1.31); T = 26.75 (+/- 1.32); W = 73.75 (+/- 2.72); Tl = 60.75 (+/- 2.75); Wt = 25.33 (+/- 1.15).
Rufous Hornero Furnarius rufus (Furnariidae):
N = 4 ad unsexed. C = 18.63 (+/- 1.11); B = 25.38 (+/- 0.75); BD = 4.88 (+/- 0.25); BW = 4.63 (+/- 0.48); HB = 44.50 (+/- 1.96); T = 31 (+/- 1.83); W = 86 (+/- 9.67); Tl = 68.63 (+/- 1.70); Wt = 39.50 (+/- 2.29). These individuals were much more reddish on the nape and forehead and with a more strongly defined facial pattern than birds found in eastern Paraguay (see images www.faunaparaguay.com/furnarius_rufus.html). The throat is also much purer white resulting in the appearance of a much more boldly-marked bird. Furthermore they are consistently smaller in all measurements than birds captured in southern Paraguay. Vaurie (1980) describes variation in this species as clinal yet Clements (2000) listed five subspecies, giving only F.r.paraguayae for Paraguay. Short (1975) stated that most of the Chaco is occupied by F.r.paraguayae but makes no reference to this distinctive form in the northern Chaco. The subspecies present in Bolivia is F.r.commersoni and these birds may be referable to that form or else intergrades between it and paraguayae.
   Brown Cacholote Pseudoseisura lophotes (Furnariidae):
N = 1 ad unsexed. C = 24.50; B = 30.50; BD = 8; BW = 8; HB = 53; T = 34.50; W = 128; Tl = 112.50.
   Pale-breasted Spinetail Synallaxis albescens (Furnariidae):
N = 1 ad unsexed. C = 10; B = 13.50; BD = 4; BW = 3; HB = 30; T = 18; W = 52; Tl = 77.50; Wt = 12. Individual presumably attributable to the subspecies S.a.australis.
   Little Thornbird Phacellodomus sibilatrix (Furnariidae):
N = 2 ad unsexed. C = 12.25 (+/- 0.35); B = 16 (+/- 0); BD = 4 (+/- 0); BW = 3.50 (+/- 0); HB = 32.75 (+/- 0.35); T = 19 (+/- 0); W = 54.25 (+/- 1.06); Tl = 63 (+/- 1.41); Wt = 14.50 (+/- 0.71).
   Short-billed Canastero Asthenes baeri (Furnariidae):
N = 2 ad unsexed. C = 10.50 (+/- 0.71); B = 12 (+/- 0); BD = 3.75 (+/- 0.35); BW = 3.50 (+/- 0.71); HB = 31 (+/- 0); T = 20.75 (+/- 1.06); W = 56 (+/- 1.41); Tl = 61 (+/- 1.41); Wt = 14 (+/- 0).
   Lark-like Brushrunner Coryphistera alaudina (Furnariidae):
N = 24 ad unsexed. C = 14.79 (+/- 0.75); B = 17.85 (+/- 1.22); BD = 5.25 (+/- 0.53); BW = 4.65 (+/- 0.58); HB = 35.71 (+/- 1.50); T = 26.63 (+/- 1.45); W = 71.89 (+/- 2.35); Tl = 72.76 (+/- 4.23); Wt = 30.23 (+/- 1.09).
   Narrow-billed Woodcreeper Lepidocolaptes angustirostris (Furnariidae: Dendrocolaptinae):
N = 12 ad unsexed. C = 31.50 (+/- 1.37); B = 36.63 (+/- 1.65); BD = 5.04 (+/- 0.33); BW = 4.59 (+/- 0.51); HB = 54.75 (+/- 1.42); T = 20.08 (+/- 0.76); W = 87.25 (+/- 3.04); Tl = 73.58 (+/- 5.90); Wt = 25.80 (+/- 2.59).
   Greater Wagtail-tyrant Stigmatura budytoides (Tyrannidae):
N = 7 ad unsexed. C = 10.64 (+/- 0.63); B = 13.64 (+/- 0.56); BD = 3.36 (+/- 0.48); BW = 4.21 (+/- 0.39); HB = 30.71 (+/- 1.91); T = 21 (+/- 1.66); W = 55.71 (+/- 2.20); Tl = 73.67 (+/- 4.29); Wt = 9.75 (+/- 0.50).
The tail seems to play an important role in visual displays of this species. Within this small sample two individuals had considerably longer tails than the other birds (80 and 78mm respectively, compared to a range of 69.5-72mm for the other birds), possibly representing a sexual difference. Fitzpatrick (2004) mentions that females are slightly smaller but does not specifically mention tail length as a distinguishing character. Our measurements showed no statistically significant differences in any other measurements that we took. Further sampling including field observation and possibly molecular sexing is required to confirm or disprove this theory.
   Pearly-vented Tody-tyrant Hemitriccus margaitaceiventer (Tyrannidae):
N = 4 ad unsexed. C = 12.63 (+/- 0.85); B = 14.63 (+/- 0.95); BD = 3.40 (+/- 0.25); BW = 4.40 (+/- 0.48); HB = 30 (+/- 0.71); T = 19.63 (+/- 1.44); W = 48.13 (+/- 3.12); Tl = 44.63 (+/- 4.40); Wt = 7.50 (+/- 0.71).
   Suiriri Flycatcher Suiriri suiriri (Tyrannidae):
N = 2 ad unsexed. C = 12.75 (+/- 0.35); B = 16 (+/- 1.41); BD = 4.75 (+/- 0.35); BW = 5.75 (+/- 0.35); HB = 31.75 (+/- 0.35); T = 15.75 (+/- 2.47); W = 69 (+/- 2.82); Tl = 68 (+/- 4.24). These birds were of the white-bellied form and are referable to S.s.suiriri.
   Cinereous Tyrant Knipolegus striaticeps (Tyrannidae) (CH):
N = 1 ad male. C = 13; B = 17; BD = 4; BW = 5; HB = 33.50; T = 19.50; W = 58; Tl = 61.
N = 3 ad female. C = 12.33 (+/- 1.15); B = 15.83 (+/- 1.04); BD = 3.67 (+/- 0.29); BW = 5.17 (+/- 0.29); HB = 32.33 (+/- 0.58); T = 20 (+/- 1); W = 55.83 (+/- 1.26); Tl = 57.83 (+/- 2.25); Wt = 13 (+/- 1.41).
   White-crested Tyrannulet Serpophaga subcristata (Tyrannidae):
N = 6 ad unsexed. C = 8.50 (+/- 0.45); B = 10.42 (+/- 0.74); BD = 2.58 (+/- 0.38); BW = 3.08 (+/- 0.20); HB = 24.42 (+/- 0.58); T = 16.92 (+/- 0.58); W = 47.42 (+/- 1.36); Tl = 46.92 (+/- 1.28); Wt = 5.33 (+/- 0.41). Not mapped for the Chaco by Guyra Paraguay (2005) based on the assumption that all Chaco records applied to the cryptic Serpophaga griseicapilla (R.Clay in litt.). Our records suggest that the two species are probably widely sympatric throughout the Paraguayan Chaco as they appear to be in suitable habitat in neighbouring Argentina (Straneck 2007).
   Grey-capped Tyrannulet Serpophaga griseicapilla (Tyrannidae).
N = 7 ad unsexed. C = 8.93 (+/- 0.67); B = 10.79 (+/- 0.76); BD = 2.86 (+/- 0.24); BW = 3.36 (+/- 0.48); HB = 24.79 (+/- 0.70); T = 16.07 (+/- 0.73); W = 45.07 (+/- 1.37); Tl = 42.21 (+/- 1.47); Wt = 5.25 (+/- 0.50).
This recently redescribed taxon (Straneck 2007) has a checkered taxonomic history (Straneck 1993, Herzog & Mazar Barnett 2004). Our measurements coincide well with the measurements presented for the species in Straneck. S.griseicapilla is only reliably separated from S.subcristata in the field by its distinctive vocalizations, but inhand it is easily distinguished by the absence of black lateral coronal stripes and the absence of or greatly reduced hidden white in the crown.
   Rufous Casiornis Casiornis rufa (Tyrannidae):
N = 1 ad male. C = 20; B = 25; BD = 5.50; BW = 7.50; HB = 38; T = 19.50; W = 84.50; Tl = 75; Wt = 21.
   Masked Gnatcatcher Polioptila dumicola (Polioptilidae):
N = 2 ad male. C = 10.75 (+/- 1.06); B = 13.25 (+/- 1.06); BD = 2.25 (+/- 0.35); BW = 3.25 (+/- 0.35); HB = 27 (+/- 0); T = 17.25 (+/- 0.35); W = 52 (+/- 0.71); Tl = 57.50 (+/- 3.53).
N = 1 ad female. C = 9.50; B = 13; BD = 2; BW = 3.50; HB = 27.50; T = 16.50; W = 46; Tl = 53; Wt = 6.
   Rufous-browed Peppershrike Cyclarhis gujanensis (Vireonidae):
N = 1 ad unsexed. C = 19; B = 21; BD = 10; BW = 6; HB = 39; T = 26; W = 77; Tl = 70.50; Wt = 30.
Tropical Parula Parula pitiayumi (Parulidae):
N = 1 ad male. C = 11; B = 13; BD = 3.50; BW = 3.50; HB = 22.50; T = 18; W = 51; Tl = 40.
N = 3 ad female. C = 9.83 (+/- 0.29); B = 11.33 (+/- 1.04); BD = 3 (+/- 0); BW = 3.17 (+/- 0.29); HB = 25.83 (+/- 0.29); T = 17.33 (+/- 1.15); W = 51.50 (+/- 0.89); Tl = 41 (+/- 0); Wt = 7.33 (+/- 0.58). Consistent with the subspecies P.p.pitiayumi according to description and measurements given in Curson, Quinn & Beadle (1994).
   Lowland Hepatic-tanager Piranga flava (Cardinalidae):
N = 1 ad female. C = 17; B = 21; BD = 8.50; BW = 9; HB = 41.50; T = 25; W = 88; Tl = 77; Wt = 35.
   Golden-billed Saltator Saltator aurantiirostris (Cardinalidae):
N = 4 ad unsexed. C = 19.63 (+/- 1.18); B = 21 (+/- 0.41); BD = 12.38 (+/- 0.48); BW = 9.13 (+/- 0.63); HB = 41.75 (+/- 3.59); T = 26.50 (+/- 0.58); W = 91 (+/- 3.37); Tl = 89 (+/- 3.56); Wt = 39.50 (+/- 4.95).
N = 1 imm unsexed. C = 19; B = 20.50; BD = 12; BW = 8.50; HB = 39; T = 26; W = 89; Tl = 89; Wt = 43.
   Red-crested Finch Coryphospingus cucullatus (Emberizidae):
N = 19 ad male. C = 11.68 (+/- 0.58); B = 12.76 (+/- 0.63); BD = 6.08 (+/- 0.30); BW = 4.92 (+/- 0.61); HB = 28.53 (+/- 0.79); T = 18.53 (+/- 1.05); W = 62.61 (+/- 1.66); Tl = 60.06 (+/- 2.11); Wt = 13.75 (+/- 0.80).
N = 17 ad female. C = 9.25 (+/- 0.87); B = 12.94 (+/- 0.66); BD = 6 (+/- 0.43); BW = 4.68 (+/- 0.25); HB = 28.12 (+/- 1.47); T = 18.18 (+/- 0.88); W = 60.85 (+/- 1.18); Tl = 58.94 (+/- 2.70); Wt = 14.47 (+/- 1.03).
N = 2 imm unsexed. C = 12 (+/- 0); B = 14 (+/- 0); BD = 6.75 (+/- 0.35); BW = 5 (+/- 0); HB = 28.50 (+/- 0.71); T = 19.50 (+/- 1.41); W = 61 (+/- 1.41); Tl = 56 (+/- 1.41).
These birds are referable to C.c.fargoi
   Many-coloured Chacofinch Saltatricula multicolor (Emberizidae) (CH):
N = 22 ad unsexed. C = 12.33 (+/- 0.66); B = 13.55 (+/- 0.65); BD = 7.21 (+/- 0.58); BW = 6 (+/- 0.63); HB = 31 (+/- 1.29); T = 22.70 (+/- 1.59); W = 68.18 (+/- 1.78); Tl = 78.71 (+/- 4.42); Wt = 22 (+/- 1.53).
   Saffron Finch Sicalis flaveola (Family Emberizidae):
N = 1 ad male. C = 10; B = 11.50; BD = 6.50; BW = 5; HB = 25.50; T = 17.50; W = 67; Tl = 55; Wt = 16.
N = 1 imm. male. C = 10; B = 10; BD = 6.5; BW = 5; HB = 25; T = 15.50; W = 65; Tl = 53.50.
N = 4 ad female. C = 9.25 (+/- 0.87); B = 10.25 (+/- 0.50); BD = 6.25 (+/- 0.29); BW = 5.38 (+/- 0.25); HB = 24.50 (+/- 1.35); T = 17.38 (+/- 1.60); W = 62.75 (+/- 1.26); Tl = 47.38 (+/- 3.82); Wt = 14.25 (+/- 0.96).
Black-capped Warbling-finch Poospiza melanoleuca (Emberizidae) (CH):
N = 1 ad male. C = 10; B = 12; BD = 5; BW = 4; HB = 21.50; T = 20; W = 60; Tl = 59.
N = 4 ad female. C = 9.75 (+/- 0.65); B = 10.50 (+/- 1.08); BD = 5 (+/- 0); BW = 4.25 (+/- 0.29); HB = 24.50 (+/- 2.35); T = 18.88 (+/- 1.31); W = 55.13 (+/- 2.78); Tl = 55.63 (+/- 1.80); Wt = 10.50 (+/- 0.71).
   Black-crested Finch Lophospingus pusillus (Emberizidae):
N = 2 ad male. C = 11.50 (+/- 0.71); B = 12.50 (+/- 0.71); BD = 7 (+/- 0.71); BW = 5.25 (+/- 0.35); HB = 28.25 (+/- 0.35); T = 16.75 (+/- 1.77); W = 63.25 (+/- 1.77); Tl = 55 (+/- 1.41); Wt = 15 (+/- 0).
N = 1 imm. male. C = 11; B = 12.50; BD = 7; BW = 6; HB = 28; T = 16; W = 63; Tl = 55.
N = 12 ad female. C = 11.04 (+/- 0.45); B = 12.04 (+/- 0.40); BD = 6.71 (+/- 0.39); BW = 5.04 (+/- 0.58); HB = 27.33 (+/- 0.89); T = 17.75 (+/- 1.47); W = 60.50 (+/- 1.20); Tl = 52.82 (+/- 2.04); Wt = 14.29 (+/- 1.38).
   Rufous-collared Sparrow Zonotrichia capensis (Family Emberizidae):
N = 1 ad unsexed. C = 11; B = 13; BD = 7; BW = 6; HB = 29; T = 20.50; W = 63; Tl = 57.
   Greyish Baywing Agelaoides badius (Family Icteridae):
N = 1 ad unsexed. C = 17; B = 19; BD = 8; BW = 6; HB = 37; T = 25; W = 83; Tl = 75.50; Wt = 38. Consistent with the subspecies M.b.badius according to description and measurements given in Jaramillo & Burke (1999).
   Orange-backed Troupial Icterus croconotus (Family Icteridae):
N = 1 ad male. C = 23; B = 25; BD = 8; BW = 6; HB = 48.50; T = 27; W = 102; Tl = 113; Wt = 45.
N = 1 ad female. C = 24; B = 24.50; BD = 6.50; BW = 6; HB = 45; T = 25; W = 95; Tl = 105.50; Wt = 40.
Consistent with the subspecies I.c.stictifrons according to description and measurements given in Jaramillo & Burke (1999). The pair also showed plumage differences that are apparently not mentioned in the literature, with the female having less white on the secondaries and more extensive black on the mantle forming an almost complete band across the lower back (see images www.faunaparaguay.com/icterus_croconotus.html). Short (1976) alludes to the presence of a “narrow black band across the back” of three of the four specimens he examined from the Paraguayan Chaco (consisting of 2 females, one male and an unsexed bird), noting that the band was “discontinuous” in the other bird. Unfortunately however he does not state the sex of the bird showing the discontinuous band. Further sampling is required to determine whether or not the band represents a sexual plumage difference.
   Epaulet Oriole Icterus cayanensis (Family Icteridae):
N = 1 ad unsexed. C = 15.50; B = 18.50; BD = 5.50; BW = 5.50; HB = 37; T = 21; W = 85; Tl = 94; Wt = 28. Specimen consistent with a female of I.c.pyrrhopterus according to description and measurements given in Jaramillo & Burke (1999).
N = 1 imm. unsexed. C = 17; B = 20; BD = 5; BW = 5; HB = 38; T = 22.50; W = 85; Tl = 95; Wt = 24.

DISCUSSION
With such limited data available for Paraguay and the fact that the data that has been published was obtained in a completely different habitat type, it is difficult to draw any firm conclusions from direct comparisons. Six species captured by Peris (1990) in Departamento Presidente Hayes, in Humid Chaco were also caught by us:
   Furnarius rufus Measurements provided for 5 specimens of this species by Peris (1990) correspond well with our own findings. Unfortunately no comments were provided regarding the appearance of the birds in question and no attempts were made at subspecific designation (see comments under the species above).
   Lepidocolaptes angustirostris Mean measurements provided by Peris (1990) for six specimens are within the standard deviations found in our sample.
   Poospiza melanoleuca Peris (1990) provided measurements for a single male bird that are within the expected normal standard deviation from the measurements for our male specimen.
   Zonotrichia capensis Measurements for our single specimen are within the range provided by Peris (1990) for his sample of 13 specimens.
   Icterus cayannensis Peris (1990) provided only weight data for four unsexed specimens (30g (+/- 2). Given the sexual variation in size in Icterids it is impossible to draw any firm comparisons for unsexed material.
   Agelaoides badius The measurements of our single bird are within the ranges given for “Molothrus” badius by Peris (1990). Differences in wing measurement (Peris 89mm +/- 1.7 v 83mm) are possibly attributable to different measurement techniques used.
Given the paucity of published morphometric data, the authors would like to repeat Whittle´s (1927) call for the publication of more biometric data.

ACKNOWLEDGEMENTS
   Thanks to the forest guards at PN Tte Enciso for their hospitality and assistance during field work, especially Mario Torales and Odulio Mareco. Particular thanks to Enrique Bragayrac of the SEAM (Secretaria del Medio Ambiente) who granted us permission to work at Enciso and Alberto Yanosky of Guyra Paraguay for facilitating contacts. Hugo del Castillo and Frank Fragano assisted with logistics and Sylvia Centrón accompanied us in the field. .

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