LIBRARY OF THE

UNIVERSITY OF ILLINOIS

AT URBANA-CHAMPAIGN

590.5
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V.39
cop. 3

NATURAL HISTORY,
SURVEY

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f^ FIELDIANA ZOOLOGY

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CHICAGO NATURAL HISTORY MUSEUM

Volume 39 June 26, 1957 No. 7

A NEW SPECIES OF ANT-THRUSH
FROM PERU

Emmet R, Blake

Curator, Division of Birds

A small collection of birds made in the Department of Madre de
Dios, southeastern Peru, by Celestino Kalinowski, contains a single
specimen of Formicarius that is conspicuously different from any
known relative and apparently represents a distinct new species as
described below.

All measurements are in millimeters. The wings are measured
flat. Names of colors when capitalized indicate direct comparison
with Ridgway's Color Standards and Color Nomenclature (1912 ed.).

Formicarius rufifrons, new species

Type. Chicago Natural History Museum no. 222919 from Boca
Colorado, Lat. 12 30' S., Long. 70 25' W., Madre de Dios, Peru.
Adult female, collected October 22, 1954, by Celestino Kalinowski.

Diagnosis. Nearest to Formicarius a. analis of Amazonian Peru,
adjacent parts of Brazil, and northeastern Bolivia, but forehead
bright rufous, contrasting sharply with feathers of crown; loral area
wholly black without white spot; throat and malar region dark
sooty gray (not black) like breast; axillaries, under wing coverts and
inner edges of remiges uniform bright cinnamon, this progressing on
successive secondaries and extending almost to the tips of the inner-
most; under tail coverts dull reddish brown, showing slight contrast
with adjacent under parts.

Range. Known only from the type specimen, collected in Madre
de Dios, Peru, at the junction of Rio Colorado and Rio Manu
(right bank) about halfway between the villages of Manu and
Madre de Dios.

Description of type. Forehead and feathers above nostrils
Orange Rufous X Cinnamon-Rufous; lores, eyelids (except posteri-

Library of Congress catalog card number: 57-12367

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52 FIELDIANA: ZOOLOGY, VOLUME 39

orly), and supramalar region black; crown, hindneck, back, and
wing coverts Raw Umber X Medal Bronze, becoming more rufescent
posteriorly; rump and upper tail coverts nearest reddish Vandyke
Brown; rectrices black, the outer webs edged with brownish olive
basally. Throat, malar region, and breast uniform sooty gray,
nearest Dark Mouse Gray, this becoming conspicuously paler on
abdomen. Sides and flanks dull brownish olive; crissum brownish
olive faintly tinged with chestnut, but duller than upper tail coverts.
Axillaries, under wing coverts, and inner webs of remiges (basally)
immaculate Apricot Orange X Apricot Buff, this lengthening on the
edges of successive secondaries and approaching the tips of the
innermost. Bill blackish, palest below; legs brownish horn. Wing,
84; tail, 62; exposed culmen, 17; culmen from base, 21; tarsus, 34;
middle toe without claw, 20.

Remarks. Sexes presumably similar, as with other species of the
genus. The color pattern of rufifrons differs conspicuously from that
of any known relative and at present its affinities are uncertain.
In general there is perhaps greatest agreement with F. analis, of
which Chicago Natural History Museum has a typical example
of the nominate race taken at Boca Colorado, the type locality of
rufifrons. In some respects the similarity is most pronounced in
geographically distant races of analis, as witness the close agreement
of F. rufifrons and certain examples of F. a. umhrosus in dullness
of the crissum.

A closer relationship between rufifrons and F. colma possibly is
indicated by the presence in both of rufous on the head, and by the
absence of a white loral spot. A race of the latter, nigrifrons, occurs
in Peru south to the mouth of the Urubamba and presumably is
sympatric with rufifrons. In both, the throat and breast are con-
colorous, conspicuously black in one and sooty gray in the other,
but this is of doubtful significance. In any case, rufifrons is unique
among its relatives in having immaculate cinnamon axillaries and
under wing coverts.

The proportions of rufifrons (see measurements above) and its
possession of erect feathers growing virtually to the anterior end of
the nasal fossae unexpectedly agree with the generic characters
generally assigned to Chamaeza, all species of which are conspicu-
ously different from rufifrons in color pattern. However, analysis
of the measurements of both Chamaeza and Formicarius reveals
exceptions to Ridgway's concept (Bull. U. S. Nat. Mus., 50, pt. 1,
p. 15, key) of their mutually exclusive proportions, and some speci-

-TJif, 7 BLAKE: NEW ANT-THRUSH FROM PERU 53

mens of each now before me are quite similar in respect to the
extent of feathering above the nostrils. It follows that if both
genera are to be maintained, as seems proper in the light of present
knowledge, their characters must be based on plumage patterns as
well as on relative proportions. A possible supplementary character,
hitherto overlooked and brought to my attention by Dr. Austin L.
Rand, is the relative curvature of the hallux claw. This is almost
straight in Formicarius (including rufifrons) and decidedly curved
in Chamaeza.

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