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NATURAL
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31

FIELDIANA ZOOLOGY

Published by
CHICAGO NATURAL HISTORY MUSEUM

Volume 31 July 29, 1949 No. 31

A NEW ANT-THRUSH FROM
BRITISH GUIANA

Emmet R. Blake
Associate Curator, Division of Birds

In 1938 I made a collection of birds for Chicago Natural History
Museum in the Acary Mountains and adjacent lowlands of southern
British Guiana. Two of the novelties in the collection, a toucanet
(Aulacorhynchus derbianus osgoodi) and a woodpecker (Piculus
rubiginosus nigriceps), have been described elsewhere (Blake, Field
Mus. Nat. Hist., Zool. Ser., 24, No. 20, 1941, pp. 227-232). The
presence of these birds in a region that does not exceed 4,000 feet
in altitude, and averages much less, evidently constitutes an extreme
projection of the rich subtropical fauna previously identified with
Mount Roraima, Mount Auyan-tepui, and associated highlands of
southeastern Venezuela.

Many of the 150 forms in the collection represent considerable
extensions of range, either from the east or from the west. A notable
example is that of the Andean ant-thrush, Terenura callinota, an
eastern race of which is described below preparatory to the publica-
tion of a general report on the bird fauna of the Acary Mountains.

I am indebted to Dr. John T. Zimmer of the American Museum
of Natural History and to Dr. Arthur Twomey of the Carnegie
Museum for the loan of comparative material.

Capitalized names of all colors used in this paper are from
Ridgway's Color Standards and Nomenclature, 1912.

Terenura callinota guianensis subsp. nov.

Type. Chicago Natural History Museum No. 120311, from
Boundary Camp, head of Itabu Creek, Acary Mountains, British
Guiana. Altitude 2,000 feet. Male. Collected September 30,
1938, by Emmet R. Blake. Orig. No. 7403.

Diagnosis. Similar to T. c. callinota (Sclater) of Colombia, but
the rump and lower back notably darker and richer, being Claret

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268 FIELDIANA: ZOOLOGY, VOLUME 31

Brown rather than Sanford's Brown or Orange Rufous. Bend of
the wing and adjacent coverts slightly darker and more intensely
yellow than in callinota.

Range. Known only from the type locality.

Remarks. This surprising addition to the Guianan fauna con-
stitutes the first record of the species east of the Andes and represents
a minimum range extension of approximately 1,200 miles. The
British Guiana specimen was originally sexed as a female, but its
black pileum and fully developed yellow shoulder patches un-
questionably mark it as a male, although evidently in subadult
plumage, as indicated both by the absence of dorsal streaks and by
the intermediate appearance of the greater and middle coverts in
which the black areas are only partially developed. The distinct
color tone of the rump and lower back is clearly of geographical
significance, however, since it is not duplicated in either sex of
T. c. callinota.

As is well known, the faunas of mountainous areas as far east-
ward as Mount Roraima contain elements having Andean affinities.
The discovery of a race of callinota in the Acary Mountains, east
of Essequibo River drainage, represents a considerable extension of
the Andean influence a circumstance of some significance in view
of the discovery in the same area (Blake, MS.) of a typical example
of Contopus nigrescens canescens, previously known only from Peru.

SPECIMENS EXAMINED

T. c. callinota. Colombia: Bitaco Valley, two males; La Cumbre,
one male, one female; Aguadita, one female. Ecuador: Sabanilla,
one female; Papallacta, one male.

T. c. guianensis. British Guiana: Acary Mountains, one male.