Cercomacra and related antbirds (Aves, Formicariidae) as army ant followers.

Revta bras. Zoo!., S Paulo 2(7): 427-432

28.vi.1985

CERCOMACRA

AND RELATED ANTBIRDS (AVES, FORMICARIIDAE)

AS ARMY ANT FOLLOWERS

EDWIN O . WILLIS

ADSTRACT

Cercomacra

Schistocichla

Drymophi!a-Hypocnemis

Formi-cívora

Antbirds of

and related genera (Formicariidae) occasional1y

capture arthropods flushed by swarms of army ants in neotropical forests

(Oniki, 1972; Oniki

Willis, 1972). Here, in the twenty-first of a series of

reports on occasional ant followers, I note information on specíes of

and

The first two

genera "flick" the tai! upward, and seem related to the

group of antbirds; the last three genera "pound" the tails or "twitch" them,

and seem closer to antbirds of the genus

in this respect.

RESULTS

1. Cercomacra cinerascens

(Gray Antbird) individuaIs briefly visited

Bra-zilian raids of the army ant

at Maloquinha

at Belém (2),

and at Reserva Ducke

near Manaus. Oniki (1972) onde found a pair at a

raid at Belém. NormaIly

peers, hops, and "sings" series of a few

double notes in dense canopy vine tangles at forest edges or atop

second growth, but ignores ants. At Andoas, Peru, two birds alternated

and

notes, in a fast song duet, so that at least sorne songs may be

duets. One

that emerged from a tangle near ants at Manaus was

promptly displaced by a larger antshrike

A rattling

"snarl",

and a thrushlike

are the alarm

notes most often heard.

2. Cercomacra nigricans

Oet Antbird) pairs (2) disputed over a forest-edge

raid of

on the Bohio Peninsula, Panama, 5 Feb 1962. During

the dispute, the pairs pivoted back and forth and spread their backs, tai!s and

wings, showing large white shoulders and back patches as well as (normally

exposed) white wing bars and tai! tips. "Songs", series of a few

double notes, introduced and ended the dispute. The pairs hopped and peered

through liana tangles atop saplings 6-12 m up as in normal foraging behavior.

They gave faint "grunting"

and "cawing"

notes during the dispute.

The tai! often waggled from side to side or was jerked upward slightly. One

female gave a nasal

"snarl" at me, and one male puffed out his throat

to show white feather bases, but mostly

hop and peer along in dense

vine tangles high at forest edges or in second growth and pay little attention

to an observer. Over ants, they examine overhead vines and leaves, salIying

to the air nearby (4 records) or pecking tiny prey off leaves

and return

to the ants sporadicaIly over a period of several hours_

3. Cercomacra tyrannina

(Dusky Antbird) were at 62 ant raids, alI of

except for pairs at 2 raids of

in the

Mad-den Forest Reserve, central Panama, and at 2

raids at Bacabal,

428 Revta bras. Zool.

ranhão, Brazil. Other Panama raids were 5 in the Forest Reserve (4 with pairs, 1 with 2 pairs), 1 on Barro Colorado lsland (3 birds), 5 on the Bohio Peninsula (4 pairs, 1 lone bird) , and 1 with 1 bird on the Escobal Road. At Mitú, Colombia, 2 raids, were attended by 1 bird and 1 raid by a pairo ln

Brazil, tyrannina attended 37 raids at Reserva Ducke, near Manaus (1 with 4

birds, 1 with 3, 13 with 2, and 21 wilh 1) and 6 aI Belém (4 with 2 birds, 2 with 1).

Most Iyrannina attended raids briefly, but some followed up to 185 min

(Bacabal). Normally the species follows anIs only while lhe anIs move through dense second growth or dense scrub along roads, streams, or landslide areas.

There Iyrannina hop and peer low (at Manaus, 46-25-3 records from 0-3 m

up, by 1-m intervals) on slender perches (27-6-3 records from 0-3 cm diameter, by l-cm intervals) from horizontal to vertical (11-4-3-6-13 records from O to

100° from lhe horizontal, by 200 intervals). On vertical perches Iyrannina

tends lo angle upward, looking at overhead leaves rather than at the ground in the fashion of a regular ant follower; and Iyrannina seldom wails more than a few seconds per perch. The mobile neck may snake downward to look under leaves or vines. The perches and leaves or vines that Iyrannina examines are usually elose together, requixing little flight. Prey captures over ants in various regions involved mostly short-distance gleaning (leaves 23, vines or stems 8, trunk 1, air 1), rarely short sallies (ground 3, debris 1, leaf 1, stern 1). Prey items ineluded 2 ants and 2 smaIl grasshoppers.

OccasionaIly a regular ant-follower supplanted a Iyrannina: Tricholhraupis

penicillala (1) at Belém, Gymnopilhys ru/igula (3) and Percnostola ru/i/rons

(1) at Manaus. One supplanted Iyrannina female in Panama crouched, then

stood up and resumed foraging and tail-twitching. Disputes between territorial pairs of tyrannina commonly involve "chipping" dit-ik or dit-it-ik notes plus "snarling" snare notes. ln Panama, lhe snarling note was a rattling chra-a-a-a-a-ah. Birds spread their back feathers to show the white bases as back patches as they hop about, flicking their spread tails upward slightly or twi'tching them in circular motions. Two combatants in the Forest Reserve dropped their remiges slightly. "Songs" commonly end disputes, males at

Ma-naus singing downscale and accelerating her, her, her-hew-oo-oo-oo-oo-oo series

and females upscale hooh, hew, hee, hie-hih-ee-e-e series. At Belém, and once

at the Campina Reserve near Manaus, the male song was a very different per

peler peler peter peter, while the female song was like that at Reserva Ducke. Pairs of tyrannina keep in contact in their dense habitat by countersinging, the male giving one song and the female a different ·one. At Manaus, one male chipped each time the female answered his song. At elose range, male and female exchange faint chut or chut-chit "chirps". A grown young in female

pi um age at Reserva Ducke, 12 Aug 1974, gave chut-chut or chut-chut-chut

faintly as she followed the male, which fed her once; the female of the pa;r wandered nearby but ignored the young female. Two females with a male on Barro Colorado, 31 Jan 1977, suggest that young may stay with their parents until the next breeding season .

At a human, tyrannina often "chirr" nasally, chirrn, or snarl faintly and flick their tails upward slightly. At Bacabal, a pair gave single dit "chi ps" at

a forest-falcon (Micrastur ru/icollis). Dusky Antbirds quickly hide behind

ve-getation, and are hard to keep in sight, but do not flee faro One femaie, netted at Reserva Ducke, weighed 16.4 g and had a cloacal lemperalure of 41.7°C; she was in wing molt 30 Mar 1974 (primary 6 on each wing half grown).

4. Cercomacra serva (Black Antbird) followed an Eciton burchelli raid in tall roadside second growth aI Zatzayazu 500 m, Ecuador, 21 Oct 1965. The pair wandered and peered through dense saplings and vines at 1.8 to

2.5 m up, much like tyrannina. This species seems related to tyrannina, for

several nasal jew or jaw notes at Umbria (Colombia), at Zatzayacu, l:!1d at Andoas (Peru) .

5. Cercomacra nigrescens (Blackish Antbird) pairs foIlowed Eciton bur-chelli raids in dense fringing growth along a river at Yaapi, Ecuador, 14 Nov 1965 and along a road at Itaituba , Brazi!, 3 Mar 1966. They flitted the wing tips frequently as they hopped and peered in dense bamboo, cane, vines, and bushes 2-4 m up . The Yaapi male flitted his wings as he fed the female , and they gave rattling "chirrs", cha-a-a-a-a-a-a-a, followed by cha-cha-cha-cha-cha-cha-cha-cha-cha faint "songs" from the male. The alarm call at Itaituba, howe-ver, was a nasal chow or chert nyaah and the " song" from there west to Cashibococha (Peru) boong, heer-eer-eer-eer or boong, hear hear rather like one

song of tyrannina. ln most areas, nigrescens is a bird of dense zones along

streams or along roads through forests, like the Greater Ani (Crotophaga

major) .

6. Schistocichla atrothorax (Black-throated Antbird), often placed in the

genus Myrmeciza but actuaIly intermediate between Cercomacra antbirds and

the folIowing ｳｰ･｣ｩ･ｾ Ｌ＠ briefly foIlowed 3 Eciton burchelli swarms in dense

grass and bushes at forest edges at Reserva Ducke. It hops and peers in

very dense vegetation on or near the ground, and one at an ant swarm

pecked a smalI insect from debris, 0.1 m up. Although like a Cercomacra in

shape and size, it flicks its tai! upward like the following species, which it resembles in color. The alarm notes of atrothorax are a sharp chip and a loud veer. Disputing pairs along the edge of a swamp at Andoas , Peru, spread their back feathers to show white back patches, and gave double chips as well as veer notes and piercing he-he-he-he-he-Héep-Héep "Songs" much like those of the species at Manaus.

7. Schistocichla leucostigma (Dot-winged Antbird) irregularly followed

20 raids of Eciton burchelli along forest creeks at Reserva Ducke (8 with 1

bird, 10 with 2, and 1 each with 3 and 4) , 1 raid at Yaapi, Ecuador (2 birds), and 1 raid of Labidus praedator at Cacau Pereira, Brazi! (2 birds ; across the

Rio Negro from Manaus) . It normalIy hops on the ground , in broad-leaved

grasses, and in treefalIs or under logs and dark vegetation low along forest creeks, and follows ants in such sites or up nearby slopes as far as 25-30 m from creeks. At Andoas, it also foraged low in dark and debris-laden ald f100dplain second growth at some distance from the Pastaza River. Prey attempts over ants included a peck at a leaf and at the air, tossing leaves an the ground and short sallies to the base of a trunk and to the air. The alarm notes include a loud "chipping" chik-ik, a "rattling" di-i-i-i-ih and a sharp descending éeeeu, accompanied by upward flicks of the tail. Faint "chirps" , peup, go between mates or young and adult (1 Jan 1974, grown young in female plumage folIowing a female at Reserva Ducke); the song is a rapid he-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e trill. While leucostigma at Manaus once supplan-ted Pithys albifrons and twice supplanted Percnostola rufifrons, a Gymnopi-thys rufigula displaced a leucostigma there.

430

9. Drymophila genei (Rufous-tailed Antbird) briefly visited a Labidus praedator raid in upland bamboo forest at 1700 m in Itatiaia National Park, Rio de Janeiro, Brazil, 14 Sep 1975. The pair soon drifted away in the low, dense vegetation_ Alarm notes included a peest and a snaihhhht snar! or rattle; one of a pair "sang" a descending heest heest heest heest, jaihh and the other

a descending heest jaihh jaihh jaihh jaihh jaihh. 26 Nov 1977, young called

after adults pecking insects from leaves, away from ants. Normally genei fora-ges low in dense bushes, away from ants, above 1500 m el.

10. Hypocnemis hypoxantha (Yellow-browed Antbird) briefly followed Eciton burchel/i near a nest at Mitú, Colombia, and (one bird) near Mana-capuru, Brazil. The pair at Mitú, 3 May 1966, often dropped their tails 30°, a slow "pounding" motion, as they hopped and peered 2-10 m up in leaves and dense epiphytes along the edge of a swampy forest swale. They gave faint "songs" when birds or I approached their cup nest, and also before carrying food to young in the nest: a slow descending heep heep hip hip hoop hoop hoop. The "chirr" of alarm is a nasal chowrrr. This genus probably

should be joined to Drymophila.

11. Hypocnemis cantator (Warbling Antbird) followed 62 ant raids, 5 at

Nappi Creek, Guyana (Oniki & Willis, 1972), 4 at Mitú, Colombia, I each

at Limoncocha and Putuimi, Ecuador, and 51 in Brazil (I Coatá, 5

Maloqui-nha, 2 Serra do Navio, and 35 with I bird and 8 with 2 birds at Reserva Ducke, near Manaus). Two raids at Mitú and 2 at Maloquinha also had

single birds, but pairs were at other raids, including one raid of Labidus

praedator at Mitú.

It ordinari!y wanders 2-) m up in dense patches of bushes or vines of the forest understory or edges, hopping and peering at overhead leaves, and fol-lows ants only irregularly. It is rarely supplanted (by one Percnostola rufifrons

at Reserva Ducke) or displaced (by one Gymnopithys rufigula at Nappi), for

it keeps away from other ant followers. Like Drymophila squamata, cantator

often sidesteps up vertical sprouts or vines. Over ants at Reserva Ducke, cantator favored low (28-23-12 records 0-3 m up, by I-m intervals), slender (27-7-1-1 records 0-4 cm diameter, by l-cm intervals), and horizontal to vertical (12-3-6-8-9 records 0-1000 above horizontal, by 20° intervals) perches, and pecked prey (off a leaf, liana, and the ground) or sallied short distances (to a leaf and a vine tangle). The only prey identified, a caterpillar, was probably not flushed by ants. Records over ants in other areas were similar: 4 pecks at leaves or (once) a stem, and 2 short sallies to leaves.

ln alarm and perhaps in foraging generally, cantator flits its wings out-ward frequently. The tai! twitches from si de to side, as in the genera Formi-civora and Herpsilochmus. The alarm "chirr", a buzzy chirrrt, resembles that of Pithys albifrons, as does the sick-ik "chipping" alarm. Pairs keep in touch with faint cheup "chirps" and cha-at "grunts", becoming a faint chweech weech weech weech as a presumed female flew to a male and was fed 4 Nov 1965 at Limoncocha. If not in sight of each other, the pair exchange "songs" at intervals: a rising her heap varying to her-hee-hee-heap, often ending in one or more nasal raaj notes: her, heap-raaj or the like.

Scratching its head over the wing, it raises its slight cresto

12. Formicivora grisea (White-fringed Antwren) briefly followed 5 Eci-ton burchelli raids in Brazi! (I bird each at Colinas, Maranhão, and on the Serra do Pareeis, Mato Grosso; 4 birds at 3 raids at Fazenda Timb6, Santo Amaro, Bahia). It wanders in dense bushes of low open second growth or sandy scrub (Pareeis), 0.3 to 4 m up, peering and pecking here and there. It twitches its tai! from si de to side, rather Iike a Cercomacra, but the twitch is a downward "pounding" motion rather than an upward "flick". The wings flit outward frequently, flashing the white flanks and probably startling in-sects into flight. The "song" is a regular series of 10 or so herk notes at 2 notes/sec, occasionally ending with a raah "snarl". A grown young bird,

1974 at Bacabal. Maranhão. One call is a faint tr-r-r-r-r-r "rattle" , and another is a herk or ti-serk rather like a single note of the song_

13. Formicivora iheringi (Narrow-billed Antwren) briefly followed 2 Eciton burchelli raids in liana-tangled dry woodland at Fazenda Alvorada, Boa

Nova, Bahia, Brazil, 7 Dec 1974.

It

foliage, 2-10 m up, flashing its wings to show white flanks and twitching its tail s;de to si de at times. A single male was at one raid, but at another raid the male of a pair supplanted a second male with a yer yer yer call while a female " rattled" e-e-e-e-e-e nearby. Both males showed white patches on their backs or shoulders. The "songs", series of 10 or so hear notes at 2 ·notes/sec,

resemble songs of Rhopornis ardesiaca in the sarne woodlots. A pair that

carne up when a Hylophilus poecilotis was scolding me pounded their tails

downward, as do birds of the genus Myrmeciza.

DISCUSSION

Antbirds of the genera Cercomacra and Schistocichla use very dense

green foliage and vine tangles for the most part, birds of the first genus hopping and pecking prey above the ground and birds of the second genus working near or on the ground. Dense foliage is patchy in distribution, which interferes with ant following. Where humans create large areas of dense

se-cond growth , Cercomacra tyrannina sometimes can follow ants for long

pe-riods. A second problem, however, is that Cercomacra and Schistocichla

mos-tly peck prey oH nearby foliage, so that they do not wait for ants to flush distant prt'y. For "nearsighted" birds of these two genera, the ants probably seem to flush little prey.

Cercomacra and Schistocichla seem to represent a monophyletic

assem-blage of gleaners in dense foliage They seem related to the genus

Myrmo-therula and probably to Microrhopias, which Wiley (1971) showed to be a bird of dense green foliage. These birds mostly twi tch their tails slightly rather than perform upward "flicking" or downward "pounding", but when they do move their tails in the vertical plane there is a tendency toward

f1icking, as in Thamnophilus and in such genera as Hylophylax and Pithys.

Another group of antbirds that g[ean in rather dense foliage in represented

by the genera Drymophila and Hypocnemis. It is possible that these strongly

spotted antbirds are another radiation from Myrmotherula, perhaps via the

genus Terenura, but Drymophila and Hypocnemis seem to "pound" their tails downward and thus to be related to another major lineage of antbirds: the Formicivora-Myrmeciza group of tail-pounding antbirds. Myrmeciza species wiU be considered in the next report of this series, while Formicivora is

con-sidered here. The Myrmeciza to Formicivora lineage may be related to

Myr-motherula, or may merely represent a lineage converging toward Myrmo-therula.

Antbirds

01'

lineage use dense green foliage, but not as dense foliage as preferred by

ant-birds of the Cercomacra-Schistocichla lineage. Formicivora hop through green

foliage in dry or semiopen zones much of the time, or even move to the relatively open ground leveI in dry woodlands where few other antbirds live. Formicivora species should be able to follow ants through a variety of patches of differing foliage dellsities, yet do not do soo Probably they are normaJ[y restricted by habitats too open and dry for ants, and seldom encounter any army ants other than probe units disoriented by too much sunlight. Antbirds

of the Drymophila-Hypocnemis group are like Cercomacra in being adapted

432 Revta bras. Zool.

ACKNOWlEDGMENTS

Studies were supported by grants from the National Science Foundat;on (especially GB-32921), the Chapman Memorial Fund of the American Museum of Natural History, and the National Geographic Society. I appreciate also the help of the Smithsonian Tropical Research Institute in Panama, the Instituto Nacional de Pesquisas da Amazônia, and the Agronomic Institute and MU'ieu Paraense Emilio Goeldi at Belém. Douglas Wechsler helped with observations at Manaus, and Yoshika Oniki helped in many ways.

REFERENCES

Oniki, Y., 1972. Studies of the guild of ant-following birds at Belém, Brazil.

Acta Amazonica

Oniki, Y. & E. O. Willis, 1972. Studies of ant-following birds north of the

eastern Amazon.

Ibidem

Wiley, R. H., 1971. Cooperative relationships in mixed flocks of antwrens