No abstract

A 1960—71 study of populations of color—banded ant—following antbirds of three species on a tropical—forested lowland reserve, Barro Colorado Island, showed that the small species (Spotted Antbird, Hylophylax naevioides) remained stable at about 20 pairs/km2. A medium—sized species, the Bicolored Antbird (Gymnopithys bicolor), decreased from about 3 pairs to 1.5 pairs/km2. A large species, the Ocellated Antbird (Phaenostictus mcleannani), declined from 1.5 pairs/km2 to near extinction–only one female remained in early 1971. Two of three other species that regularly follow army ants showed relatively stable populations, but a third large species (Barred Woodcreeper, Dendrocolaptes certhia) declined from two pairs to local extinction. Prior to 1960 a very large ground—cuckoo that follows ants had already become extinct there. Thus, the three largest of the seven original species that regularly followed ants were gone or nearly gone by 1970. The decrease in numbers of regular ant—following birds was not made up by increases in occasional followers. Detailed studies of antbirds showed no clear reasons for declines, except that annual mortalities of adults were high in Ocellated Antbirds (about 30%) compared to Spotted Antbirds (15%—17%) and nest losses perhaps higher in the former (96% compared to 91%). Nest mortalities were slightly lower (88%) and adult mortalities intermediate (about 25%) in Bicolored Antbirds. Female Ocellated Antbirds had higher mortalities than males. The antbirds renest repeatedly during long nesting seasons, up to 14 times per year for Ocellated Antbirds. However, to replace females of this species under Barro Colorado conditions 19 nestings per year would be needed. Concurrent listing of all birds of the island showed that 45 species of breeding birds, 22% of the avifauna present when the island was made a reserve, had disappeared by 1970. No new species replaced them. Of the lost species 13 are forest birds, in danger if forests are cut elsewhere. The other species, second—growth and forest—edge birds, have been crowded out by growth of the forest. Loss of species from this tropical reserve, especially the part apparently caused by the small size and isolation of the reserve, poses problems for conservation and ecological studies of tropical biotas. It is suggested that large future reserves have corridor zones to each other, that is, that intensive human use not preempt too much area nor interrupt immigration of animals or plants from one refuge to another.

This series, published by the American Ornithologists' Union, has been established for major papers too long for inclusion in the Union's journal, The Auk. Publication has been made possible through the generosity of Mrs. Carll Tucker and the Marcia Brady Tucker Foundation, Inc.

Willis, Edwin O. The Behavior of Ocellated Antbirds. Smithsonian Contributions to Zoology, number 144, 57 pages, 25 figures, 1973.-A ten-year study of color-banded Ocellated Antbirds (Phaenostictus mcleannani) on Barro Colorado Island, Panama, showed that they persistently follow army ants for arthropods flushed by the ants. Dominant over the smaller antbirds that follow ants, they take the best zone low over the center of an ant swarm and drop to the ground for prey. They rest and preen for long periods of maintenance behavior each day, probably because as dominant birds they get food easily. Alarm behavior is similar to that of other antbirds. Agonistic behavior contrasts with other antbirds in having a silent challenging display and an unusually wide spectrum of submissive calls and postures. Courtship is mainly courtship feeding and singing; monogamous mates stay together for years. The nest is probably sunk in the ground between tree buttresses. Males incubate in the morning and late afternoon, females in the early afternoon and at night. Males and females feed nestlings and fledglings. Pairs renest repeatedly during the rainy season, April to December, but nest predation is high. Young are feeding themselves a month after appearing at swarms with their parents, but then irregularly stay with their parents up to several months (females) or years (males). Loose patrilineal clans form, in which gene transfer between clans is mainly by movement of young females. Daughters-in-law are tolerated. Clan members sometimes forage together, but use much submissive display. They close ranks or "bunch" in disputes with other pairs or clans. The social system is somewhat like that of chimpanzee groups and perhaps like that of early mantwo other dominant animals dependent on local and varying sources of food. The clan system permits complete overlap of home ranges of pairs. The parental pair in an area tends to dominate trespassing pairs and their own offspring. This social system permits great local concentration over good ant swarms. It is facilitated by tolerance for related birds, silent (and thus less disturbing) challenging, and by a wide variety of submissive displays. The Ocellated Antbirds on Barro Colorado concentrated at ant swarms on escarpment zones near the center of the island. Even with these concentrations, however, the species declined to near extirpation between 1960 and 1971. OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded in the Institution's annual report, Smithsonian Year. SI PRESS NUMBER 4774. SERIES COVER DESIGN: The coral Montastrea cavernosa (Linnaeus). Library of Congress Cataloging in Publication Data Willis, Edwin O. The behavior of ocellated antbirds. (Smithsonian contributions to zoology, no. 144) 1. Ocellated antbird-Behavior. I. Title. II. Series: Smithsonian Institution. Smithsonian contributions to zoology, no. 144. QL1.S54 no. 144 [QL696.P2] 591'.08s [598.1'11] 72-13261 For sale by the Superintendent of Documents,

Some 231 birds were recorded on a sandy plateau in central Sao Paulo, in an area forming a natural "habitat spectrum", from dry or wet grasslands to bushy ones (campo-cerrado) plus gallery scrub, marshes, and low woods. Subtracting 12 species that mostly flew over, and 56 species that seemed to be vagrants or accidental visitors, 163 species were regular (including 14 that center in nearby anthropogenically-modified zones). The 69 in gallery areas are mostly regionally common woodland species, but one southeastern species has disappeared over the years and three northwestern dry-forest species have entered. The 81 grassland species include several rare birds, and hence are important despite exhibiting lower biodiversity than in regional forest areas. Seven rare species disappeared over the years, some due to lack of fires, others because of either recent "greenhouse" dry years or protected vegetation growing to taller campo-cerrado. Several other species are becoming rare. Low vegetation forms a spectrum of temporally unstable habitats that change rapidly; one needs actively managed large areas and corridors even though many open-area birds can fly long distances to varying habitat patches.