Infanticide of nestling noisy miners, communally breeding honeyeaters

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and artificially-broadcast calls were not statistically significant ( M a n n - W h i t n e y U-test, z = 1.09, P = 0.22). Although the difference in the amount of attenuation of the whine for natural and artificially-broadcast calls is also relatively small, this difference is statistically significant (z=4.28, P<0.0001). These measures of the relative attenuation of the whine and chuck are consistent with previous results. Ryan (1985) conducted similar experiments in three habitats: open grassland, a gravel pit with no vegetation, and dense forest. P. pustulosus commonly breed in the first two areas, but not in the forest. In all habitats and over several distances, the chuck attenuated at a greater rate than did the whine. The proximate explanation for this phenomenon is that the chuck has its energy concentrated in higher frequencies, while the whine has its energy concentrated in lower frequencies. This is consistent with a number of bioacoustic studies demonstrating relatively lower rates of attenuation for low frequencies (e.g. Brenowitz 1982), as well as with acoustic theory that makes the same prediction (reviewed by Wiley & Richards 1982). These results suggest that, at least in this study, broadcasting the animal's signal gives qualitatively similar results to those obtained by measuring the attenuation of the signal actually produced by the animal. This technique is further supported by the fact that Ryan (1985) showed similar results in different habitats using a different broadcast system. This is the first demonstration of the validity of this technique for studies of environmental bioacoustics. However, this study also suggests caution in interpreting results of such studies. Although the results are qualitatively similar, they are not quantitatively the same in the comparison of the attenuation of the whine. The fact that there was no significant difference in the chuck, but there was in the whine, highlights the potential difficulties with such an experimental design. Of course, although the differences are significant statistically, they are so small that they might not be meaningful biologically. This study suggests that the technique of broadcasting an animal's signal through the environment for purposes of characterizing rates of attenuation might be fairly robust, although the cautions of Michelson (1978) should still be heeded. This study was supported by a grant from the National Geographic Society. I thank E. Brenowitz, R. Bowman, and C. Gerhardt for criticizing the manuscript. I am grateful to Kathy Troyer for field assistance, to the Smithsonian Tropical Research Institute for logistic support, and to the Miller Institute for Basic Research in Science, and the Museum of Vertebrate Zoology, University of

California, Berkeley for financial support during the field aspect of this research. MICHAEL J. RYAN

Department o f Zoology, University o f Texas, Austin, T X 78723, U.S.A.

References Brenowitz, E. A. 1982. Long-range communication of species identity by song in the red-winged blackbird. Behav. Ecol. Sociobiol., 10, 29 38. Gerhardt, H. C. 1975. Sound pressure levels and radiation patterns of the vocalizations of some North American frogs and toads. J. comp. Physiol., 102, 1-12. Gish, S. L. & Morton, E.S. 1981. Structural adaptations to local habitat acoustics in Carolina wren songs. Z. Tierpsychol., 56, 74-84. Michelson, A. 1978. Sound reception in different environments. In: Sensory Ecology." Reviews and Perspectives (Ed. by M. Ali), pp. 345 373. New York: Plenum Press. Morton, E. S. 1975. Ecological sourees of selection on avian sounds. Am. Nat., 109, 17-34. Rand, A. S. & Ryan, M. J. 1981. The adaptive significance of a complex vocal repertoire in a neotropical frog. Z. Tierpsychol., 57, 209 214. Ryan, M. J. 1980. Female mate choice in a neotropical frog. Science, N. Y., 209, 523 525. Ryan, M. J. 1983a. Frequency modulated calls and species recognition in a neotropical frog. J. comp. Physiol., 150, 217-221. Ryan, M. J. 1983b. Sexual selection and communication in a neotropical frog. Evolution, 39, 261 272. Ryan, M. J. 1985. The Tfmgara Frog: A Study in Sexual Selection and Communication. Chicago: University of Chicago Press. Ryan, M. J. & Brenowitz, E. A. 1985. The role of body size, phylogeny, and ambient noise in the evolution of bird song. Am. Nat., 126, 87-100. Ryan, M. J., Tuttle, M. D. & Rand, A. S. 1982. Sexual advertisement and bat predation in a neotropical frog. Am. Nat., 119, 136-139. Wiley, R. H. & Richards, D. G. 1982. Adaptations for acoustic communication in birds: sound transmission and signal detection. In: Acoustic Communication in Birds, Vol. 1, Production, Perception and Design (Ed. by D. E. Kroodsma & E. A. Miller), pp. 132-181. New York: Academic Press. (Received 24 October 1985; revised 11 November 1985," MS. number: AS-365)

Infanticide of Nestling Noisy Miners, Communally Breeding Honeyeaters Infanticide, once thought to be a rare phenomenon, occurs regularly throughout the animal kingdom, but its adaptiveness to individuals has been studied only recently (for a review, see Hausfater & Hrdy

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1984). Among birds, infanticide of nestling passerines is rare and is unreported for those that breed communally. However, several communal breeders destroy eggs of conspecifics (e.g. Mexican jay Aphelocoma ultramarina, Brown 1963, Trail et al. 1981; Florida scrub jay Apheloeoma coerulescens, Wolfenden & Fitzpatrick 1984; Arabian babbler Turdoides squamieens, Zahavi 1974; groove-billed ani Crotophaga sulcirostris, Vehrencamp 1978). From August 1978 through December 1981, I studied communal breeding of noisy miners Manorina melanocephala near Meandarra, 310 km west of Brisbane, Queensland, Australia. In 300 h of nest observation, I saw one adult male kill a nestling. Of the 38 other nests I monitored in 1980 and 1981, I suspect that infanticide occurred at three. Understanding the significance of infanticide requires knowledge of the noisy miner's life history, described by Dow (1978, 1979). These sedentary honeyeaters obtain virtually all their food within a colony, which they defend strongly from intruders. The activity spaces (sensu Dow 1979) of males overlap, and some groups or 'coteries' (Dow 1979) of males display aggression towards other males. Females' activity spaces do not overlap. Adult males outnumber females four to one at Meandarra. The sex ratio of fledglings, however, is unity. Both sexes mate promiscuously. Females attend only their own nests, but a male may visit the nests of several females in one day and many in one season. I observed infanticide on 22 October 1980. WYW (colour band combination), an adult male whose activity space was 300 m east of the nest, visited for the first time during the 4 h of observation which occurred over a 4-day period. The nest contained three young; the eldest and largest, GOG, was 12 days old. WYW carried no food when he arrived at 0818 hours. Leaning into the nest, he pecked GOG's head. GOG turned away, cringed and closed its eyes. WYW pecked it again and departed, 20 s after arriving. GOG immediately uttered a harsh, throaty and long squeal, which I had heard only twice before while handling young birds. Four adult males, all regular attendants, flew to the nest. GOG lurched upwards and fell on its side, legs and wings flailing. It did not move thereafter and was dead when I examined it at 0910 hours. An autopsy revealed a haemorrhage at the base of its brain. In 3 h of further observation, WYW did not visit. On 25 October, the smallest nestling was dead in the nest. I did not determine its sex nor the cause of its death. Its brood-mate had fledged recently. It is dangerous to characterize a phenomenon by extrapolating from an isolated event. It is worth-

while, however, to note that WYW was a member of a neighbouring coterie, was not a regular attendant at the nest, and was probably not closely related to any of the attendants or the nestlings at the nest. Furthermore, he was subordinate in nearly every intraspecific interaction I observed. Unlike other males, WYW did not attend nests in his own coterie-area in 1980; the attack I have described was the only time I saw him at a nest. Deaths at three other nests suggested infanticide. On 9 October 1981, one nest contained four nestlings: the first had hatched on 4 October. The following day, the second oldest of the brood was gone. On 17 October, I found the second youngest, a male, dead directly below the nest. He showed signs of a cerebral haemorrhage and the feathers on the back of his head were dishevelled. The two remaining nestlings fledged. At another nest on 5 October 1981, I found one egg and two tiny nestlings within the cup and another, newly hatched, on a branch about 20 cm from the cup. It was alive but had apparently been pecked about the eyes and neck and had a large bruise behind the cloaca. I returned this bird to the nest. Next day, I found it dead at the same spot, 20 cm from the nest. Its brood-mates fledged but the remaining egg failed to hatch. On 15 October 1981, another nest contained three eggs; the first was laid on 13 October. One newly hatched nestling, but no egg, was in the nest on 31 October. The nestling was found dead below the nest on 2 November but bore no external signs of injury. I could not determine its sex. Why might a miner commit infanticide? A subordinate male may reduce competition from conspecifics by attacking potential competitors when they are most vulnerable, i.e. in the nest, before the social bonds and coalitions that characterize the behaviour of miners are established. In the absence of adults, nestlings are helpless. Attacks at nests within the coterie-area of residence may be non-adaptive because of the higher degree of relatedness among adults that live there (personal observation) and the need for recruits (regardless of relatedness) for communal defence of the coterie-area. Nests outside the coterie-area are found easily because females advertise their locations while building them, many males attend them, and nestlings are unusually vocal (Dow 1978). Ricklefs (1969) used data on the survival of eggs and nestlings to characterize sources of mortality by (1) the magnitude of their effects at different stages in the nesting cycle and (2) whether they act on individuals or entire clutches or broods. When plotted on Ricklefs' axes, the mortality vector for miners is similar in direction and magnitude to a

Short Communications vector characteristic of starvation. Miners' withinbrood losses were 1.08% (1980) and 1:04% (1981) per day, figures relatively higher than those reported for most other species and similar to those of blackbirds and grackles (family Icteridae), which are often subject to starvation (Ricklefs 1969). However, within-brood effects of infanticide may mimic those of starvation in that both result in the loss of single nestlings rather than entire broods. If starvation was a principal cause of death at Meandarra, the difference between mortality rates in 1980 and 1981, when ecological conditions differed greatly (Whitmore et al. 1983), should have been greater than 0.04% per day. Even in 1981, a year when rainfall and food were plentiful, nestlings suffered a high mortality rate (56% overall). Furthermore, none of the six nestlings whose deaths I describe here showed obvious signs of starvation. Infanticide in miners occurs neither frequently nor predictably. Dow (1978) did not observe infanticide at Laidley, 72 km west of Brisbane. But he 'found dead nestling Miners on the ground surprisingly o f t e n . . . Many seemed intact.' (page 218). The deaths of six nestlings in four of the 39 nests that I observed suggested infanticide rather than mortality by other factors (predators, nest site competitors, brood and arthropod parasites). The relative influence of infanticide and starvation remains to be determined by watching miners' nests and, simultaneously, studying nestling growth. Meanwhile, the events I describe illustrate that inferences about sources of mortality in nests should be based not only on data about the survival of eggs and nestlings, but also on direct observations of activities at nests. I thank Douglas Dow for commenting on the manuscript. The Rotary Foundation, University of Queensland, and the Frank M. Chapman Fund of the American Museum of Natural History provided financial support. This is a contribution of the Meandarra Ornithological Field Study Unit of the University of Queensland. MARY J. WHITMORE*

Department of Zoology, University of Queensland, St. Lucia, Queensland 4067, Australia. * Present address: University of Michigan Biological Station, Pellston, Michigan 49769, U.S.A.

References Brown, J. L. 1963. Social organization and behavior of the Mexican jay. Condor, 65, 126-153.

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Dow, D. D. 1978. Breeding biology and development of the young of Manorina melanocephala, a communally breeding honeyeater. Emu, 78, 207-222. Dow, D. D. 1979. Agonistic and spacing behaviour of Manorina melanocephala, a communally breeding honeyeater. Ibis, 121, 423-436. Hausfater, G. & Hrdy, S. B. (Eds) 1984. Infanticide: Comparative and Evolutionary Perspectives.New York: Aldine. Ricklefs, R. E. 1969. An analysis of nesting mortality in birds. Smithson. Contrib. Zool., 9, 1-48. Trail, P. W., Strahl, S. D. & Brown, J. L. 1981.Infanticide in relation to individual and flock histories in a communally breeding bird, the Mexican jay (Aphelocoma ultramarina). Am. Nat., 118, 72-82. Vehrencamp, S. L. 1978. The adaptive significance of communal nesting in groove-billed anis (Crotophaga sulcirostris). Bchav. Ecol. Soeiobiol., 4, 1-33. Whitmore, M. J., Dow, D. D., Fisk, P. G. & Moffatt, J. D. 1983. An annotated list of the birds of Meandarra, Queensland. Emu, 83, 19-27. Woolfenden, G. E. & Fitzpatrick, J. W. 1984. The Florida Scrub Jay: Demography of a Cooperative-breedingBird. Princeton: Princeton University Press. Zahavi, A. 1974. Communal nesting by the Arabian babbler. Ibis, 116, 84-87. (Received 15 April 1985; revised 18 October 1985; MS. number: AS-335)

Maternal Recognition of Juvenile Offspring Coo Vocalizations in Japanese Macaques In a study of the vocalizations of wild Japanese macaques (Macaca fuscata), Green (1975) suggested that immatures direct Smooth-Late-High (SLH) coo calls toward their mothers. Coos are brief, tonal vocalizations that young macaques use while resting alone, soliciting contact, following their mothers, and during movement of other group members (Rowell & Hinde 1962; Green 1975; Lillehei & Snowdon 1978; Baker-Dittus, personal communication, Macaca sinica). The authors of all three papers cited above suggested that coos may be individually recognizable among conspecifics. Two previous studies, however, failed to demonstrate that macaque infant coos are individuallyrecognizable by mothers (Simons et al. 1968; Simons & Bielert 1973). This study was done to determine whether the SLH coo calls of Japanese macaque juveniles are individually recognizable by their mothers. I studied a group of 11 Japanese macaques that was permanently housed in an outdoor enclosure described by Candland et al. (1972). The group consisted of five adult females, two adult'males, three juveniles (22-23 months old), and one infant. The juveniles' vocalizations were recorded using a Dan Gibson Electronic Parabolic Microphone, an