AUSTRALIAN 192 WATCHER

AUSTRALIAN BIRD WATCHER 1997, 17, 192-197

Notes on Vocal Behaviour and Breeding of the Plumed ocellatus plumiferus by G.R. BERULDSEN, 47 Broadmoor Street, Kenmore Hills, Queensland 4069

Summary Nocturnal field observations were conducted on the Plumed Frogmouth Podargus ace/latus plumiferus over September-December 1996 in subtropical rainforest of the D' Aguilar Range near Brisbane, Queensland, at times with the aid of playback of tape-recorded calls. The Frogmouth sometimes responded silently to playback, by approaching the source of broadcast calls. Plumed appeared to start calling later in the evening than did some other nocturnal . The P. strigoides sometimes occurred in rainforest and appeared to react aggressively towards the Plumed Frogmouth. An occupied nest of the Plumed Frogmouth was located on 28 October, in the fork of a rainforest sapling, and regularly observed until the single nestling fledged at the end of November or the beginning of December. The parent brooding by day was apparently the male, both sexes visited the nest at night during the nestling phase, and the nestling period lasted at least 31 days. Introduction Little has been recorded on the breeding of the Podargus ocellatus, and then mostly on the northern subspecies P.o. marmoratus of Cape York Peninsula (Schodde & Mason 1980, Hollands 1991). Data are limited to a few records of nest site and construction, laying season, clutch size, brood size and description of downy young. Furthermore, from data on sexual dimorphism, parental roles and rufous morphs in females of the Marbled and other frogmouths (Schodde & Mason 1980), it is apparent that Hollands (1991) incorrectly assigned gender to the adult frogmouths he was observing at nests (all species) and hence his information on sex roles is questionable (see Debus 1992). The supposed breeding record of Welsh (1933) for the southern subspecies, Plumed Frogmouth P.o. plumiferus, has been referred to the Tawny Frogmouth P. strigoides (Schodde & Mason 1980). Therefore, the only information on breeding of the Plumed Frogmouth concerns a nestling found in a creek late in the year (Fleay 1981), indicating laying in spring and a creekside nest­ site within subtropical rainforest. Britton (1990) listed a report by I. Tarrant of a pair of Plumed Frogmouths 'nesting' in July, but no further details or observations of that event have been published. The Marbled Frogmouth has three principal and well-known calls: the koo-loo, the gobble or 'laugh/bill-clap', and the rapid drumming or 'Cane Toad' call (e.g. Schodde & Mason 1980, Hollands 1991, Corben & Roberts 1993). Response of the Marbled Frogmouth to playback of tape-recorded calls has been described by Hollands (1991), who found that in the breeding season the birds always replied. Similarly, Corben & Roberts (1993) found that playback elicits a response. Their list of negative locations, where no response was detected, was taken as implying the bird's absence from those survey sites. Meggs (1993) described calling behaviour and response to playback, noted that the birds call at any time of the night, and found that some false negatives proved positive on a second survey at those sites. The Tawny Frogmouth sometimes occurs in rainforest (Corben & Roberts 1993), particularly along roads and tracks (Debus 1992), although the latter may partly reflect observer bias. As well as misidentifications and consequent false records of Marbled Frogmouths, occurrences of the Tawny Frogmouth in rainforest could result in interactions between the two species. VOL. 17 (4) DECEMBER 1997 Vocal Behaviour and Breeding of Plumed Frogmouth 193

This paper describes a breeding record of the Plumed Frogmouth, its calling behaviour and response to playback, and interactions with the Tawny Frogmouth.

Study area and methods Observations were conducted in the subtropical rainforest of the D 'Aguilar Range near Brisbane, Queensland, from September to December 1996 with the aid of tape-recordings made of both subspecies of Marbled Frogmouth. The present study was preceded by familiarity with the northern subspecies on Cape York Peninsula, including nocturnal observations, tape-recording and playback of its calls (e.g. Beruldsen 1993). When an active nest of the Plumed Frogmouth was discovered in late October 1996, regular day and night observations were conducted, sometimes with Erina Beruldsen (hereafter EB), until early December when the fledgling could no longer be located. Night observations generally terminated around 2100-2130 h. Plumed Frogmouth territories were located by listening and using playback from ridges and gullies, and plotting the calling centres of simultaneously calling neighbouring pairs by triangulating from different points, taking account of sexual differences in the kooloo and gobble calls. For instance, close and distant calling birds at the junction of three gullies, in different directions, were investigated by forays up and down the gullies, noting from various points whether calling birds were upstream or down. However, no attempt was made to plot territory boundaries. Field identification The Marbled Frogmouth has a reputation for being difficult, if not impossible, to distinguish from the Tawny Frogmouth by morphological criteria in the field. This reputation rests largely on inexperienced observers relying on plumage characters, and consequently mistaking immature or rufous­ morph Tawny for Marbled. However, the difficulty is overstated as the two species differ substantially in build: Tawny is bulky, with massive head and bill and rather short, ragged tail; Marbled is slender, with finer head and bill and long, sometimes forked tail (e.g. Fleay 1981 , Hollands 1991). Consequently, their silhouettes differ (visibly so even at night). Furthermore, the underparts of the Tawny Frogmouth are streaked whereas those of the Marbled Frogmouth are marbled, distinguishably so in good views by day or when illuminated at night. The Marbled Frogmouth occasionally utters a soft oom-oom... call somewhat like that of the Tawny Frogmouth (Beruldsen 1993). With experience, they are distinguishable on quality: the normal droning oom-oom... call of the Tawny Frogmouth differs from the equivalent Marbled Frogmouth call by being louder and more resonant, whereas that of the Marbled is inaudible beyond 10-20 m. These morphological and vocal differences were used to identify the respective species in the following account of interactions between Plumed and Tawny Frogmouths. Ultimately, the most important criteria for distinguishing the two species were the kooloo and gobble calls of the Plumed Frogmouth.

Vocal behaviour

Response to conspecific calls My experience of the response by this species to playback is that although a response can be obtained throughout the year, a vocal response in a known area cannot always be expected. There were occasions when I played the tape in a known territory without eliciting any vocal response, only then to find, with the aid of a spotlight, a Marbled Frogmouth sitting quietly on a branch overhead, apparently having been attracted by the playing of the taped call. Even when a call was played with the bird under observation by spotlight, the only response was a movement of the head toward the source of the call. On other occasions, including on Cape York Peninsula but especially with the Plumed subspecies in south-eastern Queensland, I have found that calling did not commence until 1.5- 2 hours after sunset, often an hour or more after Southern Boobooks Ninox novaeseelandiae or Sooty Owls Tyto tenebricosa started calling. Likewise, I found a corresponding reluctance by the Plumed Frogmouth to answer playback until that hour. I frequently found that I could not elicit any vocal response to playback, of any of the three principal calls of the bird, for instance in October, until 1930-2000 h. AUSTRALIAN 194 BERULDSEN BIRD WATCHER

Interactions with Tawny Frogmouth Through September and October 1996 I spent about 80 night hours in the forest of the D' Aguilar Range, listening to the calls of the Plumed Frogmouth and locating territories. Tawny Frogmouths occasionally appeared in some of the territories, despite the habitat being closed-canopy rainforest up to 0.5 km from the nearest roadways or eucalypt forest. Plumed Frogmouths sometimes responded, as described below, to the presence of a Tawny Frogmouth within a territory. On the afternoon of 28 September, I located a Tawny Frogmouth (with heavily streaked underparts, no marbling) perched in the forest within a known territory of a pair of Plumed Frogmouths. After dark that evening the droning oom-oom ... calls of a Tawny Frogmouth could be heard in the gully close to where the perched bird had been seen that afternoon. No Plumed Frogmouths were heard to call that evening, at least until I left around 2100 h. The Tawny Frogmouth was then still calling. Despite playing a tape that night of three of the Plumed Frogmouth's calls (kooloo, gobble and 'toad' call), no vocal response from any Plumed Frogmouth was detected, notwithstanding frequent calling by the birds in the same area on the previous night. The weather was similar on both evenings, clear and still with the moon almost full. Between 30 September and 24 October Plumed Frogmouths called each night that I visited (about 10 nights, every second or third night), but no further Tawny Frogmouth calls were heard. On the night of 26 October Plumed Frogmouths commenced calling (kooloo and gobble), but only occasionally, shortly after 1930 h. By 2000 h the birds were calling frequently from five different locations, all clearly audible from where I was listening. At about 2010 hI played a taped Plumed Frogmouth call (gobble) and immediately a frogmouth approached and landed, the silhouette being clearly visible against the sky. It then called from directly overhead, with the typical gobble of the Plumed Frogmouth. Some minutes later a Tawny Frogmouth gave a droning oom-oom... call nearby, whereupon all the Plumed Frogmouths became silent (possibly as a response to the Tawny Frogmouth). With the aid of a spotlight a Tawny Frogmouth (with bulky silhouette and boldy streaked underparts) was located high overhead, close to where we had seen the Plumed Frogmouth (which by then had moved from its perch). While EB held the spotlight on the Tawny Frogmouth I again played the Plumed Frogmouth call; the Tawny Frogmouth immediately looked down in our direction, apparently seeking the source of the Plumed Frogmouth call. As EB lowered the spotlight off the Tawny Frogmouth we noticed a Plumed Frogmouth (with gracile silhouette and marbled underparts) perched on a low sloping branch, about 1.5 m above the ground and little more than 3m from where we were standing. The bird was staring intently, steeply upwards at the point where the Tawny Frogmouth was perched, in what might have been a cryptic pose; the Plumed Frogmouth was clearly watching the larger bird. We observed the Plumed Frogmouth for almost 10 minutes, moving around for different views of the bird. It appeared to be completely oblivious to our presence and ignored the spotlight, maintaining a fixed stare in the direction of the Tawny Frogmouth. After 10 minutes our activity flushed the Plumed Frogmouth and it flew off. It was not until almost 45 minutes after the Tawny Frogmouth had stopped calling that Plumed Frogmouths starting calling again. In that 45 minutes we had, on several occasions, played a tape of Plumed Frogmouth kooloo and gobble without eliciting a vocal response. In the above observation, a Tawny Frogmouth approached and apparently displaced a territorially calling Plumed Frogmouth, then commenced its own territorial calling; it appeared to react aggressively to the source of Plumed Frogmouth calls. The Plumed Frogmouth avoided the Tawny by seeking a more sheltered perch, in a possibly cryptic VOL. 17 (4) DECEMBER 1997 Vocal Behaviour and Breeding of Plumed Frogmouth 195

Nest and hatchling of Plumed Frogmouth Podargus ocellatus plumiferus, D'Aguilar Range, Brisbane, Queensland, October 1996. Plate 20 Photo: G.R. Beruldsen pose, while warily watching the larger bird. The ensuing silence of all the local Plumed Frogmouths, in the presence of the calling Tawny Frogmouth, may also have been avoidance behaviour.

Nesting On the afternoon of 28 October, while in the forest attempting to find daytime roosts of the Plumed Frogmouth, I observed one sitting in a three-pronged vertical fork in a sapling about 6 m above the ground. The bird appeared to be sitting on a nest, although the only evidence that could be detected from the ground was a short, single strand of a small-leaved climbing fern hanging down from the fork, under the breast of the bird. There was no evidence of that fern type elsewhere in that tree. Later inspection that day revealed a nest of moss and small pieces of fern, built on the trunk of the sapling where it divided into three branches. The nest was 12 X 14 em across and about 4 em deep, almost flat across the top. It appeared to have been used previously, perhaps over some years, for much of the depth of the nest was old rotten material with simply a layer of new moss and small pieces of fern laid over the top. On discovery, it held a single newly hatched chick: a tiny ball of white down (Plate 20). The sapling was a Scentless Rosewood Synoum glandulosum (G. Smith pers. comm.), about 12-15 m tall, in subtropical rainforest at the headwaters of a creek and on a hillside 50 m above the floor of the gully. There was no running water in the AUSTRALIAN 196 BERULDSEN BIRD WATCHER gully, which flows with a small volume of water only after heavy rain; the nearest gully with permanently running water was about 1 km away. Each night through November, the bird that had been at the nest brooding the chick throughout the day remained on the nest until it was almost dark, departing at about 1840 h each night. From its colour and markings, the daytime brooding bird was thought to be the male on the basis of literature (e.g. Schodde & Mason 1980) and discussion with C. Corben; it was the larger, greyer and more strongly marked of the pair. Each niglit a bird, I could not determine whether male or female, arrived at the nest and fed the chick around 1900 and again around 1915 h, but then neither parent returned to the nest during the next 1.5-2 hours. On one occasion one of the parents flew up to the nest while the other was still standing by the nest feeding the chick. I heard a sharp exchange of aggressive calls and the bird that had just flown in immediately departed. It appeared that the bird already at the nest drove off its just-arrived partner. At no other time did I see two birds together at the nest. The feeding pattern, that is 1900 and 1915 h then nothing until I left around 2100 h, was the same every night whether or not it was clear and moonlit, windy or raining. On several occasions it was raining while I watched. The adult which came to the nest to feed the chick appeared to try to shelter the chick from the rain, with its breast, for perhaps five minutes or more before departing. On the night of 22 November, soon after its second feed at about 1930 h and in the absence of the parents, the chick was seen to stand up on the nest and exercise its wings for 10 minutes, the only time it was seen to do so. It was then at least 25 days old. Between the night of 28 November and the early morning of 2 December, the nestling left the nest. I could not find the fledgling or parents on that day. The nestling period was therefore at least 31 days. On 4 December the two adults and the fledgling were located roosting together in a dense vine-thicket 20 m from the nest. The fledgling was pressed tightly against the male, with the female about 2 m away. Thereafter I was unable to locate the birds in the daytime and unable to elicit any response to the playing of a tape at night, notwithstanding that I was playing a tape of the calls of that particular pair of birds. Observations were discontinued on 7 December, after several futile attempts to locate the birds either in daylight or by response to nocturnal playback. Throughout my observations of the nestling period, both parents consistently refused to respond vocally to playback; I had to move 100m away from the nest before I could elicit any vocal response from the parents to playback.

Discussion It is apparent that lack of response to playback cannot be taken as evidence of absence of the Plumed Frogmouth from a particular locality, as also found by Meggs (1993). Repeat surveys may be needed, and spotlighting may also be required to detect responding individuals that approach silently. Indeed, standardised surveys of nocturnal forest birds usually incorporate a listening, playback and stationary spotlighting component, with at least two surveys per site, and even then some birds are missed (e.g. Debus 1995). Marbled Frogmouths may prefer certain times of the night for calling, as do other nocturnal birds (e.g. Debus 1995 and in press) and, like the Tawny Frogmouth, they may be deterred from calling by the calls of owls (Debus in press). It is also apparent that Tawny Frogmouths respond aggressively towards Plumed Frogmouths, and that the smaller Plumed Frogmouths therefore behave warily towards Tawny Frogmouths. Such an interpretation is suggested by the interaction described in this paper, and supported by instances of Tawny Frogmouth calling apparently VOL. 17 (4) DECEMBER 1997 Vocal Behaviour and Breeding of Plumed Frogmouth 197 deterring Plumed Frogmouth calling. Construction of roads and tracks through rainforest, e.g. during forestry activities, may allow Tawny Frogmouths to penetrate Plumed Frogmouth habitat and may consequently bring the two species into interspecific competition. The breeding record herein agrees with the laying season, brood size and chick morphology of the northern Marbled Frogmouth (see Schodde & Mason 1980, Hollands 1991, Strahan 1994), and provides additional evidence that the Plumed subspecies lays in spring (see Fleay 1981). The nest-site in this study was not near a permanent creek (1 k:m away, cf. Meggs 1993), although it was in the gully of an intermittent creek. The nest-site in this study suggests both that suitable forks in large saplings should be readily available in regenerating or multi-aged forest, and that the Plumed Frogmouth might re-use traditional nesting sites. With sufficient records of the identity of nest trees and nesting material, a pattern of nest-site characteristics for the Plumed Frogmouth may emerge. Both sexes of the Plumed Frogmouth visited the nestling at night. That the male broods by day is consistent with morphological and behavioural information on the Marbled and other frogmouths (see Schodde & Mason 1980). However, this study and the literature conflict with Hollands (1991) who incorrectly assumed that the larger, greyer and more strongly marked sex in frogmouths, and which broods by day, is the female, and that the smaller, plainer, more rufous (or rufous-morph) sex which roosts near the nest by day is the male. In fact, it is the other way round: males incubate/brood by day, and the smaller, redder individuals of a given species are females (Schodde & Mason 1980). Furthermore, G.C. Smith has found by radio­ telemetry that the male Plumed Frogmouth incubates or broods by day while the female roosts elsewhere (Anon. 1993).

Acknowledgements I thank Robert Mahoney and my wife Erina for their assistance in the forest at night, Stephen Debus and two referees for valuable assistance with the manuscript, and Dr Geoff Smith (Dept Natural Resources, Indooroopilly) for comments on a draft and identification of the nest sapling. References Anon. (1993), 'October meeting [report]', Qld Ornithol. Soc. News[. 24(10), l. Beruldsen, G.R. (1993), 'The undescribed oom-oom-oom call of the Marbled Frogmouth', Sunbird 23, 93-94. Britton, P.L. (1980), 'The Queensland Ornithological Society bird report 1989', Sunbird 20, 64-82. Corben, C. & Roberts, G. (1993), 'Some recent records of the Plumed Frogmouth Podargus ocellatus plumiferus', Sunbird 23, 61-72. Debus, S. (1992), Review- Birds of the Night: Owls, Frogmouths and Nightjars of Australia, Aust. Bird Watcher 14, 320-321. -- (1995), 'Surveys of large forest owls in northern New South Wales: methodology, calling behaviour and owl responses', Corella 19, 38-50. --(in press), 'Vocal behaviour of the Southern Boobook Ninox novaeseelandiae and other nocturnal birds', in Czechura, G. V. & Debus S.J .S. (Eds), Australian Raptor Studies II, RAOU Monograph series, Royal Australasian Ornithologists Union, Melbourne. · Fleay, D. (1981) , Looking at , Boolarong, Brisbane. Hollands, D. (1991), Birds of the Night, Reed, Sydney. Meggs, T. (1993), The Distribution, Abundance and Habitat Preference of the Marbled Frogmouth in the Northern Rivers Region, B.App.Sci. (hons) thesis, University of New England- Northern Rivers, Lismore (N.S.W.). . Schodde, R. & Mason, I.J. (1980), Noctuma? Birds of Australia, Lansdowne, Melbourne. Strahan, R. (Ed.) (1994), Cuclwos, Nightbirds & Kingfishers ofAustralia, Angus & Robertson, Sydney. Welsh, C.W. (1933), 'Eggs of Plumed Frogmouth', Emu 32, 193.

' \ Received 26 May 1997 •