152 AUSTRALIAN FIELD ORNITHOLOGY 2006, 23, 152–158 Observations of Predation, Nest-predation and Other Disturbance Events at Dryandra, South-western Australia II: Birds as Prey of Other Animals GRAHAM R. FULTON School of Natural Sciences, Centre for Ecosystem Management, Edith Cowan University, 100 Joondalup Drive, Joondalup, Western Australia 6027 (Email: [email protected]) Summary I describe nine predation, nest-predation and disturbance events: four by ants, four by the South-western Carpet Python Morelia spilota imbricata and one by the Bilby Macrotis lagotis. Predation by ants was more important on or near the ground, and Greenslade’s Meat Ant Iridomyrmex greensladei was responsible for three of the four events. The Carpet Python took Rainbow Bee-eater Merops ornatus nestlings from a burrow, and free-flying Australian Ringnecks Barnardius zonarius from the tree-canopy and from the ground. The Bilby dug out a Bee-eater’s burrow, which it either depredated or from which it caused the nestlings to fledge prematurely. All observations were made at Dryandra Woodland, a 27 000-ha remnant of woodland, with an almost full community of animals that have declined or disappeared from the surrounding wheatbelt, 160 km south-east of Perth, Western Australia. The context of each event is discussed in relation to the broader background of a 3-year community-wide study of Dryandra’s birds, which involved continuous monitoring throughout each breeding season. Introduction The identity of nest-predators is still poorly documented in Australia, although a few important nest-predators such as ravens Corvus spp., Pied Currawong Strepera graculina, Grey Shrike-thrush Colluricincla harmonica and Common Brushtail Possum Trichosurus vulpecula have been identified (Major et al. 1996, 1999; Fulton & Ford 2001; Berry 2002; Piper et al. 2002; Zanette 2002; Fulton in press). This paper presents accounts of predation, nest-predation and other disturbance events by a suite of less well-known and non-avian predators; although as individual species these are not considered important predators, they were collectively important at Dryandra Woodland, south-western Australia. The context surrounding each predation event is given and the diversity of predators identified at Dryandra Woodland is expanded (for details see Fulton 2006). Predators identified in this paper include the South-western Carpet Python Morelia spilota imbricata, which is listed as Schedule 4 specially protected fauna (Edwards 2005), and vulnerable (Cogger et al. 1993); Greenslade’s Meat Ant Iridomyrmex greensladei and Black- headed Sugar Ant Camponotus nigriceps; and the Bilby Macrotis lagotis, which is listed as Vulnerable C2a and Schedule 1, rare or likely to become extinct (IUCN 2004; Edwards 2005). Methods Scientific and common names for mammals were taken from Strahan (2002); for ants from McArthur & Adams (1996), Shattuck (1999) and Andersen (2002); pythons from Cogger (1996); and birds from Christidis & Boles (1994). The date format used here is dd/mm/yy. The study site (Dryandra Woodland south-east of Perth, Western Australia) is described elsewhere (Fulton 2006). I spent most daylight hours in the field each day throughout the breeding season (August to January inclusive) for three years, 2002–03, 2003–04 and 2004–05. Pythons in VOL. 23 (3) Observations of Predation II: SEPTEMBER 2006Birds as Prey of Other Animals 153 a house garden were observed from the cottage, which acted as a hide. Other observations of pythons were made opportunistically while observing birds (see Fulton 2006 for details of bird observations). Bilby diggings were compared with known Bilby diggings at Dryandra and with descriptions by Johnson (1989). Rainbow Bee-eater Merops ornatus nests were monitored by placing small sticks in the tunnel’s entrance; if these were moved the adult Bee-eater was presumed to have been to the nest. This approach was combined with listening for young in the nest when the nests had nestlings. Measurements of Bee-eater nest-burrows and observations of the chambers’ contents were made after the young had fledged or the breeding attempt failed. Ant specimens were collected at the site in a dry container and placed in 70% alcohol at the end of the day. Identifications were confirmed by Archie McArthur for the Black-headed Sugar Ant and by Brian Heterick for Greenslade’s Meat Ant. Results and discussion Ants attacking birds 1. 12/1/04 Black-headed Sugar Ants killed nestlings or inadvertently caused a Rainbow Bee-eater brood to fledge prematurely. This Bee-eater’s burrow was 118 cm long and 32 cm below the surface at the base of the nest-chamber. Burrows at Dryandra are dug into flat sandy soil in low-lying areas (unpublished data). Sugar ants Camponotus spp., not regarded as aggressive, are general scavengers that collect nectar and plant secretions, and tend Hemiptera for honeydew (Briese & Macauley 1981). In this case, they may have simply built their nest on top of the Bee-eater burrow. Upon excavation (5/2/04), the Bee- eater nest-chamber was found to have collapsed and was full of Black-headed Sugar Ants. A small amount of avian skeletal and feather remains was also detected. It is not known whether the adult Bee-eaters stopped coming to the nest because the nestlings were dead or because there were too many ants with which to contend. The Sugar Ants were first detected building their nest on 9/1/04, when detritus began to appear at the opening of the Bee-eaters’ nest-tunnel along with a few live worker ants. The Bee-eaters’ nest was active until 11/1/04, with adult birds still coming to their nest although detritus levels were increasing at the nest opening. Adult Bee-eaters stopped coming to the nest on 12/1/04. No fledglings were detected near this nest and the young were not due to fledge for another 12 days (based on averages of nests that fledged young). This is likely to be an unusual event: Black-headed Sugar Ants or any other sugar ants have not, to my knowledge, previously been reported taking vertebrates as food. Adult sugar ants are not able to ingest solid food particles of any size, although in this case the ants may have dismembered the small chicks to feed to their larvae (Brian Heterick and Archie McArthur pers. comm.). Adult sugar ants feed on carbohydrate, and their larvae are fed on protein (Briese & Macauley 1981; A. McArthur pers. comm.). The larvae exist for only a short period in the annual cycle, which varies with each species (A. McArthur pers. comm.). Similarly, Bee-eater nestlings are present underground for only a short period each year. Future research could therefore investigate whether the presence of sugar ant larvae coincides with the brooding of Bee-eaters, and report occurrences of sugar ants nesting in Bee-eater burrows. At Dryandra 59 Bee-eater nests were monitored, and only this one failed on account of the actions of any ant species. 2. 18/12/04 Greenslade’s Meat Ants attempted predation of one of two Common Bronzewing Phaps chalcoptera nestlings that fledged as I approached the nest. One fledgling flew out of sight and the other flapped to the ground near the nest. As I attempted to pick it up to replace it in its nest, hundreds of Greenslade’s Meat Ants swarmed onto my hand and the fledgling. The fledgling AUSTRALIAN 154FULTON FIELD ORNITHOLOGY was eventually returned to the nest safely, after the ants had been brushed off. The ants had gathered around the fledgling’s eyes, legs and on its soft fleshy cere, taking hold with their mandibles and contorting their bodies, apparently attempting to tear its flesh. Had the fledgling been left on the ground with the ants, they may have killed it. It remains to be established whether fledglings in similar situations can fend for themselves and survive, or whether the ants can kill them. 3. 15/12/02 A Common Quail Coturnix coturnix egg in an artificial ground nest was broken by a primary (i.e. initial) predator, with the yolk and most of the egg-white remaining. Greenslade’s Meat Ants ate the contents of the egg after the shell had been broken; that is, they were opportunistic secondary consumers. Although meat ants are well recorded as scavengers and detritivores in Australia (Read & Wilson 2004), there appears to be a dearth of information on their use of birds’ eggs. This observation indicates that they are interested in eggs. Broken and partially consumed eggs have been reported in many studies of nesting birds (e.g. Hobbs 1990; Picman 1992; Zannette 1997), indicating that ants would experience such events at natural nests. 4. 21/10/02 Greenslade’s Meat Ants killed two Yellow-plumed Honeyeater Lichenostomus ornatus nestlings 2–3 days from fledging. The Honeyeater nest was 3 m from the ground and hung in a cluster of leaves at terminal branches, as is typical for Yellow-plumed Honeyeaters (unpublished data). It was detected on 15/10/02 and monitored on 17, 19 and 21/10/02; the nestlings appeared in good health before being found mostly eaten away, with Meat Ants swarming over them, on 21/10/02. There had been three nestlings when last monitored, but only two carcasses were present on the last day; the missing nestling may have fallen out of the nest attempting to escape the ants, or may have been taken by another predator. Predation by Meat Ants is more likely than death by disease, because the nestlings appeared in good condition at each observation. My presence apparently did not cause the nest to be abandoned, because I had visited it three times previously and the adults had kept feeding the nestlings and gave no discernible reaction to me.