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Detection and assessment of the deeply buried high-grade uranium deposits in the Athabasca Basin rely on geophysical methods to map conductive rocks. Variable Quaternary surface cover can mask the anomalous signals from depth and affect the interpretation of inverted conductivity models. We present the analysis of several electromagnetic (EM) modeling studies and two field data sets to demonstrate the effects of varying Quaternary cover resistivity and thickness, on the ability to resolve the parameters of underlying sandstone, alteration, and basement conductors. Synthetic data, assuming a typical shallow EM sounding system and realistic resistivities found in the Athabasca Basin, indicate that resistivity and thickness parameters of the Quaternary cover can be separately recovered in cases in which this cover is more conductive than the underlying sandstone, but not when the cover is significantly more resistive. A 3D modeling study indicates that by using airborne EM data, it is possible to detect a basement conductor of 20 S at a depth of at least 600 m below the surface, even in the presence of Quaternary cover thickness variations of the up to 20% (40–60 m). Furthermore, although Quaternary cover variations and deeper sandstone alteration can produce comparable anomalous signal amplitudes in a time-domain EM response, their effects are most visible in distinctly separate time windows. Ground-penetrating radar and other data to characterize the Quaternary cover in the McArthur River area indicate that this cover consists mostly of sandy tills ranging in thickness from 0 to 117 m. Constrained 3D inversion of an airborne EM data set from the same area indicates basement conductors consistent with the depth and location of a known fault. Elevated conductivity in the sandstone by up to a factor of two over the background values could indicate possible alteration.

The nest of a Superb Lyrebird, in a spotted gum forest on the south-east coast of Australia, was monitored for approximately 10 weeks. The nest was discovered before the egg was laid, on June 16, 2020. The egg was laid on July 7, and the chick was taken by a Lace Monitor (Varanus varius) on August 29. A camera placed at the nest when discovered was active for the entire monitoring period. Thirteen sound recordings (in 6h periods) were made at the nest between July 16 and August 28 inclusive. The literature on vocalisations by the female lyrebird is scant, and in the light of our data, unrepresentative of her repertoire, especially during her role as parental carer. We present a series of photographs, sonograms and accessible sound recordings. These show specific behaviours of the female as she enters and leaves the nest, and the vocalisations specifically used when the female is approaching or leaving the nest, and when she is interacting with the egg, the chick and an intruder.

For most passerines, nest predation has a major impact on breeding success; however, information on the identity of nest predators is scant. In 2012, we investigated the identity of nest predators that each year depredate about 50% of the nests of 21 species in a south-east coastal bird community in New South Wales, Australia. The current study is a 2-year extension of this study and shows that at this study site (a) predation accounts for at least 90% of nest failures, (b) identified nest predators comprised two reptiles, nine birds and five mammals, (c) the suite of predators changes each season, (d) the two major predators were the Eastern Whipbird (Psophodes olivaceus) and the Fan-tailed Cuckoo (Cacomantis flabelliformis), (e) the impact of the Red Fox and Feral Cat was minimal, and (f) there was a variable and complex interaction between the parasitic cuckoos and their hosts. The data show definitively the overwhelming importance of nest predation on fledgling production, and bring to light new and important data on several aspects of the suite of nest predators.

The Fan-tailed Cuckoo Cacomantis flabelliformis inhabits thick forest, and nothing is known about how it finds the nests of its hosts, or whether it monitors the nests that it does find. We studied this cuckoo, and its hosts, for 8 breeding seasons between 2007 (August 2007–January 2008 inclusive) and 2014 (August 2014–January 2015 inclusive) on a 10-ha site in a coastal forest of south-eastern Australia, near Moruya, New South Wales. For three of these seasons, nests were monitored with cameras. The Cuckoo was recorded at the nests of only its four putative hosts at the site (White-browed Scrubwren Sericornis frontalis , Brown Thornbill Acanthiza pusilla , Superb Fairy-wren Malurus cyaneus and Variegated Fairy-wren M. lamberti ). It parasitised only the nests of the White-browed Scrubwren and Brown Thornbill, but it removed either eggs or young from all other nests at which it was recorded. There was no correlation between any measure of nest activity for a host species, and parasitism of that species, and cameras at nests recorded no evidence of nest monitoring by the Cuckoo. We conclude that individual Cuckoos may be hostspecific, and that the parasitism strategy is enigmatic, but is possibly haphazard and inefficient. As a result, the Fantailed Cuckoo finds most host nests too late for successful parasitism, it spoils them to re-instigate building, and is by default a major nest-predator.

SUMMARY VPem3D performs 3D inversion on time-integrated (resistive limit) data. Conversion to resistive limits delivers a massive increase in speed since the TEM inverse problem reduces to a quasi-magnetic problem. The time evolution of the decay is lost during the conversion, but the information can be largely recovered by constructing a starting model from CDIs or 1D inversions. We have carried out preliminary inversion of VTEM dBz/dt data from the Forrestania EM test range. The inversion places a weak conductor at a depth and location consistent with the known target. Run time is a few minutes, a fraction of that required by a full 3D EM inversion.

The goal of geophysical inversion of electromagnetic (EM) data is to recover a model of the geoelectrical properties of the sub-surface. The standard practice for 1D inversion of marine controlled source EM (CSEM) data is to generate smooth conductivity models using least squares (L2-norm) methods. However, sedimentary geology is stratified and piece-wise continuous. As such, smooth resistivity models cannot represent this character. In response to this inconsistency, a means was sought to generate more geologically plausible, piece-wise continuous models. The common approach in the literature when generating piece-wise continuous inversion models is to regularize L2-norm methods in such a manner as to induce blocky behaviour. Although effective, these techniques are self-conflictive; forcing non-smooth behaviour from an implicitly smooth algorithm. In contrast, L1-norm inversion inherently produces piece-wise continuous models. To investigate the possible utility of this approach, a L1-norm inversion algorithm has been developed and tested on synthetic and real datasets. The L1-norm results were compared with those generated using an industry standard L2-norm algorithm. The synthetic inversions focused on previously published examples. The real data inversions focused on electric and magnetic field measurements recorded over the main reservoir sand of the Pluto gas field in block WA350-P, North West Shelf, WA. The L1-norm inversions recovered, to within the resolution limits of the CSEM method, the depth, thickness and resistivity of the synthetic geological models and the Pluto-1 resistivity well log, whilst fitting the input data to within noise. When compared against the L2-norm profiles, the L1-norm inversion more closely represented the stratified character of the sedimentary sequence. It was therefore concluded that L1-norm inversion is an attractive alternative to smooth L2-norm methods when blocky inversion models are desired.

The flesh-footed shearwater (Puffinus carneipes) is a migratory seabird that ranges widely across the Pacific and Indian Oceans. The principal breeding populations are in Australia and New Zealand. The only breeding site in eastern Australia is on Lord Howe Island. Despite it being afforded a high level of legislative protection, the population on Lord Howe Island has declined substantially during the last few decades. The total extent of nesting habitat in 2002 was 24.3 ha, a reduction of 13.4 ha (35.6%) since 1978. Loss of nesting habitat was associated with increased urbanisation, the adverse impact of which extended beyond the footprint of buildings and gardens. In 2002, overall burrow density was 0.123 per m2 and the total number of burrows was estimated to be 29,853 ± 5867, a decline of about 19.0% since 1978. A substantial decline in burrow density was evident in the colony where loss of habitat to urbanisation had been greatest. In 2002, 58% of burrows were occupied by breeding birds, and the total population size was estimated to be 17,462 breeding pairs. Breeding success (the proportion of eggs that produced fledglings) was 50%, but was lowest in the most urbanised colony. To avert further declines in the population of flesh-footed shearwaters on Lord Howe Island major changes in land use practices, enforced through appropriate legislation, are needed, together with reductions in the level of seabird bycatch in fisheries operations and in the amount of plastics that litter the world’s oceans.

Here we document the removal of eggs from the nests of two passerine species—Brown Thornbill Acanthiza pusilla and Yellow-faced Honeyeater Caligavis chrysops —by Eastern Spinebills Acanthorhynchus tenuirostris .

Both domestic and wild-type European Rabbits Oryctolagus cuniculus (L.) have been liberated on islands all over the world for a variety of reasons: for sport, to farm for meat or fur, as food for other animals or bait for lobster pots, to control vegetation, amuse tourists, and even to conserve representative populations from myxomatosis. Results of these introductions have likewise varied, from complete failure to densities so high as to denude completely the island of vegetation and soil. Some interesting populations have survived remarkably adverse conditions for up to 100 years before becoming extinct. Others provide natural experiments on the effects of introduced predators, competitors, or diseases like myxomatosis. We list 800 islands or island groups on which Rabbits have been liberated, giving name, location, latitude and longitude, and area, followed by date of introduction, type of rabbit, population changes, present status, and effects of the Rabbits on their environment. For many islands information is still meagre or completely lacking; we hope that this provisional list will stimulate readers to send us additions and corrections, or to publish the data themselves.

Gradiometry has come of age in the past decade, with the development of airborne systems capable of measuring full gravity and magnetic gradient tensors. Airborne gravity gradiometry in particular represents a stunning technical achievement, delivering a completely new capability to exploration. Gravity gradients can now be acquired rapidly in remote and inaccessible areas. Airborne magnetic gradiometry has been available for many years, albeit for a limited number of components. Full tensor magnetic gradiometry is a very recent development. There are several technical advantages of gradiometry, including interpolation between lines and, for magnetics,suppression of diurnal effects, potential for characterisation of remanence, and (for the theoretically minded) the satisfaction of dealing with true potential fields. In terms of interpretation, gradiometry offers greater sensitivity to the near-surface than conventional gravity or magnetics. This is a blessing for resolution of shallow structure and stratigraphy, and for definition of outcropping or sub-cropping targets, e.g. kimberlites. However, enhancement of shallow features can be a disadvantage in exploration for buried targets. The problem is compounded by the inherent variability of the shallow sub-surface, owing to weathering and to transported cover. Finally, sensitivity to the near-surface also implies sensitivity to topography and flying height. This paper explores these issues and others arising during geologically-constrained inversion of gradiometer data. Analysis of gradiometer data alone is not sufficient to fully prescribe the sub-surface distribution of density or susceptibility: acquisition of full tensor data does not deliver us from non-uniqueness. Geological and petrophysical information, primarily derived from drill holes, is required to reduce uncertainty in interpretation. In order to capture both geology and physical properties, a model must be both categorical and quantitative. Such ‘geo-physical’ models are a force for integration in their own right, and also offer a number of practical advantages over pure property models. In particular, geological boundaries can be recognised, and therefore modified (subject to drill hole pierce point constraints); thus, when applied to a geological model, inversion can adjust its geometry as well as its density or susceptibility distribution.

We have analysed 1,169 nest records for the Welcome Swallow Hirundo neoxena. The data were obtained predominantly from south-eastern Australia during the period 1964 to 1976. Information on the nest, nest site, laying, clutch size, incubation, nestling period, breeding success and breeding season is presented. Breeding is similar to that of the northern hemisphere Barn Swallow H. rustica. However, clutch size is distinctly smaller than for Barn Swallows in Britain and there was no evidence that clutch size increases with latitude, but some that suggests that it did so inland. Welcome Swallows in Australia are less successful (young fledged from eggs laid) than Barn Swallows in Britain.

Four skins of Nesoclopeus poeciloptera (Hartlaub) from Fiji and two previously unknown skins of Tricholimnas lafresnayanus (Verreaux & de Murs) from New Caledonia held in collections in Sydney, Australia, are listed. We have examined a total of twelve T. lafresnayanus in world museums. Two others have been traced and a third possibly exists. Two more have been destroyed. Measurements from this rail and its plumage are compared with those from the Woodhen T. sylvestris (Sclater) of Lord Howe Island and their similarities emphasized.