Corvus Coronoides Research Articles

Non-Lethal Dose-Response Models Replace Lethal Bioassays for Predicting the Hazard of Para-Aminopropiophenone to Australian Wildlife.

Para-aminopropiophenone (PAPP) is a potent methaemoglobin (MetHb) forming agent used for the lethal control of exotic carnivores and mustelids. To assess the sensitivity of Australian wildlife to PAPP we developed an in vivo assay that did not use death as an endpoint. Sub-lethal dose-response data were modelled to predict PAPP doses required to achieve an endpoint set at 80% MetHb (MetHb80). The comparative sensitivity of non-target mammals referenced to this endpoint was found to be highly variable, with southern brown bandicoots (Isoodon obesulus) the most sensitive species (MetHb80 = 6.3 mg kg-1) and bush rats (Rattus fuscipes) the most tolerant (MetHb80 = 1035 mg kg-1). Published LD50 estimates were highly correlated with PAPP doses modelled to achieve the MetHb80 endpoint (r2 = 0.99, p < 0.001). Most dose-response data for native mammals were collected in the field or in semi-natural enclosures, permitting PAPP and placebo dosed animals to be fitted with tracking transmitters and transponders and released at their point of capture. A protracted morbidity and mortality was observed only in Australian ravens (Corvus coronoides). The combination of sub-lethal dose-response assay and survival data collected in the field provided more relevant information about the actual hazard of pest control agents to non-target wildlife species than laboratory-based lethal-dose bioassays. We discuss the need to replace lethal-dose data with biologically meaningful insights able to define a continuum of toxicological hazards that better serve the needs of conservation and veterinary scientists and wildlife managers.

Interacting impacts of drought and fire on bird populations—insights from a long-term study in the Warrumbungles

ABSTRACT The interacting effects of drought and fire on ecological communities are poorly understood. Long-term studies in the Warrumbungle Mountains, central-west New South Wales, subject to drought and fire during the past 21 years, enabled their separate and combined effects to be quantified for individual species and functional groups. Insectivores (especially ground-foragers) dominated previous lists of declining species in this region of NSW and were also prominent in the present work. Insectivores were more likely to be drought- than fire-affected, with seven species declining due to drought, three to drought plus fire, and three to fire alone. Our analyses also revealed declines in a suite of honeyeaters (Meliphagidae), previously not reported as declining. Honeyeaters are major pollinators of eucalypts, so the loss of nectarivores and insectivores has far-reaching implications for pollination, recruitment, successional dynamics, and forest health. Four honeyeater species were adversely affected by drought, five by fire, and one by a combination of drought and fire. Drought and fire, alone or in combination, were implicated in declines of granivores, including the Crimson Rosella Platycercus elegans, and frugivores, especially the Mistletoebird Dicaeum hirundinaceum, the latter reflecting the loss of mistletoes in fire-affected landscapes, and foreshadowing additional losses due to the reliance on mistletoe by many species. Another group not previously identified as threatened, but declining due to drought were two omnivores, the Pied Currawong Strepera graculina and Australian Raven Corvus coronoides. Hollow-nesting birds including two species of treecreeper and the Laughing Kookaburra Dacelo novaeguineae fared badly. Several common Australian species were among the decliners, including Laughing Kookaburra, Willie Wagtail Rhipidura leucophrys and Australian Magpie Cracticus tibicen. We conclude that no suite of birds is exempt from these environmental stressors, and predict that, as droughts reduce populations at regional scales and fires diminish carrying capacity of critical habitats at landscape scales, rarer species will decline to local extinction while more commonly observed species will be reduced in abundance.

Morphological and molecular description of a new species of Isospora (Apicomplexa) from a New Holland honeyeater (Phylidonyris novaehollandiae).

A new Isospora species is described from New Holland honeyeaters (Phylidonyris novaehollandiae). Sporulated oocysts (n=25) were characterised as subspheroidal, 29-32×28-31 (29.8×29.4); length/width (L/W) ratio 1.01-1.02 (1.01). Wall bi-layered, 1.3-1.6 (1.5) thick, outer layer smooth, c.2/3 of total thickness. Micropyle and oocyst residuum absent, but usually two polar granules are present. Sporocysts (n=25) ovoidal, 18-19×12-14 (18.4×12.3); L/W ratio 1.42-1.53 (1.50). Stieda body present, flattened, c.0.5 deep × 2.5 wide; sub-Stieda present, rounded, c.2.5 deep × 3.5 wide; para-Stieda body absent; sporocyst residuum present, usually a distinctly irregular body consisting of numerous small granules that appear to be membrane-bound. Sporozoites vermiform, with robust anterior and posterior refractile bodies. Molecular characterization was conducted at the 18S and 28S ribosomal RNA and the mitochondrial (mt) cytochrome oxidase (COI) loci. Phylogenetic analysis of genomic 18S and mt COI sequences indicated that Isospora phylidonyrisae n. sp. was genetically similar to Isospora coronoideae, isolated from an Australian raven (Corvus coronoides) in Western Australia, with a 99.3% and 98.4% homology, respectively. The 28S rRNA sequence was most similar to Isospora anthochaerae (KF766053) and Isospora manorinae (KT224381), both with a 98.2% genetic similarity. Based on morphological and genetic data, this isolate is a new species of Isospora, which is named Isospora phylidonyrisae n. sp. after its host.

Efficacy and risks from a modified sodium nitrite toxic bait for wild pigs.

Wild pigs (Sus scrofa) are a destructive invasive species throughout many regions of the world. In 2018, a field evaluation of an early prototype of a sodium nitrite (SN) toxic bait in the United States revealed wild pigs dropped large amounts of the toxic bait outside the pig-specific bait stations while feeding, and thus subsequent hazards for non-target animals. We modified the SN-toxic bait formulation, the design of the bait station, and the baiting strategy to reduce dropped bait. We tested the modifications in Queensland, Australia (December 2018), Alabama, USA (August 2019), and Texas, USA (March 2020) under differing climatic and seasonal conditions for one night. Cumulatively we found 161 carcasses of all age classes of wild pigs using systematic transects. Remote camera indices indicated high lethality for wild pigs, achieving population reductions of 76.3 to 90.4%. Wild pigs dropped only small particles of SN-toxic bait (average = 55.5 g per bait site), which represented a 19-fold decrease from the previous trial. Despite this reduction, we found three Australian ravens (Corvus coronoides) in Queensland, two Virginia opossums (Didelphis virginiana) in Alabama, and 35 granivorous-passerine birds (mostly dark-eyed juncos [Junco hyemalis]) in Texas dead from consuming the dropped bait. We did not detect any population-level effects for those species. Our modifications were effective at reducing populations of wild pigs, but the deaths of non-target species require further steps to minimize these hazards. Next steps will include evaluating various deterrent devices for birds the morning after SN-toxic bait has been offered. Published 2020. This article is a U.S. Government work and is in the public domain in the USA.

Inferred predation of Fairy Tern eggs by Ruddy Turnstones at Rottnest Island, Western Australia, an internationally significant shorebird site

Ruddy Turnstones Arenaria interpres have been identified as egg-predators at seabird and shorebird colonies, including gull and tern colonies in the tropics and Northern Hemisphere. The Australian Fairy Tern Sternula nereis nereis is a threatened (Environment Protection and Biodiversity Conservation Act 1999: Vulnerable) coastal seabird, whose breeding behaviour and ecology expose it to a wide range of threats. This study describes inferred predation on Fairy Tern eggs at a small breeding colony on Rottnest Island, Western Australia, by Ruddy Turnstones, a previously unsuspected predator for thisspecies. Unlike the behavioural response shown towards Silver Gulls Larus novaehollandiae and Australian Ravens Corvus coronoides, which includes collective group defence and dive-bombing, Fairy Terns showed a lack of aggression towards Turnstones within the colony. The lack of a behavioural response suggests that the Terns did not recognise the Turnstones as predators, which may increase the risk of egg-predation. This study suggests that we should be alert to threats from unsuspected predators, which have the potential to reduce the breeding success of this Vulnerable tern.

Repetitive confrontations between Australian Ravens (Corvus coronoides) and lone Australasian Darters (Anhinga novaehollandiae)

Aggressive confrontations between different species of birds are commonly reported in scientific literature. In particular, the Australian Raven (Corvus coronoides) engages in confrontations with other birds, including competitions for food resources, kleptoparasitism, nest defense, and retaliation against mobbing birds. Herein, I report repeated observations of multiple ravens staging confrontations against lone Australasian Darters (Anhinga novaehollandiae) in an urban park in Sydney, Australia. During these confrontations, ravens enclosed around the darters and both species exhibited bill gaping and snap-threats. In some confrontations, ravens divebombed the darters from behind. These behaviors are found in scientific literature for each species, respectively; however, the motivation behind these confrontations was not clear.

Uptake of ‘Eradicat’ feral cat baits by non-target species on Kangaroo Island

Abstract ContextPredation by feral cats (Felis catus) threatens a range of vertebrate species across Australia, and cat-free islands increasingly act as safe havens for biodiversity. A feral cat eradication program has begun on Kangaroo Island (4405km2) in South Australia, and poison baiting is likely to be one of the main methods used. Aims Here, we trial a non-toxic version of a cat bait, ‘Eradicat’, on western Kangaroo Island, to examine its potential impact on non-target species. MethodsNon-toxic baits containing the biomarker Rhodamine B were deployed across four sites in early August and late November in 2018, with bait take and consumption assessed both by remote cameras and by the presence of Rhodamine B in mammalian whisker samples taken post-baiting. Key resultsCats encountered baits on very few occasions and took a bait on only one occasion in August (&amp;lt;1% of 576 baits deployed). Non-target species accounted for over 99% of identifiable bait takes. In both seasons, &amp;gt;60% of all baits laid was taken by either the common brushtail possum (Trichosurus vulpecula), bush rat (Rattus fuscipes) or Australian raven (Corvus coronoides). In November, Rosenberg’s goanna (Varanus rosenbergi) and southern brown bandicoot (south-eastern subspecies; Isoodon obesulus obesulus), listed nationally as Endangered, also took baits (3% and 1% respectively). The Kangaroo Island dunnart (Sminthopsis fuliginosus aitkeni), listed nationally as endangered, approached a bait on only one occasion, but did not consume it. Evidence of bait consumption was visible in the whiskers of captured common brushtail possums (100% of post-baiting captured individuals in August, 80% in November), bush rats (59% in August and 50% in November), house mice (Mus musculus) (45% in November) and western pygmy-possums (Cercartetus concinnus) (33% in November). ConclusionsAlthough feral cat baiting has the potential to significantly benefit wildlife on Kangaroo Island, impacts on non-target species (particularly the bush rat and common brushtail possum) may be high. ImplicationsAlternative cat baits, such as those containing a toxin to which native species have a higher tolerance or that are less readily consumed by native wildlife, will be more appropriate.

Isospora coronoideae n. sp. (Apicomplexa: Eimeriidae) from the Australian raven (Corvus coronoides) (Passeriformes: Corvidae) (Linnaeus, 1758) in Western Australia.

A new Isospora (Apicomplexa: Eimeriidae) species is described from an Australian raven (Corvus coronoides) in Western Australia. Sporulated oocysts (n = 21) are ovoid, 21.2 (18.4-23.9) μm in length and 18.8 (16.9-20.6) μm in width, with a shape index of 1.13. The bi-layered oocyst wall is smooth and colourless, 1.2μm thick. A polar granule and oocyst residuum is present, but the micropyle is absent. The sporocysts are ovoid-shaped, 16.3 (13.7-18.9) × 10.7 (8.4-12.9) μm, with a shape index (length/width) of 1.52. Stieda and substieda bodies are present, the Stieda body being small and hemidome-shaped and the substieda being indistinct. Each sporocyst with four vermiform sporozoites arranged head to tail. The sporozoites are crescent-shaped, 9.0 (8.9-9.2) × 2.7 (2.3-3.0) μm, with a shape index (length/width) of 3.33. The sporocyst residuum is present. The isolated oocysts had different morphological characteristics when compared with all known Isospora spp. The coccidian parasite was analysed at the 18S and 28S ribosomal RNA and the mitochondrial cytochrome oxidase (COI) loci. At the 18S locus, I. coronoideae n. sp. exhibited 98.9% similarity to I. neochmiae from a captive-bred red-browed finch (KT224380) and Isospora sp. from domestic pigeons (Columba livia domestica) (AB757860), 98.5% similarity to I. gryphoni (AF080613) from an American goldfinch and 98.3% similarity to I. manorinae (KT224379) from a yellow-throated miner. At the 28S locus, it exhibited 95.4% and 94.8% similarity to I. manorinae (KT224381) and I. anthochaerae (KF766053), respectively. At the COI locus, it exhibited 99.8% and 99.7% similarity to I. butcherae (KY801687) and I. neochmiae (KT224378), respectively. Based on morphological and molecular data, this isolate is a new species of Isospora, which is named Isospora coronoideae n. sp. after its host, the Australian raven (Corvus coronoides) (Passeriformes: Corvidae) (Linnaeus, 1758).

Predation of a Buff-banded Rail Hypotaenidia philippensis by Australian Ravens Corvus coronoides on Penguin Island, Western Australia

Australian Ravens Corvus coronoides , although primarily scavengers, are known to prey on large vertebrates, which can detrimentally affect the prey populations. This paper describes an Australian Raven attacking and killing a Buffbanded Rail Hypotaenidia philippensis on Penguin Island, Western Australia, in the presence of several other Ravens.

IInteractions between Australian Ravens and raptors in a pastoral area of New South Wales: Interspecific aggression and nest-site spacing

This study, near Tamworth, New South Wales, investigated the interactions within a diurnal raptor and Australian Raven Corvus coronoides community. The Australian Raven (hereafter ‘Raven’) is an abundant breeding resident here, is the only corvid that breeds in the area, and is known to have a close association with many raptor species. It is known to interfere with nests, provide frequent harassment and decrease the breeding productivity of several nesting raptor species, yet few studies have been completed on this issue, and its significance remains unknown. The abundance of raptors and Ravens and diversity of raptor species were determined from weekly surveys along a fixed 60-km transect in autumn to late spring 2016. A negative association was found between raptor species diversity and Raven abundance. The density and distribution of active or potential raptor and Raven nests were also recorded along the transect: active raptor nests had significantly more active stick nests of other species (raptors and Ravens) nearby (within 500 m), whereas active Raven nests had fewer such active nests within 500 m. Intruding Ravens and Wedge-tailed Eagles Aquila audax elicited significantly higher rates of defensive interactions from nesting Black Falcons Falco subniger than did other diurnal raptor species; Ravens triggered the highest rate of response. An increased understanding of the factors responsible for shaping community structure is useful for the management of threatened species. The raptor assemblage around Tamworth includes five threatened species, at least four of which are known to breed there, making competition for nest-sites here worthy of research.

Bad news for bobtails: understanding predatory behaviour of a resource-subsidised corvid towards an island endemic reptile

Context Resource subsidisation as a result of urbanisation and other human activity can have positive impacts for some opportunistic predators. Many species of corvid have benefitted from the expansion of human-dominated habitats; however, their impacts on co-occurring prey fauna are generally poorly understood. Aims We aimed to test the hypothesis that urbanisation associated with tourism impacts the predator–prey relationship between Australian ravens, or wardongs (Corvus coronoides), a ubiquitous corvid of southern Australia, and Rottnest Island bobtails (Tiliqua rugosa konowi), a subspecies of bobtail lizard isolated to a small (19km2) island off the coast of Western Australia. Methods Using clay model lizards and camera traps, we assessed the wardongs’ attack rates by distance from the settlement and by whether the model was in closed or open habitat. Key Results We found that while wardongs preyed upon Rottnest Island bobtails, predation was not affected by proximity to human settlement despite the highest number of wardongs being found there. Models in closed vegetation were attacked by wardong significantly more than were those in open vegetation. Implications Increased predation rates in closed vegetation suggests that current revegetation efforts on the island may be increasing the availability of preferred hunting habitat for the wardong. This finding may influence decisions by management on whether to control the large population of wardongs on the island.

The first complete mitochondrial genome sequence of an Australian raven (Corvus coronoides)

Here, we report the complete mitochondrial genome of an Australian raven (Corvus coronoides). The mitogenome of C. coronoides was characterised as a circular molecule of 16,925 bp in length encoding a typically conserved structure similar to those of other Corvidae. It consisted of 13 protein-coding genes (PCGs), two rRNA genes, and 22 tRNA genes, with all protein-coding sequences commencing with methionine. The lengths of 12S ribosomal RNA and 16S ribosomal RNA were 980 bp and 1600 bp, respectively, and were located between tRNA-Phe and tRNA-Leu. The overall base composition of the mitogenome of C. coronoides was slightly higher AT (56.0%) content than GC (44.0%). A phylogenetic tree using available complete mitogenome sequences of the family Corvidae revealed a close evolutionary relationship of C. coronoides with the now extinct Chatham raven (C. moriorum), a large songbird that was native to the Chatham Islands east of New Zealand.

Killing of a mobbing Crested Pigeon Ocyphaps lophotes by an Australian Raven Corvus coronoides

Mortality in birds engaged in mobbing potential predators is rare, especially while defending their progeny. This paper reports an incident of a nesting Crested Pigeon Ocyphaps lophotes being fatally attacked by an Australian Raven Corvus coronoides that it was mobbing. The Raven remained on the carcass for some time, but did not feed on it.

Killing of a mobbing Crested Pigeon Ocyphaps lophotes by an Australian Raven Corvus coronoides

Mortality in birds engaged in mobbing potential predators is rare, especially while defending their progeny. This paper reports an incident of a nesting Crested Pigeon Ocyphaps lophotes being fatally attacked by an Australian Raven Corvus coronoides that it was mobbing. The Raven remained on the carcass for some time, but did not feed on it.

The origin and phylogenetic relationships of the New Zealand ravens

The relationships of the extinct New Zealand ravens (Corvus spp.) are poorly understood. We sequenced the mitogenomes of the two currently recognised species and found they were sister-taxa to a clade comprising the Australian raven, little raven, and forest raven (C.coronoides, C. mellori and C. tasmanicus respectively). The divergence between the New Zealand ravens and Australian raven clade occurred in the latest Pliocene, which coincides with the onset of glacial deforestation. We also found that the divergence between the two putative New Zealand species C. antipodum and C. moriorum probably occurred in the late Pleistocene making their separation as species untenable. Consequently, we consider Corax antipodum (Forbes, 1893) to be a subspecies of Corvus moriorum Forbes, 1892. We re-examine the osteological evidence that led 19th century researchers to assign the New Zealand taxa to a separate genus, and re-assess these features in light of our new phylogenetic hypotheses. Like previous researchers, we conclude that the morphology of the palate of C. moriorum is unique among the genus Corvus, and suggest this may be an adaptation for a specialist diet.

Forensic genetic evidence of beak and feather disease virus infection in a Powerful Owl, Ninox strenua

Beak and feather disease virus (BFDV), which causes psittacine beak and feather disease (PBFD), is known to infect a wide range of bird species, with all members of the Psittaciformes recognised as being susceptible. Across the world, genetically distinct circovirus species cause feather disease akin to PBFD in the Australian Raven (Corvus coronoides), as well as a wide range of columbids, anatids and lariids. Until recently, BFDV was thought to be restricted to Psittaciformes, with a rich viral genetic diversity present in parrots and their allies throughout Australia. The possibility of rare spill-over infection of BFDV into non-psittacine birds has the potential to reveal insights into the disease ecology of PBFD and the ontology of BFDV. In this paper we report evidence of BFDV infection in a Powerful Owl (Ninox strenua), which had feather lesions characteristic of PBFD. Analysis of the BFDV genome associated with the infection revealed lorikeets, which are known prey items of Powerful Owls, to be a likely source.

Kleptoparasitism of Australian Magpie by Australian Ravens

This note reports an observation of apparent kleptoparasitism by Australian Ravens Corvus coronoides . Such behaviour has rarely been recorded for Australian Ravens or other Australian corvids.

The role of motor diversity in foraging innovations: a cross-species comparison in urban birds

The capacity to behave innovatively facilitates adaptation to changing environmental conditions and accelerates speciation rates. Innovation tendencies show substantial variation both among and within species, but the sources of this variation remain poorly understood. There has been much debate on the role of cognition and significant amounts of empirical research on the influence of motivational and state-dependent processes, but the prediction that innovation might also be facilitated by motor processes has only recently begun to gain traction. Here, we measured innovative foraging in 7 common urban avian species under free-ranging conditions and explored the role of motor flexibility as well as several potential other predictors of innovation such as motivation and morphology. Species differed significantly in their tendency to forage innovatively, with a true corvid, the Australian raven, Corvus coronoides, outperforming all other species. Across species, motor flexibility was the strongest predictor of the capacity to forage innovatively. Our results extend previous work demonstrating the role of motor diversity in individual differences in the tendency to forage innovatively and provide the impetus for future research on links between motor and cognitive flexibility.

Carrion subsidies provided by fishermen increase predation of beach‐nesting bird nests by facultative scavengers

AbstractMany predators are also scavengers that feed on carrion and human refuse. Therefore, the availability of carrion can elevate the abundance or activity of facultative scavengers, amplifying predation pressure on prey. On Australian beaches, fishermen often discard fish carcasses that could attract facultative scavengers, both native, such as Australian ravens Corvus coronoides, and invasive, such as European red foxes Vulpes vulpes, and result in elevated rates of predation on wildlife. We tested whether the presence of fish carcasses increased the risk of depredation for nearby nests of beach‐nesting birds by deploying artificial nests in 12 subsidized and 12 control patches, spaced 1 km apart, on a beach. We placed a fish carcass in each subsidized patch, but not at control patches. In each patch, we placed two artificial nests, which resembled red‐capped plover Charadrius ruficapillus nests, 80 m apart and 40 m from carcasses at subsidized patches. Nest predators were identified from tracks and predator activity near subsidized and control nests was measured by counting tracks crossing a straight transect (220 m). The activity of a native predator, the Australian raven, was 17 times higher near (&lt;80 m) nests with fish carcasses than nests without carcasses. After 72 h, 96% of nests near carcasses were depredated compared with 30% of nests without carcasses. Ravens were identified as the culprit for 80% of depredated nests. Although other predators were present in the study area, they did not depredate artificial nests in this experiment. Previous studies have highlighted the effects of permanent and/or large‐scale food resources on scavenger abundance and impact. A key management implication of our study is that even small, sparsely distributed, temporally irregular food subsidies, provided by humans, can elevate the activity and predatory impacts of facultative scavengers.

A successful long-distance aerial pursuit of an Australian Raven Corvus coronoides by a Brown Goshawk Accipiter fasciatus

The Brown Goshawk Accipiter fasciatus has a variable diet comprising mainly avian prey and mammals, and most observations suggest that it employs a range of ambush tactics but rarely uses long-distance aerial pursuits. Here I document a rare instance of a successful long-distance aerial pursuit of an Australian Raven Corvus coronoides by a Brown Goshawk, on 29 March 2015, on Broughton Island, New South Wales. After multiple unsuccessful aerial attacks, the Goshawk eventually succeeded. Although corvids are abundant and widespread throughout Australia and are within the preferred avian prey size range, they are rarely observed in the Goshawk’s diet. Two ecological factors probably contributed to this observation: (1) there is little woodland here and thus little concealment for ambush tactics and (2) prey availability on Broughton Island and the surrounding islands has been altered by programs to eradicate pest mammals, thereby limiting the prey available to this species in this area.