Justification of Red List Category
This species has been up-listed to Vulnerable because the species eastern range appears to be rapidly retracting north and it is contested that three sub-populations, each containing less than 1000 individuals, remains valid. Further, it is arguable that the entire population remains below the critical threshold of 1000 individuals with large areas suspected to be undergoing continued habitat clearance and degradation.
Because of its inconspicuousness, it is difficult to estimate the size of the population anywhere within the species range. Consequently we can only be confident in population estimates for just two regions: the Tiwi Islands where there are c.100 (unlikely to be isolated but probably a separate subpopulation) and SE Qld/ NE NSW where there are c.0. The loss of the South-east Queensland population (10-30 pairs) reduces previous population estimates in Queensland to up to 125 pairs. Considering the unknowns around these estimates, combined with a paucity of knowledge on current population trends in most regions, an estimated population size of <500 pairs appears more likley than the 700 pairs estimated in Garnett et al. 2011 (Seaton, R. in litt. 2016).
The population may be declining owing to habitat loss in at least eastern Queensland; the rate of decline has not been quantified but is not suspected to be rapid (Garnett et al. 2011).
Erythrotriorchis radiatus is endemic to Australia. Historically, it ranged in northern and eastern Australia, north of c.33°S in the east, and 19°S in the west, but its range has contracted in the east and it is now considered at least functionally extinct in New South Wales and South-east Queensland (Cooper et al. 2014 and Seaton 2014). The full extent of the retraction in range up the East coast is currently unknown (Seaton 2014), but no breeding records are currently known from south of Cape York. The population was estimated at only 330 pairs in the early 1990s, but estimates were revised to 700 pairs in 2011 due to a suspected underestimate of nesting densities (Garnett et al. 2011). However, a current paucity of knowledge of the Western Australia and Northern Territory populations, coupled with increasing concern over habitat fragmentation and degradation across their range, brings this upwards revision into question. Consequently, a precautionary estimate of less than 500 pairs, including 100 pairs on Tiwi Islands and up to 125 pairs in Queensland appears reasonable. Further, it remains unclear whether breeding is continuous from Queensland across the Gulf into northern Australia (Czechura et al. 2011), thus although the populations are unlikely to be entirely isolated, treating them as separate subpopulations is warranted. It is therefore contested that there are three sub-populations, each containing less than 1000 individuals (Tiwi Islands, Top end & Queensland) (R. Seaton in litt. 2016).
It lives in coastal and subcoastal, tall, open forests and woodlands, tropical savannas traversed by wooded or forested rivers and along the edges of rainforest. It builds stick nests in trees taller than 20 m within 1 km of a watercourse or wetland. It hunts in open forests and gallery forests, with a home range of up to 290 km2, taking mostly medium to large birds, but also snakes. In winter in eastern Australia, it appears to move from nest-sites in the ranges to coastal plains, where it often feeds on waterbirds taken from open wetlands. A study of Red Goshawk pairs in Kakadu National Park found the female to tend to the nest for 81% of the time, whilst males did not incubate (Debus et al. 2015). Recent evidence suggests that juveniles can disperse up to 400km from the nest (R. Seaton in litt. 2016).
Widespread clearance for agriculture probably caused the historical decline in north-eastern New South Wales and southern Queensland. Continuing clearance is affecting more northerly populations. Even if riparian strips are left uncleared, pairs usually nest in the tallest trees that are then exposed to storm damage and other disturbance. Clearing of forest for acacia plantations has rendered some territories on Melville Island unproductive (S. Garnett in litt. 2007). Egg-collecting may result in the failure of some nests as does the burning of nest trees or disruption of breeding by fire. Inappropriate fire regimes causing the thickening of vegetation is also considered a threat (Red Goshawk Recovery Team in litt.). Shooting by pigeon and poultry owners, and possibly pesticides, causes some mortality of individuals and may result in temporary local scarcity. Prey abundance may be reduced by loss or degradation of freshwater wetlands, loss of hollow-bearing trees in which prey breed, over-grazing by livestock and feral herbivores, and changed fire regimes.
Conservation Actions Underway
CITES Appendix II. Some survey work has been carried out in various parts of the species's range. The Red Goshawk Recovery Team is developing a plan to address actions in National Recovery Plan, including: establishing a central data-base of all records for the species, map essential habitat across the species whole range and determining mainland habitat-use and home-range patterns (Red Goshawk Recovery Team in litt.)Conservation Actions Proposed
From Garnett et al. (2011) & DERM (2012). Study demography, especially adult survivorship. Identify important populations and monitor key indicator sites. Investigate the impact of habitat fragmentation and fire regimes on the spatial distribution of nesting pairs, their productivity and the abundance of prey. Protect habitat through purchase or voluntary conservation agreements. Encourage landholders to protect and manage Red Goshawk territories. Promote information used to identify and protect nesting habitat. Improve knowledge of ecological requirements (e.g. habitats critical for survival) to more clearly inform management. Produce educational materials that promote the recovery process. Limit access to known nest sites.
45-60 cm. Large, powerful, reddish-brown hawk. Adult has pale, dark-streaked head, two-tone underwing, rufous lesser and median coverts, with the remainder white with black barring. Adult male has rufous underbody. Adult female much paler and heavily streaked with black. Juvenile has rufous head. Similar spp. Distinguished from other raptors by boldly scalloped rufous upperparts and thighs, conspicuous on birds flying away from observer. Voice Variety of cries and chattering calls. Males are said to sound peevish and wheezy, females harsh and strident. Hints Search in open forest and woodlands, especially near rivers, in Top End and Kimberley regions.
Text account compilers
Benstead, P., Garnett, S., McClellan, R., Stattersfield, A., Symes, A., Taylor, J., North, A.
Seaton, R., Garnett, S., Baker-Gabb, D.
BirdLife International (2020) Species factsheet: Erythrotriorchis radiatus. Downloaded from http://www.birdlife.org on 27/05/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 27/05/2020.