Justification of Red List Category
This species has been uplisted to Vulnerable because it is suspected to have undergone rapid declines over the past three generations (17 years), owing to a combination of changed fire regimes and introduced predators: anthropogenic fires occurring over increasingly large scales often remove cover for the species, rendering it more vulnerable to multiple predators, particularly feral cats. Such increasingly severe fires, in many places fuelled by introduced invasive pasture grasses, probably also change habitat suitability and resource availability.
The population of G. s. smithi was estimated at c120,000 mature individuals in 2010, based on an AOO of 6,000 km2 and a density of 0.2 birds/ha, while G. s. blaauwi was estimated at 6,000 mature individuals in 2010 based on 0.1 birds/ha in occupied habitat (Garnett et al. 2011), giving a total population estimate of 126,000 mature individuals (Garnett et al. 2011). These may well be marked over-estimates. Woinarski et al. (2012) calculated a mean abundance of 0.05 (based on tallies of no. of birds seen in 8 visits to a 1 ha quadrat, so effectively a density of 0.006 birds/ha) across 136 sampled plots in Kakadu NP, a stronghold for this species. Woinarski et al. (2012) also reported a statistically significant 79% decline in abundance across these monitoring plots from the period 2001-04 to 2007-09, although the species was reported originally in relatively few plots, so the decline estimate is not very robust.
Populations in Kakadu have declined substantially over the last decade based on a decline in relative abundance from 0.24 in 2001-2004 to 0.05 in 2007-2009 (Woinarski 2009, in Garnett et al. 2011), while the population on the Tiwi Islands may have declined as a result of clearance for forestry. G. s. blaauwi is now extremely scarce in the eastern half of its former range. At Kalumburu, where it was historically very numerous, only 1 pair was found in searches during 1999 (Garnett and Crowley 2000), and it was reported to have declined dramatically in the Mitchell Plateau region (Department of Sustainability, Environment, Water, Population and Communities 2011). The overall population is suspected to be undergoing a rapid decline over three generations (17 years).
Geophaps smithii is endemic to Western Australia and Northern Territory, Australia. The nominate subspecies has declined or disappeared from the west, east and south parts of its distribution, over the last 100 years. It is now only found in about half of its former range, in sub-coastal north Northern Territory. G. s. smithi was estimated to number c120,000 mature individuals (with low reliability) in 2010 (115,000 in the mainland subpopulation and 5,000 on the Tiwi Islands) (Garnett et al. 2011, Woinarski in litt. 2016). Subspecies blaauwi is recorded from remote areas of the north-west Kimberley region, northern Western Australia. However, there are few recent records, including from Kalumburu where it was common in the 1970s. G. s. blaauwi was estimated to number 6,000 mature individuals (with low reliability) in 2010 (Garnett et al. 2011, Woinarski in litt. 2016). Both subspecies are thought to be declining, with rapid declines in relative abundance at several monitored sites (Garnett et al. 2011), although there is no substantial ongoing monitoring across most of the species’ range.
The western subspecies blaauwi occurs primarily in open woodland, particularly between the rugged King Leopold Sandstones and alluvial flats. The eastern subspecies smithii primarily inhabits open forest and woodland dominated by Eucalyptus tetrodonta and E. miniata that has a structurally diverse understorey, usually in areas with a fire regime that promotes a mosaic of fire ages, including wet season burns, which promote grass diversity and year-round seed availability (Fraser et al. 2003). The ground cover is mostly tall grasses, though the pigeons are usually seen feeding in recently burnt areas, by roads and in short grass (Johnstone 1981, in Garnett et al. 2011). It appears to rely on perennial grass species which set seed relatively early (Fraser 2001). Breeding takes place in the dry season, between March and October, and it usually lays 2 eggs in rudimentary nests made on the ground, most often at the base of a clump of grass. It feeds on seeds taken from bare ground. It may benefit from the recent spread of introduced cane toads Bufo marinus throughout large parts of its range, as the toads are likely to cause severe reductions in monitor lizards Varanus spp. and snakes, which are likely to be predators of the species and its eggs and young (J. Woinarski in litt. 2007). Fire regimes are changing across much of its range, with more extensive high-intensity fires, reducing the fine-scale mosaic favoured by this species. This unfavourable change is likely to accelerate with ongoing spread of invasive pasture grasses (Setterfield et al. 2010, 2013). Fire may also magnify impacts due to predation by feral cats, with recent research in the partridge pigeon’s range showing that cats are attracted to burnt areas and have high predation impact in them (McGregor et al. 2015, 2016; Leahy et al. 2015).
Both subspecies are threatened by a change in fire regime to one where fires extend over large areas and the mosaic of fire ages is erased (Fraser 2001; Fraser et al. 2003; Woinarski et al. 2007, Woinarski & Legge 2013). Although early fires burn some nests; extensive, late dry season fires, promote uniform vegetation of tall annual sorghum or invasive pasture grasses, and probably reduce diversity of herbs, forbs and wattles, whose seed comprises part of diet (Woinarski in litt. 2016). Most areas in which the species persists are still under Aboriginal management but traditional fire management that promotes a mosaic of vegetation ages is now much supplanted. Climate change is predicted to cause even more unfavourable fire regimes (J. Woinarski in litt. 2007). Two further threats are associated with fire. Predation by feral cats Felis catus may increase when extensive fires reduce cover (Woinarski 2004, McGregor et al. 2015, 2016; Leahy et al. 2015) and, in the Northern Territory, exotic pasture grasses, particularly Gamba Grass Andropogon gayanus, are invading habitat and change the vegetation structures because the fires they generate are so intense (Rossiter et al. 2003, in Garnett et al. 2011, Setterfield et al. 2010, 2013). Grazing by cattle and other livestock may cause habitat degradation in some areas, and there has been some recent habitat clearance on the Tiwi Islands (ca 30,000 ha) and in the Darwin-Daly area (Woinarski 2004, in Garnett et al. 2011).
Conservation Actions Underway
No targeted conservation measures are known for this species.
Text account compilers
Benstead, P., Dutson, G., Garnett, S., McClellan, R., Symes, A., Taylor, J.
BirdLife International (2021) Species factsheet: Geophaps smithii. Downloaded from http://www.birdlife.org on 21/10/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 21/10/2021.