Data Zone
Justification of Red List category
Systematic monitoring data suggest a population decline approaching 30% is likely to have occurred in the last three generations, a decline that is precautionarily suspected to continue at a similar or faster rate given the ongoing threat of climate change. For these reasons the species is evaluated as Near Threatened.
Population justification
The abundance of Tooth-billed Bowerbirds was calculated from the density and distribution of birds and the area of climatically suitable habitat at different altitudes (Williams et al. 2010a).
Trend justification
There is much uncertainty with the rate of decline in this species. Annual monitoring between 2000 and 2016 (at 1,970 plots at 62 different locations, spanning 0-1,500 m altitude) detected a highly significant rapid decline from 460,000 to 20,000 mature individuals (equivalent to a >95% decline over three generations [25.8 years; Bird et al. 2020]) at both mid- and high-altitude sites. Similarly, reporting rates for 2-ha 20-min surveys declined by 51% from 1999–2018, again with most of the decline in the first ten years (BirdLife Australia 2020). There was also a significant decline in reporting rate of 30%–42% between the first BirdLife Australia Atlas (1977–1981) and the second (1998–2001; Barrett et al. 2002, Garnett et al. 2003). However, many of these reductions are attributable to Cyclones Larry (2006) and Yasi (2011) which severely damaged many court sites, probably killed many birds, and diminished the frequency of calls, and thus detection rates for many years afterwards - declines caused by these events are considered temporary and there were signs of recovery post 2008 in the data. Moreover, there was little change in the reporting rates from 500-m radius area searches from 1999–2018 (BirdLife Australia 2020), no difference between 2000–2007 and 2013–2019 in the proportion of weeks in which the species was recorded (from 33% and 34%) at the School for Field Studies Centre near Danbulla (740–780 m; A. Freeman, M. Craig unpublished, in Williams et al. 2021) and visits within the last five years to almost all known historic locations found none had been vacated. Evaluating all trends over the past three generations, Williams et al. (2021) concluded that the population is suspected to have declined at a rate of 20-29% over the past three generations, principally because of climate change, which is reducing population sizes in a large number of Wet Tropics species (William and de la Fuente 2021). Given the ongoing nature of this threat, the population is suspected to decline at a similar rate in the future, although there are many uncertainties with these estimations.
Tooth-billed Bowerbirds are endemic to the Wet Tropics of north Queensland, Australia from Mount Amos in the north and south to Mount Elliott near Townsville. Their inland limits are the Windsor Tableland and Ravenshoe (Frith and Frith 2004).
Tooth-billed Bowerbirds occur primarily in upland rainforest (Frith and Frith 1984) where groups of male display courts (not leks; Frith 2016) are continually occupied for decades (Frith and Frith 1995). They also display in acacia regrowth (Vinson and Freeman 2006). They attain their highest densities at 800–1200 m altitudes (Williams et al. 2010b), but courts have been found as low as at 423 m (Black Mountain Road, Kuranda; D Chaplin unpublished). They feed on leaves and fruit, with fruit availability affecting court attendance (Freeman and Vinson 2008). They lay 1–2 eggs in coarsely built cup nests, built in high vine tangles (Frith and Frith 2016).
Climate change is the only known threat and could be having both direct effects as a result of increased mortality during heat waves, which have been longer and hotter in the last two decades, and an indirect effect because the dry season has been longer, drier and hotter, which is likely to have reduced resource availability (Williams et al. 2010b, Williams and de la Fuente 2021). Cyclones probably killed many birds and reduced court attendance for many years in some areas (D. Chaplin, A. Freeman unpublished); while their frequency is predicted to decrease, models suggest their intensity will increase (Parker et al. 2018) potentially causing additional declines in the future.
Conservation Actions Underway
Almost entire range within protected areas.
Conservation Actions Proposed
Understand constraints on population size and survival. Identify reasons for sensitivity to climate change and options for countering them. Develop strategies for maintaining remaining populations. Apply adaptation strategies as required.
Text account compilers
Berryman, A., Vine, J., Butchart, S.
Recommended citation
BirdLife International (2024) Species factsheet: Tooth-billed Bowerbird Scenopoeetes dentirostris. Downloaded from
https://datazone.birdlife.org/species/factsheet/tooth-billed-bowerbird-scenopoeetes-dentirostris on 22/11/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 22/11/2024.