The breeding biology of the Forest Red-tailed Black Cockatoo Calyptorhynchus banksii naso Gould in south-western Australia. I. Characteristics of nest trees and nest hollows.

Abstract

The Forest Red-tailed Black Cockatoo Calyptorhynchus banksii naso (FRTBC) is a large, iconic forest cockatoo, endemic to the south-west corner of Western Australia. It is currently listed as Vulnerable under the State Western Australian Wildlife Conservation Act and under the Commonwealth Environment Protection and Biodiversity Conservation Act. In this paper, we provide details of nest tree and nest hollow requirements based on details of hollows in 128 nest trees studied over 17 years. FRTBC are monogamous and pairs nest in tree hollows from 6.5–33 m above ground. Most nests are in very large and very old, mature Marri Corymbia calophylla, a long-lived endemic tree species, which is the most important nesting tree throughout the FRTBC range. Nest trees of all species had a mean circumference at breast height of 2.79 m, a mean estimated age of 222 years and a mean overall height of 20.24 m. Marri nest trees had an mean circumference at breast height of 2.76 m, a mean estimated age of 220 years (95% confidence limit 209–231 years) and an average overall height of 20.04 m. The rate of fall or loss of nest trees was high, c. 16.6% per decade. A wide range of hollow types, defined by position of the hollow in the tree, were found. Hollow aspects were also diverse. The mean height to a hollow was 14.49 m. Mean hollow depth was 1.44 m, mean floor space (the longest linear distance across the bottom of the hollow) was 33.2 cm and the mean hollow entrance area was 30 x 34 cm. FRTBC nests are typically, but not always, clustered in the landscape and social interactions within the flock are likely to play a part in the clustering of nests. Nest competitors, including feral European Honey Bee Apis mellifera, Carnaby’s Cockatoo Calyptorhynchus latirostris, Baudin’s Cockatoo C. baudinii and the Regent Parrot Polytelis anthopeplus were recorded using nest hollows once used by FRTBC. In the past Marri was harvested commercially, especially the largest and oldest trees, for timber and woodchips. In recent times the volume of Marri logs has been reduced due to a decline in markets e.g. between 2004 and 2010 a total of 95,436 m³ was harvested (K. Whitford, pers. comm.). Given the importance of large, old trees for FRTBC breeding habitat, conservation of these trees

Climate change indirectly reduces breeding frequency of a mobile species through changes in food availability

“…The FRTBC form monogamous pairs, and after breeding occurs, the juveniles are dependent on the parents for roughly eighteen months to two years after fledging (Johnstone et al. ). Previous studies have shown that breeding occurs across all months of the year with peaks in autumn (April–June) and spring (August–October) and breeding frequency varies significantly between years (Johnstone et al.…”

“…The FRTBC is a highly mobile species, and previous studies have reported that the adults travel long distances (>20 km/d) from their nests in search of food and water, and these movements are changing due to altered water and food availability in SWWA forests (Johnstone et al 2013a). The FRTBC form monogamous pairs, and after breeding occurs, the juveniles are dependent on the parents for roughly eighteen months to two years after fledging (Johnstone et al 2013b). Previous studies have shown that breeding occurs across all months of the year with peaks in autumn (April-June) and spring (August-October) and breeding frequency varies significantly between years (Johnstone et al 2013a).…”

Successional changes in feeding activity by threatened cockatoos in revegetated mine sites

“…Additionally, since suitably sized nesting hollows for black cockatoos generally occur in trees aged 130-200+ years old (Whitford and Williams 2002;Johnstone et al 2013a), the trees at our sites have not yet developed suitable nesting hollows.…”

“…Habitat loss is a major threat to the survival of the three black cockatoos endemic to south-western Australia (the forest red-tailed black cockatoo (Calyptorhynchus banksii naso; FRTBC), Carnaby's cockatoo (Calyptorhynchus latirostris; CBC), and Baudin's cockatoo (Calyptorhynchus baudinii; BBC) (Chapman 2008;Garnett et al 2011;Department of Environment 2012;Johnstone et al 2013aJohnstone et al , 2013b. All three species of cockatoo are listed as threatened under the Commonwealth Environment Protection and Biodiversity Conservation Act 1999, whereas CBC and BBC are classified as Endangered in the IUCN Red List (Birdlife International 2013a.…”

“…All three species of cockatoo forage and nest in the jarrah (Eucalyptus marginata) forest (Johnstone and Kirkby 2008;Johnstone et al 2013a), which is the largest contiguous forest in south-western Australia and is managed for mining, timber harvesting and water catchments, as well as biodiversity conservation (Conservation Commission of Western Australia 2012). Extensive agricultural clearing has reduced the distribution of jarrah from an estimated 5.3 million ha (mapped in Lane Poole 1920) to ~3.3 million ha (Dell and Havel 1989).…”