Carnaby’s black-cockatoo has undergone a rapid decline in the last century, vanishing from a third of its native range between 1970 and 1990 (2) (4). The main reason for this is the clearance of native vegetation for agriculture, which has severely reduced and fragmented this species’ habitat (4) (8). In some cases, parts of south-western Western Australia have lost over 90 percent of their original vegetation, with the remainder being scattered in numerous patches of varying size and quality (12).
In particular, the clearance of heathland and scrubland around its breeding sites has devastated the Carnaby’s black-cockatoo population (2) (4) (8). The adult cockatoos must not travel too far to gather sufficient food to satisfy the high energy demands of the developing nestlings. Where feeding habitat is scattered and fragmented, the adults are forced to forage further afield and for longer, resulting in higher mortality of the young, which may well starve before they can fledge (3) (4) (10). Remaining habitat patches are also being increasingly degraded by weed invasion and by an increase in soil salinity, caused by changing land use practices (2) (4) (8) (13).
The breeding habitat of Carnaby’s black-cockatoo has also been extensively cleared (2) (4) (13). In addition, Carnaby’s black-cockatoo is losing nesting sites as nesting trees are not regenerating, mainly due to grazing by sheep and rabbits (2) (3) (4) (8) (13). Carnaby’s black-cockatoo is also facing increasing competition with other birds and with introduced bees for nest hollows. In particular, species such as the galah (Cacatua roseicapilla) and the western corella (Cacatua pastinator) are invading the range of Carnaby’s black-cockatoo and out-competing it for resources (2) (4) (7) (8) (10).
Although non-native pines provide a reliable food source for Carnaby’s black-cockatoo outside of the breeding season, these pines are now reaching maturity and will eventually be harvested. This could potentially lead to a food shortage for the cockatoos (2) (4) (13).
Carnaby’s black-cockatoo is particularly vulnerable to changes in land use due to the fact it migrates and uses a variety of habitats for breeding and foraging throughout the year (4). Its long-term pair bonds and high fidelity to its traditional nesting sites may also mean that the birds are slow to disperse after habitat disturbances (2).
Carnaby’s black-cockatoo is also susceptible to collisions with vehicles (2) (7) (12) (14), particularly as more habitat is cleared and remaining habitat patches are crossed by roads and railways (2). In addition, its eggs and chicks are often illegally poached due to the species’ popularity and high value in the avicultural trade. Although domestic demand for Carnaby’s black-cockatoo has declined, poaching for illegal export still occurs, and nest hollows are often damaged in the process, making them unsuitable for future nesting (2) (4) (8) (10) (13).
In recent years, severe weather events and outbreaks of disease have caused many fatalities of Carnaby’s black-cockatoos. It is feared that climate change may increase the frequency of extreme weather events such as heat waves and storms, with potentially devastating effects on the already vulnerable cockatoo population (14).