Western Australia. Dept. of Environment and Conservation
Place of Publication
Perth, Western Australia
Computing, Health and Sciences
This study examined the behavioural ecology of Carnaby‘s Black-Cockatoo in the Gnangara Sustainability Strategy study area, with a focus on habitat use of pine plantations. The study confirms that the pine is the main food source for Carnaby‘s Black-Cockatoos within the GSS area during the non-breeding season (January-June). The value of the Gnangara-Pinjar-Yanchep pine plantations as a food source for Carnaby‘s Black-Cockatoo should not be underestimated. Large congregations of birds (~3000) utilised the pine plantations for an extended period, mainly January-March but with birds continuing to feeding within the plantations through June. The pine plantations have provided an important and dependable feeding habitat since the 1940s, a period that has seen the abundance of this species decline by at least 50% and its range contract by one-third. The impact of pine removal should also be considered within a suite of broader changes to the GSS landscape. These changes include the loss of feeding habitats off-plantation (e.g. thickets of Banksia sessilis around Neerabup and within the Northwest Corridor) and predictions of declining productivity within areas of Banksia woodland due to reduced rainfall and the spread of dieback, Phytophthora cinnamomi. There is uncertainty about whether the remnant native vegetation in the GSS area will provide an adequate food source following the removal of pine plantations, particularly from January to March when feeding within the plantations is most intensive. This topic requires further investigation. In April and May 2009 (‗dryandra period), at least 4000 birds were concentrated between Neerabup and Boongarra as large aggregations form to feed within thickets of Banksia sessilis. These aggregations probably draw together flocks that through February and March had been feeding: (a) in and around the GSS pine plantations; (b) in the suburban areas to the south and west of the plantations; and (c) in areas to the north of Boongarra. When the dryandra feeding period is completed, the aggregations most likely broke apart again, with birds either returning to feed on pine again or in Banksia woodland areas. This also roughly coincides with the period when breeding birds will begin transitioning back to breeding habitats inland, and from June through August birds may mass into large flocks of several thousand as they shift away from feeding habitats on the Swan Coastal Plain. Large flocks have been observed in July and August around the northern end of the Yanchep plantation, suggesting that birds migrating to breeding sites to the north and east of the GSS area may aggregate in areas of the pine plantations where some food remains and/or the large areas of Banksia woodland. Not all adult birds breed each year, and some birds remain on the Swan Coastal Plain, and between 600-1500 birds are likely to be present within the GSS area during the non-breeding season Food availability in Banksia woodland habitats probably peaks in the late winter-spring period (August-November), since this is the season when the majority of Banksia species on the Swan Coastal Plain are flowering and the fruits of B. attenuata mature. It is unknown how much food remains available in the Banksia woodlands throughout the year, and this topic requires further research. Given the lack of information on the seasonal availability of food for this species, a precautionary conservation step would be the retention of some form of pine. Lower stand densities and larger breaks between stands would encourage greater canopy growth and thus greater production of cones, thereby compensating for an overall decrease in the area covered by pine. If full pine removal is effected, feeding habitat can be restored quickly and at relatively low cost through the seeding and/or planting of native and non-native food species that are well-adapted to growth in a high-disturbance environment. These species include: Banksia sessilis and similar Dryandras, Hakea spp., marri, Erodium, and Pinus spp. However, given the potential negative impacts of introduced species (e.g. Erodium) on other elements of biodiversity, the use of such species as food sources for Carnaby‘s Black-Cockatoo should be avoided. The provision of roosting habitat is a potentially over-looked function of pine, particularly in landscapes where there are few large trees to roost. Thus, restoration objectives for Carnaby‘s cockatoos could possibly be integrated into current strategies to create ecological corridors or be developed as offset measures. The key issues are the need to find suitable roost tree species and to replace feeding habitat that provides food in the January to April period, to compensate for the removal of roost sites and food from pine plantations. Further research is required to identify the potential carrying capacity of the remnant Banksia woodland following the removal of pine plantations. In particular, this research should identify availability of food (and watering points) during January – March.