Counting cassowaries: what does cassowary sign reveal about their abundance?

摘要

The use of surveys of sign (e.g. dung, tracks and sightings) to estimate abundance is a method in common usage with a variety of vertebrates, especially forest species and those with cryptic habits. Particularly for endangered species, such as the southern cassowary, Casuarius casuarius, the resulting abundance estimates, at both regional and local scales, can be fundamental to management and conservation decisions. Current estimates of regional cassowary abundance in North Queensland are based on the results of surveys that documented indicators of cassowary activity across the Wet Tropics Region. When applied to population abundance estimation this approach assumes (i) that cassowary sign is as likely to be encountered on trails as it is in the forest generally, and (ii) that there is a relationship between the amount of cassowary sign encountered and the number of birds using a trail. These assumptions were tested in a project conducted in Wooroonooran National Park, north Queensland. In failing to support either assumption, the fieldwork identified the need for the improvement of large-scale survey techniques for cassowaries, and for caution in the application of this method and the interpretation of its results more generally. In the case of cassowaries, improvements to the current method could be achieved by incorporating multiple surveys at each site, assessment of local use of trails by cassowaries and of fruit abundance at the time of surveying.