Wader numbers and distribution on Eighty Mile Beach, north-west Australia: baseline counts for the period 1981-2003

This paper analyses ground counts and aerial surveys of high-tide wader roosts conducted over the 23-year period from 1981 to 2003, at Eighty Mile Beach, north-west Australia. It provides a baseline data set with which later count data can be compared. Over the study period, Eighty Mile Beach held a maximum of around 470,000 waders in any given year. This represented around 20% of the total number of migratory waders visiting Australia each year and around 6% of the total East Asian – Australasian Flyway migratory wader population. The most numerous species were great knot (169,000), bar-tailed godwit (110,000), greater sand plover (65,000) and oriental plover (58,000). Distribution of waders along the beach was not uniform, with up to 85% occurring in the section between 25 km and 80 km south of Cape Missiessy where, at peak, numbers averaged 7000 per kilometre of shore; however, distributions for some species diverged from this pattern. Count data showed that waders arrived in north-west Australia over an extended period from July to October. The majority of these birds remained at Eighty Mile Beach throughout the nonbreeding season (austral summer) although some smaller waders used Eighty Mile Beach as a staging point. Most adult birds left on northward migration in March–April of the following year. The number of (mainly) immature birds remaining at Eighty Mile Beach over the May–July period was equivalent to 9% of the peak spring/summer population. The counts also showed that Eighty Mile Beach, especially the southern half, is important for resident wader species. Threats to its ecological integrity are identified and the introduction of enhanced long-term protection measures recommended to ensure that key sections of Eighty Mile Beach are managed for the benefit of the internationally significant numbers of waders occurring there.