Temporal Patterns of Abundance of Birds Along a Transect in Kings Park, Perth: A long-term study

Abstract

Frequency of occurrence data are available for birds along a transect in Kings Park, Perth, Western Australia from 1928 to 2008. These data show a dynamic avifauna with about a third of the sixty-one bird species recorded declining in frequency since 1928, another third, including new colonisers, increased, while a third showed little or no change. Despite the value of these data, frequency data are a coarse measure of changes in abundance. To provide baseline data on avian abundances for monitoring long-term trends in numbers, monthly counts along the transect were made from February 1996 to October 1999, and August 2001 to February 2002, with additional opportunistic counts from 1986 to 2008. Fifty-five species were recorded between 1986 and 2008. An average of 15 to 20 species were recorded during counts with little seasonal variation. Total species abundances were greatest in winter and spring, and least in summer and autumn. The number of individuals of most species changed seasonally, due in part to variation in detectability, but birds also moved into and out of the park. The numbers of some species differed between years, and there were changes in species composition and abundance following fires that burnt the transect. Between 1986 and 2008 two species, Broad-tailed Acanthiza apicalis and Western Thornbill A. inornata, declined to extinction, with the loss of the Western Thornbill a consequence of the 1989 fire. Other species, including Black-capped Sittella Daphoenositta pileata and Yellow-rumped Thornbill A. chrysorrhoa, are in decline, with local extinction predicted by 2030. The data illustrate the importance of abundance data for long-term monitoring and the importance of Kings Park as a refuge for Perth’s birdlife.