Fire and Birds in a Western Australian Heathland

Abstract

The complexity of avifaunal response to fire is illustrated using long-term demographic data for passerines at Gooseberry Hill, Western Australia, that has experienced an average of one fire every two years in the 41 years since 1957. During a 26 year period from 1972 to 1997, when three major and eight minor fires occurred, the density of Splendid Fairy-wrens Malurus splendens ranged from a high of 105 adults/100 ha in 1985 to 20 adults/100 ha in 1994. Both of these extremes followed periods of similar fire frequency (five fires in preceding 10 years). However, in the ten years before 1985, all fires were of limited extent, whereas the ten year period up to 1994 began with an extensive 100% hot summer burn, closely followed by two smaller reburns. The aftermath of the major fire in 1985 and subsequent minor fires had a major detrimental impact on populations of Splendid Fairy-wrens, Western Thornbills Acanthiza inornata, Scarlet Robins Petroica multicolor and Yellow-rumped Thornbills A. chrysorrhoa, all of which declined during the following eight years, even though the vegetation had nearly recovered to 1985 conditions. This continued decline in bird densities was related to increased mortality of breeding birds and lowered productivity, due to temporary cessation of breeding by Western Thornbills and to increased nest preda-tion and parasitism in Splendid Fairy-wrens. In addition, the broad extent of the 1985 fire reduced opportunities for immigration from elsewhere. Understanding this avifaunal response to fire would not have been possible without an extended period of study. Any fire management plans based on just two or three years data might have yielded recommendations quite detrimental to the fauna they were designed to protect. For the species and habitats studied here, small, patchy burns on a well-spaced rotational basis are to be preferred over regular ‘fuel reduction’ burning of entire habitats, particularly in isolated areas where immigration is unlikely to occur. Once an entire area has been burnt, special care should be taken to prevent a reburn within at least the next 8-10 years.