To identify the properties of habitat mosaics produced by fire that enhance the persistence and status of birds in eucalypt-dominated mallee habitats.
Bird surveys were undertaken both at the site and landscape (mosaic) levels. Each of the 28 mosaics was surveyed four times, twice each over the spring/summer periods of 2006/2007 and 2007/2008. These surveys coincide with major breeding periods of birds (a time of higher vocalisations and consequently higher detectability rates) and the arrival of summer migrants.
Two main survey methods were used in each mosaic (see Figure 3), both carried out along a 10 km transect through the mosaic. This was divided into two five-km sections to be completed by two observers (Rick Taylor, Simon Watson). Thus, each mosaic had equal survey effort by each observer.
1) Point counts
Twenty point-count surveys, positioned ~500 m apart along these transects.
- Each point count was of 5 min duration
- Distance from the centre point was measured for individual birds seen or heard, using a laser rangefinder, within the 5 min survey period
- Concurrent recording of all birds was also made within the following categories: (a) seen within 30 m, (b) heard within 30 m, (c) seen outside 30 m, (d) heard outside 30 m
- Rare/secretive species may remain undetected during transect walks and point counts. Therefore, upon completion of the five minute point count, a standardised call playback was used to establish presence of certain target species. Based on pilot survey work, species chosen include Red-lored Whistler (Pachycephala rufogularis), Striated Grasswren (Amytornis striatus), Mallee Emu-wren (Stipitucus Mallee) and Black-eared Miner (Manorina melanotis). These species represent a subset of rare/threatened species that possess one or more of the characteristics: (a) secretive (low calling rates) (b) minimal vocalisations (c) cryptic.
2) 500 m transects
There were 20 transects of ~500 m between point count sites, and these were also used to survey birds.
- Species were recorded as present or absent within several categories: (a) seen within 30 m, (b) heard within 30 m, (c) seen outside 30 m, (d) heard outside 30 m
- Species flying above the canopy during surveys will be recorded separately.
The dependent variables for bird sampling were:
- Bird species richness measured as the presence or absence of species within a fire mosaic. This represents the avifaunal assemblage of that mosaic
- Bird species abundance (index) – measured as the incidence (or reporting rate): the number of 500 m transects in which a species was recorded divided by the total number of 500 m transects surveyed (each 500 m length of transect runs between point count sites)
- Bird species abundance (relative) – number of birds counted within a 30 m radius of each point count (these data were collected in conjunction with distance sampling data; and
- Bird species abundance (density) – density of individual species using distance sampling at point counts.