1. Tidbinbilla studies

A long-term study on the effect of bushfires on Superb Lyrebirds

Some background details based on a submission to Environment ACT for permission to work on lyrebirds at Tidbinbilla

The avifauna of Australia includes many unique species. One of these, the Superb Lyrebird Menura novaehollandiae, has become an iconic species and no more so than at Tidbinbilla Nature Reserve, ACT. Much of the pioneering research on the vocalizations and behaviour of the Superb Lyrebird was conducted in what is now the Nature Reserve at Tidbinbilla (Robinson & Frith 1981; Robinson and Curtis 1996; Higgins et al. 2001).

Tidbinbilla Nature Reserve has become well known for its Superb Lyrebirds. However, a catastrophic wildfire that occurred in the Brindabella Ranges west of Canberra in January 2003 burned a very large area including the whole of the Reserve. The effects of this devastating January 18th bushfires on the Tidbinbilla lyrebird population were therefore, and not unexpectedly, of considerable concern.

It seemed appropriate after the fire in 2003 to see what had happened to the lyrebirds of Tidbinbilla. Importantly, we were able to locate the exact area of creek system used during the earlier studies by Robinson & Frith (1981) and an investigation of this area in May 2003 was disturbing. It was clear that the intensive heat of the fires had greatly affected the microfauna of the soil and had completely destroyed the leaf litter, both elements critical to the rate of re-establishment of ground flora and consequently the continued survival of any ground-feeding avifauna. Superb Lyrebird abundance was therefore regarded, at that time, as a primary indication of habitat recovery within the Tidbinbilla Nature Reserve and an appropriate study began.

Populations of Superb Lyrebird are known to recover remarkably well following wildfires even of the most severe type (Smith 1988). Our superficial look over the study area near Mountain Creek in May 2003 confirmed, as expected, a complete lack of Lyrebird display mounds and no indications of any Lyrebird vocalizations despite this being the time of year when song output should normally be at its most intense. It was, however, only 4 months after the fire and it seemed reasonable to suppose that breeding would not occur during this first post-fire winter. However, signs of Lyrebirds feeding activity were found, although no birds were seen. We concluded that lyrebirds were certainly present but obviously in greatly reduced numbers and not singing.

In the years since 2003 our aim has been to obtain measures of Superb Lyrebird distribution and abundance over time in order to follow the recovery of the population in the Tidbinbilla Nature Reserve. Because of the widespread nature of the fire and the sedentary nature of lyrebirds it was expected that any population recovery would come from individuals that survived within the area or from nearby areas, but we really have no way to confirm this supposition.

A relative index of population numbers was initially obtained by measuring vocalisation frequency. Robinson & Frith (1981) had reported a mean territory size at this Tidbinbilla study site of 2.4 ha and a density of mounds of 17/ha (6-38) giving an average of 42 mounds for each territory (20-83). Counting active Lyrebird display mounds might therefore have provided a measure of distribution and relative density (Smith 1988, Higgins et al. 2001) but we concluded that it was too time consuming and impractical for our purposes once the shrub layer vegetation became dense across most of the area.

Transect counts of calling birds in mid winter and territory mapping of singing birds at the height of the breeding season song period have proved to be more effective ways to provide measures of distribution and numbers. Using these baseline data we have tried to assess, on a year to year basis, the distribution and status of Superb Lyrebirds at Tidbinbilla Nature Reserve.

References

Higgins, P.J., J.M. Peter & W.K. Steele (Eds) 2001. Handbook of Australian, New Zealand and Antarctic Birds. Volume 5: Tyrant-flycatchers to chats. Oxford University Press: Melbourne.

Robinson, F.N., & H.S. Curtis 1996. The vocal displays of the lyrebirds (Menuridae) Emu 96: 258-275.

Robinson, F.N., & H.J. Frith 1981. The superb lyrebird Menura novaehollandiae in Tidbinbilla (ACT) Emu 81: 145-57.

Smith, L.H. 1988. The life of the lyrebird. William Heinemann, Australia: Melbourne.

A reminder. Aerial views before and immediately after the 2003 bushfire west of Canberra.
The study area is indicated by the arrow