6. Tidbinbilla studies

Tidbinbilla Lyrebirds

Start of the Camel Back trail at the bottom of our study area
View south in July 2008

July has been a busy month for the 'Lyrebird Team' at Tidbinbilla. Chris Davey, Ed Slater and I have been mulling over how we should best continue with the studies we have been carrying out at the Tidbinbilla Nature Reserve and we have decided it is now time to revise some of our methods and move to other ways of monitoring the Tidbinbilla Superb Lyrebird populations. In particular we have been thinking about better ways to account for the number of lyrebirds on our main study plot.We do not have the time nor the energy to search each spring for all the active nests but we ought to be able to account for the number of singing and territory holding males present in the breeding season. Our automatic sound recording station can no longer provide the necessary data for this purpose but it has fulfilled its role splendidly as an early detection system during the first few years of the re-establishment of the lyrebird population. Multiple stations might solve the problem but that idea is not practicable with our limited resources and time. We need to keep it very simple but robust.

Superb Lyrebirds are spectacular songsters! Their song output is all high energy stuff and is commonly sustained for long bouts of singing, particularly at dawn but again at dusk. In their song they mix distinctive lyrebird elements, including regionally characteristic territorial calls, along with huge amounts of mimicry. They sing in the depths of winter and they sing from within dense mountain forests where the reverberation of sound is magnificent! There are few other birds calling at this time of the year. Listening to lyrebirds is a truly unforgettable experience.

Click the following to hear a short segment of Superb Lyrebird song:

TNR%20hut%20sample.mp3

This recording was made in territory 6 (see later) early in the morning on 29th July this year.

By way of introduction it is probably necessary to mention a few other important features of lyrebirds. First, there are two species. A northern Albert's Lyrebird Menura alberti which is restricted in range to a relatively small area of mountain forests in South-eastern Queensland and far north-eastern NSW. The second species, the Superb Lyrebird Menura novaehollandiae, has a much larger distribution in south-eastern Australia extending within the Great Dividing Ranges and associated coastal wet forests from northern NSW to Melbourne. Superb Lyrebirds have been introduced successfully to Tasmania. This occurred in the 1930s but they are still restricted to the few areas near where they were originally liberated in the south of the island. In Canberra we are near to the western limits of the range of the Superb Lyrebird but, nevertheless, they are widespread in the ranges to the west of the city, at least they were until the disastrous fires of early 2003! It is also important to remember that lyrebirds breed in winter. Females lay a single egg and perform all of the incubation and chick rearing duties. Males indulge in long periods of singing, mostly, in the case of Superb Lyrebirds, from specially prepared stages or courts or mound courts. Again in the case of Superb lyrebirds these are cleared, roughly circular patches of raked soil on the forest floor that are constructed by the male and are kept clear during periods of use. This sort of breeding strategy is often termed lekking and the system of courts spread across a territory, as used by Superb Lyrebirds, has been termed a dispersed lek (see Paul A. Johnsgard 1994 Arena Birds, Smithsonian Inst. Press).

Landsat images of the ACT from before the fire (left) and on the 26th January 2003 (right) when the fire was still burning to the south in the Namadgi National Park (plumes of smoke visible drifting SE). Our study site at Tidbinbilla is marked by the blue arrow on the left-hand image. The white lines indicate the ACT borders with NSW and shows that most of the western half of the Territory was destroyed by this fire


Superb Lyrebird display mound or court - July 2008

Now back to our studies!

We have been trying to follow the recovery of the population of Superb Lyrebirds in the forests surrounding the Tidbinbilla valley following the wildfire that burnt out the whole area in January 2003. In part we have done this by annual one day co-ordinated surveys along all the regular trails within the Nature Reserve. These one-day surveys have been organized each winter since 2004 and have depended on the help of a bunch of enthusiastic volunteers from the Canberra Ornithologists Group. The method certainly gives us an overall idea of distribution and with it some idea of the relative densities of lyrebirds across the valley but to look at population recovery in more detail we decided to concentrate our efforts within an area that had been studied in great detail nearly 50 years ago.

A diagrammatic representation of the Superb Lyrebird territories found in the Tidbinbilla Nature Reserve during each of the three winter surveys of 2004 (red), 2005 (blue) and 2006 (yellow). The main ridge lines are indicated in brown and the walking trails used for surveying the whole valley are shown in green

Norman Robinson at the weather station near the CSIRO hut on the study site in the 1960s
Our automatic recording station was set up near this point.

Another view of the Tidbinbilla hut. This site was referred to by Norman Robinson as the High Camp. Note the microphone cables running off into the study area. This array of microphones was used to sample the song output from lyrebirds occupying several surrounding territories. Associated cables also lead to thermistors that were used to record air temperature close to selected display mounds in the same territories

Norman Robinson at a Superb Lyrebird's display mound - October 1964

Jim Bell and Charlie Kogon with piles of microphone wire during a clean up at the hut site in September 1967

In the early 1960s Harry Frith and Norman Robinson carried out innovative studies on Superb Lyrebirds at Tidbinbilla. Norman, in particular, developed an interest in the mimicry content of lyrebird song and by applying new techniques of field recording coupled with the newly emerging technologies of bio-acoustics he made significant advances in the understanding of Tidbinbilla Superb lyrebird song structure and particularly the role of mimicry. A newly aquired Kay-elemetrics Sonagraph permitted the spectral analysis of sound samples. Being able to graphically view the frequency and amplitude structure of sound was crucial in characterizing song. This had not been possible before. It was cutting-edge science at that time. Norman worked for CSIRO and with Harry Frith, who was the Chief of the Division of Wildlife Research they established what at the time was a world class wildlife sound laboratory equipped with one of the very first Sonagraph machines. This laboratory was the starting point for the extensive archive of regional wildlife sound recordings that has been inherited by the Australian National Wildlife Collection. With this background it is by far the largest and most comprehensive collection of Australian wildlife sound recordings and, of course, includes an enormous collection of lyrebird material!

Vertical aerial photo-image of the study area at Tidbinbilla taken shortly after the wildfire in January 2003. The main creek lines are highlighted in blue. The Camel Back fire trail is also clearly visible

Again, returning to the Tidbinbilla of today it is important to realize that our present studies have developed from these important earlier investigations. Using information from the CSIRO studies (Robinson and Frith 1981 Emu 81:145-157) and Norman Robinson's preserved field notes (now in the ANWC sound library) we have been able to delineate their original study area above Mountain Creek with some confidence and with this as the starting point we have tried to follow the re-occupation by territory holding males within this particular area. Our aim has been to see how long it takes for numbers to return to those observed years ago by Norman Robinson and Harry Frith.

The creek system in the study area. The altitude difference between the upper and lower sides of this image is a fall of more than 200m. The dots indicate the positions of nests found during the study by Robinson and Frith in the early 1960s

A view in the area where the CSIRO hut had once stood. Remains of the galvanized water tank can be seen. This picture was taken on 8th May 2003 four months after the wildfire. The hut and most of the other associated materials had been removed from the site many years before the fire

The old hut site on 8th May 2003 - four months after the fire. The remnant base-plate for the weather station (see picture above from the 1960s) is visible in the left foreground

Panorama at the hut site (Norman Robinson's High Camp) taken a year after the fire (January 2004). The slow regrowth of ground cover or dense shrub layer is evident

Unfortunately, we were unable to gain access for several months after the devastating wildfire of January 2003 because of the danger of falling burnt timber but eventually we were given permission to make short visits. Initially, the lyrebirds occurring on the study area were easy to detect. This was especially so during the first year because during that time there was almost no ground cover. It was abundantly obvious that few birds were present. Signs of lyrebird activity were found immediately we inspected the study area. Our first question was - where did these surviving lyrebirds come from? Did they survive as residents within the area or were they immigrants from some more distant refugia? We have no idea. Because the wildfire was so widespread and so intense it is difficult to see how they could have survived much better elsewhere. We may never know the answer to this critical question but we have some clues in that the song structure does not seem to have altered very markedly when compared with the recorded songs of earlier years. This suggests that the cultural characteristics have been maintained. For example, the highly distinctive whip-crack call of the Eastern Whipbird Psophodes olivaceus is not included in the list of mimicry we can recognize today nor was it in the past. This is unusual in that Superb Lyrebirds elsewhere throughout their wide range frequently include Eastern Whipbird mimicry but not at Tidbinbilla! There are no Eastern Whipbirds in the Tidbinbilla Valley catchment.

A view into the weather-proof box containing the automatic sound recording equipment used at Tidbinbilla


The gear in the box in July 2008
Some technology improvements and some compromises!

Our microphone in position.
A Sennheiser K6 power-unit with ME62 omni-directional capsule under a Rycote Softie. The AA battery can be expected to perform reliably and continuously for at least 8 days. Photo taken July 2008

Back to our survey methods. We set up an automatic sound recording station which we then ran for a week each month for the next five years. These 50 or so week-long samples form the basis of our observations on the return of lyrebirds to the study area. Each sample contains a series of 10-second long sound clips taken at half hourly intervals night and day for the whole week. This gives us 48 acoustic samples per day. The analysis of these data is still in progress but it has certainly provided us with a good measure of the intensity of lyrebird calling month by month through this period of five years.

Calling frequency of Superb Lyrebirds at Tidbinbilla, month by month, for three winters.
Blue columns indicate the same winter periods.
Sampling did not occur from November 03 until April 04 nor from November 04 till April 05.

Calling frequency of Superb Lyrebirds at Tidbinbilla according to time of day.
Data from August - October periods shown in blue above.

In addition, we have done ground searches across the area to detect lyrebirds. In the early days this was relatively easy and we considered it a reliable method of finding where lyrebirds were active and indeed most times we were pretty sure that all birds were seen. As the vegetation thickened it became increasingly difficult to move about the study area and to see lyrebirds or even find the evidence of their scratchings in the soil which would confirm that they were foraging in particular areas. Ground cover became very dense and this method was clearly becoming impracticable.

We thought about plotting the distribution of display mounds. We tried a transect surveys method to plot sample segments of the area but this proved to be too time consuming and in any event was considered it to be inadequate for determining the number of birds in any reliable way.

The transect trail (2km of the Camel Back Trail) along which we counted singing Superb Lyrebirds in July 2008. Change in elevation from bottom to top was approximately 900m to 1000m ASL.

In July 2008 we decided to do some count surveys along the main trail that leads up through the centre of the study area. We planned to start at dawn and run the trail up and back two or three times. By taking GPS (Global Positioning System) fixes each time we heard a calling lyrebird and by noting the compass bearing to each singing bird from two or more Waypoints we would plot the positions of each singing individual. Numbers of birds detected each transect fell off remarkably quickly after the first two hours following first light and we concluded that it was unrewarding to do more than a single run up and back down the trail. The climb involved a 200 metre difference in altitude so the less often it had to be done the better! We did four consecutive morning counts with two ascents and two descents each morning, thus giving four transect counts per day. The results were spectacularly convincing that we could detect practically all birds in a single run up and down! The following map shows what we concluded to be the distribution of singing males in July 2008.

Waypoints used on the first ascent transect 20th July 2008. Note that waypoint 1 is missing on this map but was at the start point

Plotted positions of singing Superb Lyrebirds across the study site at Tidbinbilla in July 2008. Colours signify plots from different transect runs and different days

Deduced Superb Lyrebird territories constructed from field data (above) collected 19th -22nd July 2008. The size and shape of these territories is arbitrary and does not necessarily represent the true area for any one of them. These representations are purely to indicate the distribution of discrete male territories. Numbering is also arbitrary

To finish here are three more cuts of Tidbinbilla Superb Lyrebird song. This is the male from territory 9 (on the map above) singing at a little after 0800hr on 29th July this year. The three cuts follow in sequence and are continuous but the original was slightly edited.

These recordings, by the way, and the one earlier, were made on a minidisc (Sony Recording MD Walkman MZ-R900) as compressed files, expanded to AIFF files, edited in Peak 4 and then re-compressed to MP3 format using Amadeus ll so they could be added to this blog. Not much loss of detail despite such treatment!

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Roll on 2009 and our next Tidbinbilla lyrebird surveys!

Frozen trail-side pool - 24 July 2008