In the pre-dawn darkness on Saturday the 18th of June, twenty-five volunteers and one Park Ranger were greeted with perfectly calm conditions for Tarra-Bulga National Park’s Annual Lyrebird Survey. Overnight showers had passed by leaving moist dripping foliage in their wake.
The survey is designed to monitor the density of Lyrebirds living in 60ha comprising of wet sclerophyll and cool temperate rainforest immediately to the east of the Tarra-Bulga National Park Visitors Centre. There are sixteen monitoring points strategically placed throughout the site and volunteers move to each site before adult male Lyrebirds start their morning calls at dawn. Volunteers then use a compass to record the direction and proximity of the Lyrebird calls. This year we had enough volunteers to cover all but one of the monitoring points.
Following the survey, lines representing the direction of the calls are plotted onto a map, and triangulation is used to establish the spots where birds were calling from. This year the results indicate we had at least nine (male) Lyrebirds calling in our 60ha zone. This corresponds to a density of one adult male Lyrebird per 6.7 ha. You can also assume that there will be female lyrebirds and immature males or non-calling males within our target area. To account for this to get our overall population of Lyrebirds we multiply the number of calling males by a factor of 2.5. It is believed that male Lyrebirds do not begin to breed until they are around 6 or 7 years old.
Summary of Tarra-Bulga National Park Lyrebird Surveys
To all of those people who did the Lyrebird Survey this map can give an indication of what was going on this year.Geographic Information System (GIS) software was used to plot the location of all of the monitoring sites. Then the lines coming out from each site were drawn using the information that all the volunteers recorded during the survey. Once all the lines have been drawn we can then find points where several lines from different monitoring points intersect. At these points we can be confident that there was a Male Lyrebird calling during the survey period.
We were happy to have perfect weather for Lyrebird Counting, still calm conditions meant that Lyrebird calls would be easy to detect. We had an excellent turnout with 32 helpers including a contingent of Scouts. Ranger Craig briefed the early morning crowd about their roles and passed on his knowledge in terms of taking a compass bearing. We then raced out to our monitoring points, in order to be in position before the first birds began calling at the break of dawn. After only a quarter of an hour or so all groups recorded several different birds calling and there were a number of live sightings. It was then (as is the custom) time to migrate to the guesthouse for a hearty breakfast. After all the recordings were logged and mapped we can confirm at least 6 birds were present in the target area, which thankfully shows that the Parks Lyrebird populations are still going strong.