Thermal imaging Malleefowl mounds – cost effective fauna survey technique

Malleefowl incubate their eggs in a mound of gravel and vegetation where heat is generated from organic decomposition, solar radiation or geothermal sources. Frith (1956) showed that Malleefowl egg incubation was largely achieved by heat generated from decomposition of organic matter and manipulating the covering of soil to keep the temperature within the range suitable for egg development. In most cases, and certainly during late spring and early summer, mounds are opened to release heat. Towards the end of the incubation period (i.e. summer) solar radiation becomes important, as the heat generated from microbial decomposition declines as the litter dries out. Opening and closing the mound enables the Malleefowl to retain a temperature of about 34 oC within the mound for about 9 months of the year. Males have the primary responsibility for managing the mounds, but females are often involved in opening and closing mounds once eggs have been laid. Mound opening and closing normally occurs after sunrise and is completed by about 0900 hrs.

Mound building by the male commences in mid-to-late winter. Between 1-28 (mean 14) eggs are laid between mid-August and mid-February (Firth 1956, Priddel and Wheeler 2005). Eggs are located approximately 50-60 cm below the surface of the mound. Incubation takes about 60 days (Benshemesh 2000). Chicks receive no parental assistance once they have hatched and there is about 80% mortality in the first 10 days of hatching (Priddel 1989).

Malleefowl mounds have a thermal profile that alters significantly when an active mound is opened in the morning. Plates 1 and 2 show an inactive mound and Plates 3 and 4 show an active closed mound. Most of the surface heat generated here is from solar radiation.

Plate 1. Thermal image of an inactive Malleefowl mound in the morning	Plate 2. Photographic image of the mound in Plate 1

Plate 3. Thermal image of an inactive Malleefowl mound in the afternoon	Plate 4. Photographic image of the mound in Plate 3

Benshemesh and Emison (1996) reported on the usefulness of airborne thermal scanners to identify active Malleefowl mounds. Their methodology successfully detected up to 36% of active mounds on cloudy mornings in mid-October and 25% of active mounds in mid-November and about 15% in mid-summer. They suggested that repeated scans would have substantially increased detection rates. They concluded that the methodology was feasible, cost-effective and capable of covering vast areas, although further development was required for broad-scale application. Since then the technology has improved, and may have the potential to record active mounds over a significant area (e.g. mine site, control and adjacent areas).

Newer technology consisting of a tri-camera system that uses an ultraviolet sensitive camera, infrared long wave radiometric camera and a hi-res digital video camera has the potential to improve on the work pioneered by Benshemesh and Emison (1996). We are currently examining the usefulness of this approach to detect active mounds. A helicopter with the three camera system is flown in a grid-search pattern over the search area during the period that mounds are active and open (i.e. early in the morning).

Plate 5 shows the thermal footprint of a Malleefowl mound that was opened early in the morning using the thermal image system mounted in a helicopter.

Plate 5. Thermal image of an active open Malleefowl mound taken from a helicopter

Do you have any experience with thermal image detection of active Malleefowl mounds?

References

Benshemesh, J. 2000. National Recovery Plan for Malleefowl. Department of Environment and Heritage, Canberra.

Benshemesh, J. S. and W. B. Emison. 1996. Surveying breeding densities of Malleefowl using an airborne thermal scanner. Wildlife Research 23:121-141.

Firth, H. J. 1956. Temperature regulation in the nesting mounds of the mallee-fowl, Leipoa ocellata Gould. Wildlife Research 1:79-95.

Priddel, D. 1989. Conservation of rare fauna: the Regent Parrot and the Malleefowl.in J. C. Noble and R. A. Bradstock, editors. Mediterranean Landscapes in Australia: Mallee Ecosystems and Their Management. CSIRO, Melbourne.

Priddel, D. and R. Wheeler. 2005. Fecundity, egg size and the influence of rainfall in an isolated population of malleefowl (Leipoa ocellata). Wildlife Research 32:639-648.