Researchers use thermal cameras to detect roosting birds
Where do small birds sleep? Mostly in trees is the short answer, but as so often occurs in ecology, there is more to the story…
If you were a bird, a few critical things might influence where you choose to spend the night. First and foremost, you don’t want to be eaten by a predator! And, if you want to get some rest, you can’t rely on alertness, speed and agility to escape owls or tree-dwelling mammals… So, concealment might be important. Second, you want to minimise your exposure to the elements. Smaller bodies burn kilojoules a lot faster than larger bodies, and cold winter nights can take a heavy toll on energy reserves so a thermally buffered location will also be desirable.
“For an activity that takes up a very substantial portion of a bird’s life, and where choices can mean the difference between life and death, we know surprisingly little about the ecology of sleep in birds” said co-author Rohan Clarke.
What little we do know is intriguing – for example within large communal roosts, complicated hierarchies exist where dominant birds take position at the centre of the roost - the warmest and safest position - while subordinate birds must take their chances at the periphery. While it’s relatively simple to investigate these behaviours in species that roost in large groups, it is far more challenging to even detect individuals that roost alone.
In an attempt to overcome this challenge, researchers from Monash University have been using infrared thermography, i.e. a thermal camera/scanner, to locate roosting birds of a wide range of species.
‘Thermal cameras measure heat emission. The difference in signal strength between an animal and the vegetation around it means that we can detect birds in total darkness. Another benefit is that the birds typically remain asleep, which means that this technique creates very little disturbance’, reports William Mitchell, lead author of the study.
To ensure that the technique worked, researchers carried out bird surveys during the day in an Australian woodland, and then repeated the same surveys at night using a thermal camera. They then compared detection rates of the two methods. 21 of 22 species that were commonly detected during day surveys were also found roosting at night.
“To date, we’ve recorded simple traits such as height and visibility of roost sites but this method really opens the door to dig deeper into the nocturnal behaviour of diurnal birds’ said Rohan Clarke.
“While there are some limitations, it’s great to get proof of concept for this method. We were able to quickly and efficiently detect roosting individuals for most species in our bird community with minimal disturbance” concludes William Mitchell
This research was recently published in The Journal of Field Ornithology:
Mitchell, W. F., and Clarke., R. H., 2019. Using infrared thermography to detect night-roosting birds. Journal of Field Ornithology. https://doi.org/10.1111/jofo.12285.
The charismatic Mallee Emu-wren, once widespread in the Murray-Mallee region of South Australia and Victoria, has in recent decades, been restricted to a small network of Victorian reserves by a series of bushfires.
Mallee Emu-wrens are specialised to live in hummock-grass vegetation, and while this key habitat eventually regenerates following fire, Mallee Emu-wrens have no capacity to recolonise such areas.
Another large-scale bushfire could push the endangered Mallee Emu-wren past the point of no return.
They have just recently been involved with the successful translocation of an additional 38 birds back into Ngarkat Conservation Park in South Australia.
“In 2018, 78 Mallee Emu-wrens were translocated from Murray-Sunset and Hattah-Kulkyne National Parks in Victoria to Ngarkat Conservation Park as part of a trial to determine the suitability and effectiveness of translocation as a conservation strategy for the Mallee Emu-wren,” said Dr Rohan Clarke.
“Using this translocation as a model system, we are looking at which planning, implementation, and long-term monitoring can be improved in translocations of threatened species,” he said.
PhD candidate Will Mitchell said tracking of the released birds was difficult given their tiny size and elusive behaviour.
“We were blown away when we found a significant number of paired birds with young fledglings,” he said.
Will hopes that a key outcome of his research will be to provide a framework for conservation managers to assess how many individuals can be removed sustainably from a population for the purpose of translocation.
“At a local scale, the successful re-introduction of the Mallee Emu-wren to Ngarkat Conservation Park will increase the global population of the species, provide an insurance population against further catastrophic wildfires in currently occupied Mallee Emu-wren habitat, and pave the way for larger-scale re-introductions into other reserves from which the Mallee Emu-wren has become extinct,” Will said.
Co-authored by Rohan Clarke
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02/20/2019 in NewsResearchers use thermal cameras to detect roosting birds Where do small birds sleep? Mostly in...
11/30/2018 in NewsThe charismatic Mallee Emu-wren, once widespread in the Murray-Mallee region of South Australia...
- Matcott, J., Baylis, S. & Clarke, R.H. (2019) The Influence of Petroleum Oil Films on the Feather Structure of Tropical and Temperate Seabird Species. Marine Pollution Bulletin.
- Baker, D.J., Garnett, S.T., O’Connor, J., Ehmke, G., Clarke, R.H., Woinarski, J.C.Z. & McGeoch, M.A. (2018) Conserving the abundance of non-threatened species. Conservation Biology.
- Baylis, S.M., Drynan, D., Clarke, N., Van, M., Sunnucks, P., and Clarke, R.H. (2018) Estimates of wear rates in metal bird bands, with applications for survival and movement models of marked individuals. Journal of Field Ornithology.