Contact Call | Volume 10 Number 2 | June 2021
Most of you, who photograph birds at nest would be familiar with the way birds use lichens in the construction of their nests. While very decorative, the lichens probably play an important role in camouflaging the nest. Lichens are of course part fungi, part algae.
However, fungi may be used in other ways by bird nest builders. Some fungi produce aggregates of fungal threads called rhizomorphs, made up of individual hyphae, bound together and coated in a tough melanized substance, water-repellent and resistant to dehydration. These may be as fine as hair or quite coarse. Rhizomorphs have been found in the nests of many bird species and may be used as (1) lining material (2) structural material, or (3) attachment and anchoring of nests to the substrate.
Spectacled monarch nest with rhizomorphs. Image: Frances Guard.
Twenty-five different species of fungi, mostly in the Marasmius group, (pin wheels or horse hair fungi) have been identified, to date, in bird nest construction (these were all overseas.)
Some were used almost exclusively as lining material in the nests. This living material may produce volatile chemicals. It is hypothesized that they could play a role in controlling parasites in the nest and on nestlings.
Others were used as attachments and anchors and six of these were “litter trappers”, which are normally very strong as they carry heavy loads of leaf litter. “Litter trappers” are fungi that decompose dead leaves by forming aerial tangles of rhizomorphs which capture leaves before they fall to the ground where there is fierce competition with other fungi decomposing the litter. This suggests that birds may preferentially select rhizomorphs adapted to bearing heavy loads, for nest attachment. Still others were woven into the body of the nest.
Unknown nest with rhizomorph lining. Image: Frances Guard.
After learning about this, I started to look out for bird nests in Queensland. I found one that was, I think, built by a Spectacled Monarch. In its walls were hair-like black rhizomorphs. Other materials in the nest were mosses, spider webs, fern frond skeletons and strands of other plant material. All these others occur much more commonly in the area than fungal rhizomorphs. Why and how did this little bird find and select these fungal threads, when other materials are much more common and accessible? One Yellow-throated Scrub-wren nest was full of rhizomorphs, curiously bound with leafy liverworts. Many questions are raised by these findings.
Firstly, how many more birds in Australia use rhizomorphs? Secondly, is it just a random occurrence? Birdwatchers can help answer this by looking out for abandoned nests and identifying the materials used, and noting whether they include fungal rhizomorphs. Thirdly, which of the many rhizomorph-producing fungi are used in bird nests? It may be that I can identify the fungal species by extracting DNA from the threads. This will give us a greater idea of the diversity and potential need for conservation of these important litter recycling fungi in our forests.
You can help!
I am looking for help identifying the presence and identity of fungal rhizomorphs in Australian birds nests. But its essential that we don’t disturb any nesting birds. Please do not go near or disturb birds nests that are being used or may be reused. Only approach a nest if it has been completely abandoned.
If you find an abandoned nest with rhizomorphs present, please photograph it, and either notify me, or carefully make collections of the rhizomorphs, which can then be analysed for DNA.
My contact details are 0477 621 548 and email email@example.com
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