Lyrebirds and their relatives are overlooked major dispersers of mycorrhizal fungi.
LINKED PAPER
Superb Lyrebird Menura novaehollandiae mycophagy, truffles, and soil disturbance.
Elliott, Todd F. & Vernes, Karl. 2018. IBIS. VIEW
Superb Lyrebirds (Menura novaehollandiae) are symbolic of Australia and are found through a range of habitats from southeastern Queensland to Tasmania. These ground foraging birds are one of the ultimate mimics of the bird world, sometimes perfectly copying more than a dozen unique sounds ranging from other bird species’ calls to chainsaws.
In our recent IBIS paper, we show for the first time that Superb Lyrebirds eat a diversity of fungi (at least 14 species) and may be providing a vital ecosystem function through the dispersal of mushrooms that are essential to the health of Antarctic beech and Eucalyptus forests in southeastern Australia.
Figure 1. A diversity of sequestrate fungi (truffles). Associations formed by these and related fungi are important for plant health and as foods for a diversity of birds, mammals, and invertebrates around the world.
Fungi form a wide variety of associations in the environment. The majority of vascular plants depend on mycorrhizal associations with fungi for their nutrient uptake. Most plant roots are relatively inefficient at nutrient absorption on their own and rely heavily on the underground thread-like networks (mycelia) of fungi to “infect” them and increase their nutrient absorptive abilities. The plant gives the fungus sugars produced by photosynthesis in exchange for water and minerals that the fungus extracts from the soil. These associations are vital to the success of most plants and many fungi.
Many of the fungi that form these associations have truffle-like (sequestrate) fruiting bodies. These truffles fruit below ground, making it difficult for them to disperse spores and for associated plant roots to become colonized by the symbiotic fungi. These fruiting bodies are highly nutritious to animals, and it has been widely suggested that mammals and insects are their primary dispersers. In this study, we apply methods not previously used in bird studies to detect fungal presence in diets and report for the first time that superb lyrebirds eat truffles and other fungi. We suggest that birds may be an overlooked and vital disperser of mycorrhizal fungi.
Figure 2. Fungi eaten by Superb Lyrebirds in New England National Park, Australia (a) Brown bolitoid spore with longitudinal ridges extracted from the scats of Superb Lyrebirds that were similar to those found in Rossbeevera vittatispora. (b) Fruiting bodies of R. vittatispora collected in study area. (c) Spore reminiscent of a species of Descolea found in the scats of Superb Lyrebirds. (d) A sequestrate Descolea species collected at study site. (e) Spore reminiscent of members of the Russulaceae found in the scats of Superb Lyrebirds. (f) A cluster of spores reminiscent of the genus Hysterangium found in the scat of Superb Lyrebirds. (g) Unidentified spore with prominent apiculus found in the scat of Superb Lyrebirds. (h) Unidentified fusoid spore; possibly an Ascomycete found in Superb Lyrebird scats.
Fungi have been vastly underreported in the diets of birds, and we believe this may be due to methodological flaws in historic bird dietary studies. Most fungal spores are under 30 microns (1 micron is 1,000th of a millimeter) and are thus difficult to detect at less than 400X magnification. Most bird studies do not examine diet samples at sufficiently high enough magnification to determine whether or not spores are present. It is difficult or impossible to macroscopically recognize fungi in crops or stomach samples, as fungal tissue is very soft and breaks down quickly.
Most mammals that eat fungi have seldom (or never) actually been observed feeding on fungi; reports of this dietary component are generally based on microscopic examination of fecal samples. However, the majority of reports of fungi consumption by birds are based solely on chance feeding observations. As we demonstrate in this study, we think this human sampling error has led to a bias in the understanding of many bird diets. The bias may also be impacting hypotheses of fungal biogeography, since some migratory birds have the potential for much wider spore dispersal than mammals or insects.
Many of the Australian mammals that were historically key dispersers of symbiotic fungi are endangered or virtually extinct, so birds may be one of the last remaining groups of organisms dispersing these vital organisms across the landscape. We urge other researchers working on bird diets to adopt methods similar to those we outline in this study and determine how widespread this phenomenon is in bird communities around the world. There are endless ecological, nutritional, and dispersal research questions to be asked about these associations, and some of the answers may prove birds’ associations with fungi to be vital to the health of forest systems around the world.
Image credit
Featured image: Superb Lyrebird foraging for fungi. © Todd F. Elliott
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