Contact Call | Volume 11 Number 1 | March 2022
Birds and fungi have close associations. Birds and all other animals on earth, including us, are dependent on fungi for our existence. All our fruits and vegetables depend on fungi; all our livestock survive only because of fungi; fish require fungi; all natural fibres such as cotton, bamboo and wool require fungi, and indirectly, all our coal, oil and natural gas came into existence because of fungi.
Fungi are largely out of sight and out of mind, and it is only in the last 100 years or so that their vital role on Earth has been recognised. Overall, schools and universities still teach very little about fungi, except for those of economic importance (eg, yeasts) or medicinal value (eg, penicillin and statins).
Firstly: an introduction. There are millions of fungal species. The fungus itself may be a single cell, or threads of cells called hyphae (hyphal threads), or a collection of them called a mycelium. These cells and hyphae live in soil, wood, on and inside us, and just about everywhere else, but it is often only when they fruit we become aware of their presence.
Their fruit may be minute, such as the black fuzz that grows in shower recess grout, or that green fuzz on a long forgotten plum in the fridge (collectively called moulds or microfungi: micro = small), to huge fruit bodies weighing half a tonne or more (collectively called macrofungi: macro = large). In USA’s eastern Oregon’s Blue Mountains there is a fungus mycelium that covers 7.8 square kilometres, and may be over 8,000 years old.
Amongst the microfungi, some are single-celled parasites of animals. One group produces minute spores that can swim: some of these, the Chytrid fungi, are infecting and killing our frogs with what is called Chytrid disease. Another group of microfungi lives only in the digestive tract of animals, including us.
Many live in a symbiotic relationship with plants, as cells within the tissues of leaves, flowers, fruits, seeds and roots. These are collectively called endophytes (endo = inside, phytus = leaf). One of these specialist groups, called ectomycorrhizae (ecto = outside, myco = fungus, rhiza = root) are essential in the growth and survival of all trees, shrubs, grasses and other plants, and attach themselves to the outside of plant roots. Here they pass water and nutrients, especially phosphorous and trace elements, to the plant. The plant “pays” for these by supplying the fungi with sugar that it makes using sunlight and photosynthesis. The plant and fungus “communicate”: if the fungus is not getting enough sugar it cuts back on the nutrient supply and the plant “recognises” this and increases sugar output to the fungus. Conversely, if the plant needs more water or trace elements, it may cut back on the sugar supply to the fungus, encouraging fungal output.
Some are brightly coloured or of bizarre photogenic shapes, and some disperse their spores by attracting insects (eg, blowflies) using foul odours, fruity perfumes (eg, butterflies and moths), or earthy odours, ie the truffles that spread their spores by being eaten by birds and small marsupials.
Some of these macrofungi are also symbiotic with plants and live inside plant roots, growing small fungal masses inside the plant’s cells. They do the same job as the ectomycorrhizae but are called endomycorrhizae (endo = inside).
By far the most conspicuous of the macrofungi are the decomposer / recyclers. These grow on any carbon-based material such as living and dead trees, stumps and branches, decaying leaves and bark, animal manure, and even dead fungi. They break complex carbon compounds such as cellulose, lignin, fats and sugars into simpler molecules that plants can use. Without the recyclers we would be neck deep in dead plant and animal debris in no time.
Now, with that background, we can get onto bird and fungus associations.
Firstly, birds eat fungi as food. Surprisingly, despite the myriad bird watchers out there, very few accurately record what birds are feeding on. Terms like “seeds and fruit” appear in literature, but useful comments such as Red-tailed Black-Cockatoo eating Beach Almond seeds, seem to fall through the cracks. Some comprehensive literature mentions fungi amongst foods consumed, but there is little documentation.
Personally, I have observed fungi being consumed by Emu, Cassowary, Malleefowl, Brush-turkey and Orange-footed Scrubfowl. In literature, Lyrebirds and Eastern Yellow Robin have been recorded eating fungi.
Many of these avian-preferred fungi are in a collection of species called truffles. Truffles are small, globular fungi that grow just beneath the soil surface, where they are invisible, but produce odours which animals can smell. The animals dig the truffles out. In fact, truffles are distributed almost solely by animals. The truffle is consumed, the animals travel some distance and the spores, unharmed, are pooped out in new places. All truffles are endomycorrhizal, so their distribution close to potential host plants is vital for the health of the bushland.
I have also observed Mycena (small mushrooms that grow on wood or soil) being eaten by Brush-turkey and Eastern Yellow Robin. Orange-footed Scrubfowl have been seen pecking bits off Crepidotus (a small bracket-like gilled fungus that grows on dead wood or bark of trees), and Agaricus austrovinaceus (a quite large mushroom). Filoboletus manipularis (small grey mushrooms that grow in clusters on wood) are consumed enthusiastically by Brush-turkey, as is Pluteus petasatus (a widespread large pale mushroom that grows on mulch).
Sometimes in the rainforest one finds a trail that is obviously used extensively by Brush-turkey and/or Orange-footed Scrubfowl. It is always worth a search along these trails after heavy rain because a wealth of mushrooms and other fungi spring up along the trail. Some spores are probably carried on the feet, legs and in the feathers, but many are probably transported in the birds’ droppings.
On the subject of Brush-turkeys and Orange-footed Scubfowl, both build large nests of leaves and litter and, once abandoned, these are often great places to find small colourful fungi. They may grow in large numbers on the decomposing leaves and, would, over time, reduce the mounds to compost which is distributed by other animals, wind and rain.
Some birds use fungi as decoration or to assist in camouflage of their bowers or nests. Satin Bowerbird and one of the Lyrebirds, for example, are especially fond of a purple mushroom called Lepista nuda for decoration. A Golden Bowerbird bower on the Atherton Tableland is well decorated with a mould-like fungus called Clavulicium extendens which grows as a pure white coat over dead twigs. The Bowerbird seems to collect small fragments of the white twigs to highlight the bower.
Bowerbirds are also fond of the yellow-green lichen called Usnea pulvinata. This is the moss-like lichen frequently seen hanging in tufts or tassels from tree branches in the wet, high humidity regions of the Tablelands. Lichens are a symbiotic relationship between a fungus and an algae in the same way as mycorrhizae are a symbiotic fungus associated with a tree or shrub.
Many birds incorporate fungi into their nests as binding material. Some fungi produce root-like strings of mycelia called rhizomorphs (rhizo = root, morph = form) and these are used like string to aid in nest construction by Willy Wagtail, Brown Honeyeater, Apostlebird, Grey Fantail and Spice Finch (aka Nutmeg Mannikin). An article by Frances Guard (2021) in Birdlife Northern Queensland Contact Call Vol. 10(2) discussed the use of rhizomorphs in some detail. Some birds incorporate lichen fungi into nests to aid in camouflage. Spectacled Monarch, Black-fronted Monarch and Eastern Yellow Robin are examples.
Inadvertently, many birds are consumers and distributers of endophytic fungi. Birds feed on petals, buds, seeds, fruit and leaves of plants, all of which contain endophytic fungi.
The host plant provides a protective sanctuary for the fungi and feeds them sugars. In return, endophytes produce a huge range of chemicals, some being well known, such as petal and fruit pigments; communication fragrances (flower perfumes); flavours (think mangoes, strawberries, apples); hormones (many of which are extracted from flowers for the perfume industry); and toxins, eg caffeine, nicotine, menthol, camphor, tannin, etc. These chemicals are used by the plant in defence against insect or pathogen attack.
We think of these substances as made by plants, but, in reality, most are made by the fungi that live inside the plant. When birds such as Torresian Imperial-Pigeons, Wompoo Fruit-Doves, or Metallic Starlings eat fruit and then poop the seeds out elsewhere, they are distributing the seeds but also passing on the endophytic fungi the seeds contain. Some fungal spores are also mixed in with pollen or nectar and are distributed by birds that feed on them.
Dispersal of fungi by birds is not just limited to local feeding ranges. There are myriads of marine fungi: especially yeasts; mycorrhizal fungi on mangroves, seaweeds and sea-grasses; and numerous pathogenic fungi that are parasites or live on dead or dying seaside plants and mangroves.
Long-range dispersers such as the many waders that migrate annually between the northern and southern hemispheres, carry spores in their gut, on their feathers, or in mud on their feet, transporting those spores across the globe. It is not coincidence, for example, that many mangrove pathogens and endophytes are found right along the Pacific Rim from Russia, through Japan, and Indonesia to Australia and New Zealand.
It is worth mentioning that Wallace’s Line in Indonesia relates not just to bird distributions but is matched by fungi that are associated with those birds.
Fungal diseases of birds should also be mentioned. There are vast numbers of fungal diseases, but most attack the bird’s lungs and other soft, moist tissues such as the eyes. Fungal diseases in wild bird populations are infrequent, but are increasing out of control in cities where bird feeders, and random scattering of bread and seed, encourages wild birds to congregate, or domesticated species such as pigeons to accumulate. Most of these fungal diseases are spread by physical contact and several are also contagious to humans, especially to children who handle pet birds. Some, such as Histoplasmosis and Aspergillosus, can be fatal.
Finally, many of us are aware that bird populations are declining globally. Our first response is usually to blame land clearing for agriculture and housing, hunting and the wildlife trade as the culprits, but there is an even greater danger from global climate change. The warming climate is killing and altering the activities of endophytic fungi, and this is changing the fragrances of flowers and the taste of nectars and fruits. This, in turn is making these foods unattractive to birds and pollinating insects, so both sugar and insect food sources are declining.
Rising temperatures are also increasing fungal pathogens that attack insects, thereby reducing food for insectivores. Likewise, the altered climate is killing or altering mycorrhizal fungi, leading to a decline in plant health, and less flowering, fruit and seed set. A decrease in numbers of insectivores, nectarivores, frugivores and granivores then results in a loss of raptors and nocturnal birds of prey.
Boddy, L. et al. (2013). Climate variation effects on fungal fruiting, Fungal Ecology (2013), http://dx.doi.org/10.1016/j.funeco.2013.10.006
Fisher, MC. et al. (2020). Threats posed by the fungal kingdom to humans, wildlife, and agriculture. mBio 11:e00449-20. doi.org/10.1128/mBio.00449-20
Article and images by Barry Muir.
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