Only two non-lichenized fungi were reported on the island in June: a bird's nest fungus and a bracket fungus.

June is a slow time for mushrooms here, especially since we had such a dry spring. Most fungal fruiting bodies use water to inflate themselves rapidly like those little animal-shaped sponge toys sold inside gelatin capsules. They don't grow when there's no rain. The tough woody textured mushrooms observed this month actually grew this spring, or perhaps even earlier.

observation by caladri

Phellinus igniarius, the willow bracket, has a cork-like texture and grows primarily on willows, like on this tree next to the stream at the centre of Ganges. It also sometimes grows on alders and birches. It does not shrivel away like water-based mushrooms. Instead, each year it adds a layer of new growth around the edge of the mushroom, so its age can be determined by cutting into it and counting the rings, like a tree. One specimen was found to be eighty years old. Another species in the same genus, Phellinus ellipsoideus, has the same add-a-layer-each-year growth pattern and has produced the largest known single fruiting body, ten meters across and weighing 400-500 kilograms!

This species feeds on the inner heartwood of trees, leaving behind soft, extra-flammable wood called "esca" or "torchwood" and giving the mushroom another common name: fire sponge. Both fruiting body and esca have been used as kindling to start fires. In serious cases, the entire interior of a tree may become hollow, even while the outside layer is still alive.

observation by dianalynn1

Woodpeckers, like this pileated woodpecker, love esca. It's much easier to dig out a nest hollow in wood that has been softened by a willow bracket or other heart rot then an unaffected tree.

Tests using instruments that see in the same colour wavelengths as woodpeckers have discovered that heart rots change the colour of trees in the ultraviolet spectrum - invisible to humans, but visible to birds. Woodpeckers would be able to see which trees have been infected and will be easy to nest in. Experiments drilling into trees looking for infection have also found that fungal infections in trees spread outward from woodpecker holes and nests, so there's evidence woodpeckers are spreading the fungus from tree to tree. The woodpeckers dig around in infected trees, get fungus spores on their beaks, and transfer those spores to infect other trees they hammer on.

So woodpeckers and heart rot fungi have a symbiotic relationships very similar to bees and flowers. The fungi make a bright colour birds can see that indicates a good place to put a nest, and then the woodpecker lives in the esca and carries fungus spores to other trees.

Humans do not find Phellinus igniarius's wine-cork texture edible, but in parts of Alaska, it was burnt and mixed with tobacco to make iqmik. The alkaline fungus ashes make nicotine more absorbable by the body, and a higher dose of nicotine is available from less tobacco. The burnt willow bracket ashes are traditionally stored in carved wooden boxes like this one.

For more information:

• O'Daniels, Sean T., et al. "Visual cues for woodpeckers: light reflectance of decayed wood varies by decay fungus." The Wilson Journal of Ornithology 130.1 (2018): 200-212.
  Experiment testing whether birds can see colour changes in the wood of trees infected by heart rots. Their results for willow bracket are inconclusive, but most other heart rots they test appear to be visible to birds.

• Conner, Richard N., Orson K. Miller Jr, and Curtis S. Adkisson. "Woodpecker dependence on trees infected by fungal heart rots." The Wilson Bulletin (1976): 575-581.
  Drills holes into trees at set intervals below woodpecker nests, looking at what fungi are spreading out from the nest, including willow bracket.

• Tom Volk describes the usage of Phellinus igniarius as iqmik