Birds Nest Fungi In Wood Mulch

Birds nest fungi are are a rather interesting looking fungi. They appear like tiny birds nests filled with eggs. The fungi responsible for this anomaly are a family of fungi called Nidulariaceae. There are 31 birds nest fungi in North America with 5 of them being fairly common. The colour and appearance of the nests and eggs can vary depending on the species of Nidulariaceae fungi involved. Their purpose or function in the eco system is that of decomposers of organic materials. They are harmless to plants, animals and humans. They can however become a bit of a nuisance when the fungi are ejected from wood mulches onto near by cars and houses, where they are difficult to remove.

In this photo you can see the peridioles of the birds nest fungi that have
been splashed up onto a deck. Once they are dry they will split open and release millions of fungal spores for wind dispersal.

Identification Of Birds Nest Fungi

As already mentioned the fungi appear like tiny birds nests filled with eggs. The bowl or nest like structure is called the peridium (or peridia in plural). They typically have a brown cup-like structure with a smooth interior and measure approximately 6mm-16mm (¼” to 5/8″) in width and height. Inside the nests, egg-like structures, called periodoles, appear; these fungal fruiting bodies range in size from about .7mm-1.6mm (1/32-1/16″) in width. New nests begin appearing typically early fall in moist, cool locations with lots of organic matter, such as wood mulches.

Life Cycle of Birds Nest Fungi

Fungal spores germinate in moist environments containing lots of organic materials like wood mulches, decaying plant material and animal feces. They create mycelia, which hook up with other mycelia, (basically creating a small underground network of threads) until the birds nest fungal fruiting bodies appear in early fall. The fungi forms a tiny nest-like structure, (peridium), to hold it’s fungal fruiting bodies that appear like tiny eggs in the basket (peridioles). Each of these eggs contains millions of fungal spores. While the eggs are forming a thin film is formed over the top of the nest. When the eggs are ready they are rain splashed up out of the nests by as much as 1m (3′) in height. They have a short cord attached to them that has a sticky pad on the end that helps it attach to plant material and other near by surfaces. If the plant material infected by the fungus is consumed by an animal it will pass through that animal with no harm and decompose the animals feces after it’s exit. For fungi not consumed, the eggs dry out and release their fungal spores back to the ground and the cycle begins again.

Control of Birds Nest Fungi

This fungus is beneficial to the garden and typically does not require control. It can however sometimes cause problems on a wood mulch that is located close to the house, cars or outdoor furniture, etc. In these cases switching to a living mulch will help as will raking the wood mulch and reducing irrigation. Topping up your wood mulch every year will help to reduce it’s occurrence. Surfaces covered in the fungus may be wiped clean with a bleach and water solution. That same 1 part bleach to 9 parts water solution may also be poured over the affected area in a 1 m radius of the house or car. (Note be very careful with this approach though as bleach can sterilize soil). A fungicide may be used instead but in the same way.

Photo credits: all photos were taken by the author.

References and reading resources:

Bird’s Nest Fungi – Wisconsin Horticulture

Unfolding the strategies of different bird’s nest fungi (forestfloornarrative.com)

Bird’s Nest Fungus | Crop Diseases | Farms.com

Kuo, M. (2014, February). The bird’s nest fungi. Retrieved from the MushroomExpert.Com Web site: https://www.mushroomexpert.com/birdsnests.html

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