(Honorary) Plant of the Week – 7th December – Bird’s Nest Fungus, Cyathus olla

There has been a steady stream of interesting and informative blogs with some highlighting that we should expect the unexpected from our urban environment. A recent find of my own reinforced this message, but before I explain what I found it would be helpful to provide a brief background.

My partner used to visit a fast food outlet almost daily but coronavirus restrictions plus a desire to isolate meant that these trips ceased in March. With a recent introduction of ‘click and collect’ as part of a drive-through at the outlet changed the situation and so off we went. I am a vegetarian so it is not somewhere that appeals and there would be nothing of interest, or so I thought; I would sit quietly as we drove through to collect his order. I did not anticipate anything of interest happening.

Whilst queuing I glanced out of the car window onto some pale grey discs scattered over the wood chip mulch of the landscaped planting. Momentarily I was puzzled; they looked natural but were odd…and then it struck me; bird’s nest fungi. I rapidly vacated the car, shouting “I won’t be long”.

The cups of the bird’s nest fungi can be seen in the foreground with the queue of cars approaching the food collection point in the background.

Being much closer, I could see the many silvery grey ‘cups’ across the wood chip, some containing the spore-filled peridioles, commonly known as the ‘eggs’.  I had no more than 60 seconds before I need to get back to the car. However I saw enough to identify these as Cyathus olla, the Field Bird’s Nest Fungus*. An exciting discovery followed by a rapid decision of needing to come back later.

Later that same day, a return visit gave time for photographs (feeling slightly uncomfortable as I was being watched by a line of car drivers as they queued up for their food).

LEFT: Several Cyathus olla, some are open but the peridioles (eggs) have gone. In the lower right of the photo are some immature specimens with a membranous protective covering still in place. CENTRE: The membranous covering breaking away to reveal the peridioles within the cup. RIGHT: A mature Cyathus olla with just two peridioles remaining. The impressions of the other peridioles that have since dispersed appear on the interior as darkened crescent-shaped marks.

How a bird’s nest fungus disperses the peridioles The images below illustrate how the genus Cyathus uses the cup shaped structure for spore dispersal. Another genus Crucibulum uses a very similar method (more of that genus later). There are other genera within the UK however their technique differs.

Falling rain drops (1) strike within the ‘nest’ and splash out the peridioles (2). As the peridiole shoots out, it releases a cord with a sticky end (termed the funiculus) (2) which is used to catch onto and adhere to vegetation (3). The peridiole of spores remains attached (4) until an animal such as a rabbit eats the leaves. The spores are able to pass through unharmed in the droppings. As the animal will have likely moved to a different location, the spores will have dispersed to a new area.

The spore dispersal mechanism – see the text for explanation

There are three genera of fungi in the UK that are given the common name of bird’s nest. They are most commonly found growing on woody material lying on the ground (such as wood chips) although they can also grow on dung.

Cyathus The three UK species form a well-structured ‘cup’ and the peridioles (‘eggs’) within are grey to black in colour.  As the above photos reveal grey coloured peridioles, this is the genus Cyathus.

Crucibulum One species in the UK. The well-formed cup is more ochraceous with white peridioles. Known as the white-egg bird’s nest.

Nidularium Does not form a nice neat cup, the brown peridioles are exposed by the irregular tearing of the outer wall.

Having discovered the Cyathus olla in such a convenient location, over the coming days I took other mycologists for a viewing and it was on the fourth visit that I made a pleasant discovery. Within the area of Cyathus olla was a group of a distinctively different bird’s nest fungus with an ochre-coloured exterior and white peridioles; Crucibulum laeve (the white-egg bird’s nest fungus).

For me this was a first, an area of just a few metres with two different bird’s nest fungi, all within an urban setting.

Crucibulum laeve, clearly showing the white peridioles within the cup

For each of the visits, I along with the other fellow mycologists would crouch down or rest on our knees, examining and photographing the fungi no doubt to the curiosity of the occupants of the cars queuing no more than two metres away.

Until very recently a third species of bird’s nest fungus, Cyathus striatus the fluted bird’s nest, grew not more than a few minutes’ walk from the above two species. It is a wonderfully hairy species, with a thick matt of chocolate brown hairs on the exterior and distinctive grooves within the interior of the ‘cup’, however a search to obtain photos for this article failed to find it in its usual spot. If any reader would like to see this species, it does grow in large numbers at the Royal Botanic Gardens Edinburgh.

So, in conclusion, expect the unexpected from our urban environment.

*Recommended English Names for Fungi in the UK. A guide by Liz Holden and available through Plantlife

text and photos by Cameron Diekonigin

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