One Flew Over the Bird's Nest Fungi - Crucibulum parvulum and a Year in Review
- Dec 30, 2025
- 8 min read
On a crisp, clear Saturday morning, December the 20th, I went out for my last group mushroom walk of the calendar year. This walk was with the Upper Cape Naturalists Club, an informal group of naturalists from whom I’ve learned about spiders, dragonflies, darners, wasps, bees, and more since I joined the group in the late spring.
This go around, I got to share my knowledge with the group as we looked for mushrooms at the Breivogel Ponds Conservation Area in Falmouth, MA. We had a good fungal showing for mid-December, and we barely had to leave the parking lot to find our first mushroom: bird’s nest fungi (Crucibulum parvulum).
Bird’s nest fungi, which get their name from their resemblance to a bird’s nest full of eggs, are typically difficult to identify to species. In North America, they all used to be called Crucibulum laeve, but recent research has shed a little more light on the situation.
As part of our efforts with the Cape Cod Mycological Society we actually collected a sample from this very patch of mushrooms in October (the fungus is a prolific fruiter and the mushrooms can persist well into the winter, which is why they were still there in mid-December), and we sent a sample in for DNA sequencing through Mycota Labs Continental Bioblitz.
We got the results back a couple weeks ago and were able to confirm that this mushroom, which at the time we called Crucibulum laeve, is actually a sister species called Crucibulum parvulum. I added a few other highlights from our sequencing efforts at the bottom, and conclude with a nice year-end wrap up, so I hope you stay for the whole article (or just scroll right to the bottom).
Fun Facts
Like the Cannonball fungus from a month ago, these mushrooms are considered gasteroid fungi because they develop their spores inside their fruiting body (gasteroid → gastero → stomach). Unlike the cannonball fungus that uses ballistics to shoot out their spore packets, C. parvulum creates a nest-like fruiting body, with millions of spores packed into egg-like discs called peridioles, and patiently waits for a rain drop to fall into the nest and propel the spores out.
The young nests develop with a hairy lid covering the nest (known as an epiphgram) that eventually disintegrates to reveal the spores. The color and texture of this lid is a characteristic that can help differentiate between species, as C. parvulum’s is firm, hairy, and yellow while C. laeve has a fragile and sparsely-haired lid.
The peridioles can be splashed up to a meter from the cup (although most travel just a few centimeters) — a fair distance for a mushroom measured in millimeters. However, these mushrooms have an extra trick up their sleeve to spread their spores even further. Each peridiole has a sticky, filamentous tail called a funiculus (quite possibly a Top 2 mycological vocab word, right up there with “deliquesce”) that helps them stick their landing. This funiculus allows the peridioles to cling to blades of grass, and other plants, that will be browsed by animals and deposited in the animal dung at distances that originally seemed unattainable to this diminutive mushroom.
Packing spores in peridioles also provides an extra layer of protection. One study found that C. parvulum peridioles were able to germinate after being baked for six hours at 80° celcius (or 176°F), and they were also unaffected by 150 hours of exposure to direct UV radiation (Reference 2).
What I couldn’t find, however, is any information on how the fungus feels when all the eggs have flown the nest. It may seem like an evolutionary accomplishment to have all your spore packets distributed from your nest, but then you’re left with a void. It’s always “how far do your peridioles fly?”, never “how are you doing without them?”
Etymology
The genus Crucibulum comes from the Latin crucible, which means “small pot”, and is a reference to the cup-like shape of these tiny mushrooms. The species epithet parvulum comes from the Latin parvus, which means small, and the suffix -ulum confers an added emphasis on the small stature. This size comparison is in relation to the larger sister species, Crucibulum laeve.
Ecology
The fungus is saprotrophic and digests organic material in wood and soil. It is a white rot fungus, so it’s partial to the lignin in the plant cell walls of wood, however it can persist in the soil as well. They’re frequent fruiters in woodchips and seem to love the pre-macerated wood.
One study found that the sister species, Crucibulum laeve, was a key component in the breakdown of polyaromatic hydrocarbons (PAHs, complex chemicals found in crude oil and asphalt). When grown in pots with a willow (Salix viminalis), the plant and fungus broke down approximately half of the PAHs in the contaminated soils over the course of 60 days (Reference 3).
The fungus was first described in 1970 from mushrooms collected in the Canadian Rockies, Idaho, and Alaska. It wasn’t until citizen science and DNA sequencing became more prolific in the late 2010’s that we realized this species was growing on the eastern part of the continent as well. They pop up spring through fall in Northern North America, but the mushrooms can persist well into the winter.
Michael Kuo has taken a noble stab at keying out 31 different species of bird’s nest fungi if you feel called to better understand this cryptic group of charming mushrooms.
Other Highlights From Our Sequencing Efforts
Nathan Wilson, CCMS president, spearheaded this whole project. He collected and dehydrated mushrooms from CCMS walks this past summer and fall, and then hosted a “picking party” where we used tweezers to put little pieces of the mushroom in small vials to send out for sequencing. Our club, and the fungal citizen science community, owe him a big thank you for being motivated, curious, and most importantly, organized.
Out of the 96 specimens sequenced, about 60 were species that we wouldn’t have been able to ID without DNA sequencing (or high-level microscopy). We also collected two mushrooms that were sequenced for the first time, both found growing out of sphagnum moss in White Cedar swamps.
When a fungus is new to science, it gets placed with a provisional name that correlates to the state it was found in, and the number of other undescribed species we know of in that genus in the state. For example, the third undescribed Mycena mushroom from Massachusetts would be Mycena sp. ‘MA03’. The names are not sexy, they usually sound like a model of vacuum, but they bare this moniker until they are formally described in a scientific paper. This is a whole different, onerous process. Regardless, here are a few of the DNA highlights of mushrooms the club found this year:
Leccinum sp. ‘IN02’
I wrote about the Foxy Bolete on 11/2 and noted that we need more sequenced specimens. There was only one sequenced specimen documented on Cape Cod to this point. Well, we sequenced two Leccinum, one found in June and one found in October, and both came back as the same, yet-to-be-described species with the provisional name, Leccinum sp. ‘IN02’. This matches the previously sequenced Leccinum from the Cape, so it looks like this sp. ‘IN02’ is the species we have on the Cape that associates with pitch pine. I did a little more digging, and found that these ‘IN02’ seem to be a group of species, so then I stopped digging.
Mycena sp. ‘metata-MA01’
This small Mycena was growing out of the sphagnum moss along the Atlantic White Cedar Swamp Trail out at the Cape Cod National Seashore. This was found in June, and is similar to the species Mycena metata, a fairly non-descript bonnet mushroom, but there is enough genetic variation to constitute a new species in the specimen we found in Wellfleet, MA.
Hygrocybe sp. ‘MA01’
Quite possibly the most colorful mushroom we sequenced, these were found in a different Atlantic White Cedar Swamp. These unique ecosystems appear to be troves of fungal diversity. I actually didn’t get a picture of them because I think I had succumbed to mosquito bites by that point, so there’s good insect activity too. This mushroom looks like Hygrocybe cantharellus, and that’s what we thought it was, but DNA sequencing revealed it is a previously undocumented species.
Looking Back, Moving Forward
The large batch of DNA results was a nice way to cap off the calendar year for the Cape Cod Mycological Society, and it was also a productive year for expanding the newsletter. I interviewed five different people: Rich, Patty, Nathan, Lindsay, and Larry; and I wrote about six different forays/festivals: Morelfest, the Maine Fungus Festival, the Telluride Mushroom Festival, the COMA Clark Rogerson Foray, the NEMF Sam Ristich Foray, and the Puerto Rico Foray.
My three favorite pieces I wrote this year were Les Champignons de Paris, Toadstools and Trailtales, and In Memoriam and Mushrooms. These were a treat to write, they just flowed right out of the fingertips.
My three favorite mushrooms (based upon my stoke levels when I found them): Matsutake (Tricholoma magnivelare), Charcoal Eyelash Cups (Anthracobia melaloma), and Ophiocordyceps Stylophora.
The plan for the upcoming year is for Ciara and I to thru-hike the Appalachian Trail from mid-April through August/early September. I want to document the fungi we find along the way and compile them into a book that weaves trail narrative and mushroom education. I plan to keep the email publication going during that time with some prewritten articles, and some updates from the trail.
Most importantly, thank you for reading and learning with me as we go. I’m excited to see what 2026 has in store for us. Have a terrific New Year,
Aubrey
References:
Brodie, Harold. (2011). Crucibulum parvulum, a very small new bird’s nest fungus from northwestern North America. Canadian Journal of Botany. 48. 847-849. 10.1139/b70-116.
Nattapol Kraisitudomsook, Elena Karlsen-Ayala, Matthew E. Smith,
Unbreakable: Bird’s nest fungi tolerate extreme abiotic stresses,
Fungal Ecology, Volume 77, 2025, 101450, ISSN 1754-5048,
Ma X, Li X, Liu J, Cheng Y, Zhai F, Sun Z, Han L. Enhancing Salix viminalis L.-mediated phytoremediation of polycyclic aromatic hydrocarbon-contaminated soil by inoculation with Crucibulum laeve (white-rot fungus). Environ Sci Pollut Res Int. 2020 Nov;27(33):41326-41341. doi: 10.1007/s11356-020-10125-3. Epub 2020 Jul 17. PMID: 32681334.
Hassett MO, Fischer MW, Money NP. Short-range splash discharge of peridioles in Nidularia. Fungal Biol. 2015 Jun;119(6):471-5. doi: 10.1016/j.funbio.2015.01.003. Epub 2015 Jan 29. PMID: 25986543.