Nidularia deformis (Batsch) Pers. - Pea-shaped Bird's Nest

Phylum: Basidiomycota - Class: Agaricomycetes - Order: Agaricales - Family: Agaricaceae

Nidularia deformis, Pea-shaped Bird's Nest

Nidularia deformisis, one of several species of bird's-nest fungus, is distinguished by its chestnut-brown, vertically-squashed 'eggs', or peridioles as they are known in mycological circles. The fruitbodies grow on rotting wood or wood-rich debris in damp, shaded locations.

Nidularia deformis, Pea-shaped Bird's Nest fungus


A rare find in Britain and Ireland, these little fungi are known to occur in Scandinavia and other parts of Europe including Germany and France. This species is also recorded in North America, Australia and New Zealand.

Taxonomic history

This gasteromycete fungus was described in 1788 by German botanist Carl Ludwig Willdenow (1765 - 1812), who gave it the scientific name Cyathus deformis. The currently-accepted name Nidularia deformis dates from an 1813 publication by the Swedish mycologist Elias Magnus Fries.

Synonyms of Nidularia deformis include Cyathus deformis Willd., Granularia pisiformis Roth., Nidularia berkeleyi Massee, Nidularia confluens Fr., Nidularia farcta (Roth) Fr., Nidularia pisiformis (Roth) Tul. & C. Tul., and Nidularia radicata Fr.& Nordholm.


The generic name Nidularia comes from the Latin Nidulus, meaning 'little nest'. The specific epithet deformis is a reference to the squashed (misshapen or deformed) shape of the 'eggs'.

Identification guide

immature Nidularia deformis, Pea-shaped Bird's Nest

Fruitbody (Peridium)

Subglobose, typically 5 to 10mm diameter, cream to cinnamon-buff, thin-skinned and with a felty or scaly surface texture; filled with a gelatinous mass within which the peridioles develop; case rupturing irregularly when the peridioles reach maturity.

Mature eggs of Nidularia deformis, Pea-shaped Bird's Nest


Individual 'eggs' are round-edged biscuit-like discs 0,.5 to 2mm across and up to 0.3mm thick. The surface of an egg is chestnut brown, while its interior is white.

Each fruitbody contains a large and very variable number of peridioles, which are not attached to the base of the cup.



Broadly ellipsoidal smooth,6-10 x 4-7µm; inamyoid.

Spore colour



Not significant.

Habitat & Ecological role

Mainly found on wet rotting wood, wood-chip mulch and permanently-damp sawdust.


May to November in Britain and Ireland.

Similar species

Cyathus and Crucibulum species have regularly-opening peridia, and their peridioles are much more globose.

Culinary Notes

These fungi are reported to be inedible.

Reference Sources

, Pat O'Reilly, 2016.

Dictionary of the Fungi; Paul M. Kirk, Paul F. Cannon, David W. Minter and J. A. Stalpers; CABI, 2008

Taxonomic history and synonym information on these pages is drawn from many sources but in particular from the British Mycological Society's GB Checklist of Fungi.


This page includes pictures kindly contributed by James Langiewicz.

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