Dung-loving Bird's Nest Identification Guide

The First Impression and the Setting

Bird's nest fungi are found by people who look at the ground in detail, and this one more than most. You will be standing over a manure heap, a well-rotted dung pat in pasture, a manured vegetable bed, a stable yard, a sandy track edge, or a bed mulched with wood chip and stable waste. What you see, once your eye adjusts, is a colony of tiny cups, each only six to ten millimetres tall and four to eight millimetres wide at the mouth, packed together in dozens or hundreds over a few square centimetres of substrate. They look exactly like miniature nests holding a clutch of dark eggs.

At a glance the colony is brown and hairy when young and grey and smooth when old, and the two states often occur side by side, which can make a single patch look like two species. Get down to substrate level and use a hand lens.

Reading the Cup

The cup, properly the peridium, is the structure to interpret. In Dung-loving Bird's Nest it is a narrow inverted cone or trumpet: distinctly tapered at the base, widening evenly to the mouth, rather than a squat bowl with flaring sides, and its height a little exceeds its width.

The outer surface is the first key character. When young it is densely covered in coarse, shaggy, tawny to dark brown hairs that make the cup look felted or bristly, and those hairs often mat together into small tufts. As the fruit body weathers, the hairs wear away, and old cups become smooth, or nearly so, and fade from brown to dull grey or greyish-brown, so read this character on the youngest cups in a colony.

The inner surface is the second key character, and it is decisive. It is smooth, shining, lead-grey to blackish, and completely without grooves. Turn the cup to the light and look down inside: there must be no vertical striations, no ribs, no fluting running from mouth to base. That smooth, polished, dark inner wall is what separates this species from the commonest wood-inhabiting bird's nest.

Very young cups are closed over the top by an epiphragm, a thin whitish to buff membrane stretched across the mouth like a drumskin. It ruptures and disappears as the cup matures, so a colony will show closed, half-open and fully open cups together.

The Peridioles: the Eggs in the Nest

Inside sit the peridioles, the packets that contain the spores. In this species there are typically ten to twenty or more per cup, they are small, roughly one to two millimetres across, and they are black or blackish-brown, lens-shaped to almost spherical, smooth and lacquered-looking.

Look for the attachment. Each peridiole is joined to the cup wall by a funiculus, a fine coiled cord that is normally invisible until the peridiole is dislodged, at which point it unwinds into a long, sticky thread with a tangled adhesive tip. Tip a cup out onto a dark card and tease a peridiole away with a pin; if you can draw out a fine thread, you have confirmed the funiculate genera. There is no white outer skin on the peridiole in this species, so the dark packets sit against the dark wall.

Flesh, Texture and Colour Change

The cup wall is thin, tough, leathery to slightly brittle, and layered; sectioned with a razor it shows a hairy outer layer, a firm middle layer and a smooth dark inner lining. It does not bruise, does not exude latex and does not stain on cutting. Dried collections keep their diagnostic features for years.

Spores and How to Look at Them

A conventional spore print is not possible, because the spores are not shed from an exposed hymenium. They are sealed inside the peridioles and released only after the packet has been thrown from the cup, has stuck to vegetation, and has eventually broken down. To see the spores, crush a single peridiole on a slide under a drop of water, apply a cover slip and press.

The spores are worth the trouble here because they are unusually large. In Cyathus stercoreus they are broadly ellipsoid to almost globose, smooth, thick-walled, colourless, and in the region of twenty to thirty-five micrometres in the longest dimension, far larger than in most of the related bird's nests, which run under twenty.

Dispersal, Substrate and Season

The cup is a splash gun. A falling raindrop hitting the cup at the right angle is deflected up the flared inner wall and ejects the peridioles as much as a metre or more. As a peridiole flies, its funiculus trails behind, and the sticky tip catches on grass or a stem, whipping the packet around it so it stays fixed until it decays. The conical shape and the smooth polished interior are both refinements of this mechanism.

Look on old dung and manure, manured and composted ground, straw and stable waste, sandy soil enriched with organic matter, and increasingly on landscape wood chip and bark mulch where nutrient levels are high. It is a decomposer, breaking down dung and coarse plant fibre. The season is broad, roughly late spring through to late autumn in temperate regions, with fruiting driven by warmth and by rain following a dry spell.

Separating It From Its Look-alikes on Morphology

Cyathus striatus is the classic confusion because it is also shaggy and brown on the outside. Look inside: its inner wall is strongly and conspicuously grooved with fine vertical striations from mouth to base, and its peridioles are usually pale grey to whitish. Dung-loving Bird's Nest has a smooth, ungrooved, blackish interior and dark peridioles. Cyathus striatus is also a wood dweller, on twigs, wood chip and buried sticks rather than dung.

Cyathus olla is broader, shallower and more vase-shaped, with a distinctly wide, out-flaring, often wavy mouth. Its outer surface is only faintly downy to nearly smooth even when young, its colour is a pale grey to greyish-brown, and its peridioles are fewer, larger and grey. The silhouette alone usually settles it: olla flares, stercoreus tapers.

Crucibulum laeve is a neat, squat, cylindrical cup with a bright ochre to tawny-yellow outer surface that is finely velvety rather than shaggy, a pale yellowish epiphragm, and, decisively, whitish to buff peridioles with a distinct pale outer coat. The pale eggs in a yellow nest are unmistakable.

Nidula and Mycocalia species have peridioles that are not attached by a funiculus; they sit loose in a mucilaginous matrix, so no thread can be drawn out with a pin.

Sphaerobolus stellatus is much smaller, about two millimetres, and produces a single orange spore ball in a star-shaped cup rather than a clutch of packets.

A Working Field Sequence

Kneel and confirm the substrate is dung, manure, straw or enriched sandy ground. Check the silhouette: a narrow tapering cone, not a flaring bowl. Confirm shaggy brown hairs on young cups. Look inside for a smooth, shining, ungrooved blackish wall. Confirm many small black peridioles. Tease one out with a pin to demonstrate the funiculus. If a microscope is available, crush a peridiole and measure the unusually large spores.