Bird's Nest Fungus

Image: Monica R.

Teeny bird nests with tiny eggs in! Are the fairies raising chickens now?

We're looking at Bird's Nest Fungi, an assortment of species in the Nidulariaceae family.

I don't know if it's because of Easter or if it's my own struggle with the dreaded sweet tooth, but I'm just seeing CHOCOLATE.

Image: quas

Are these eggs? Or a pile of chocolates in crisp, sugar shells, like Smarties and Vice Versas and M&Ms.

Image: jan parie

Nests? Or Ferrero Rocher wrappers? A whole lot of Ferrero Rocher wrappers. Someone's been hitting the chocolate, hard! You'll regret it in the morning...

Or maybe not. These nests are like 1 cm (half an inch) across! Can you imagine how disappointing it would be to search high and low on your Easter egg hunt only to find these tiny droplets of chocolate rolling around in a thimble? I can. The thought of not enough chocolate keeps me up at night. Imagine going to the shops and seeing empty shelves where the chocolate should be!

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Hold Me!

Video: RainstormGB

Bird's Nest Fungi can be found pretty well all over the world, growing on the rotting wood they feed on.

There are numerous species split into 5 genera which can be told apart by the colour of their eggs (dark chocolate, milk chocolate, white chocolate, etc.) and the shape and colour of the nest (marzipan vase, chocolate urn, toffee cup, etc.). Most of them work in a similar way, though.

If you want to sound like a huge pedant you can insist on everyone calling them "peridioles in a peridium" instead of "eggs in a nest". You can also decapitate and skin the Easter bunny to show all the children there's a man hidden inside. Just make sure there really is a man hidden inside, first.

Image: John Roper
Cyathus striatus, one of about 45 species in that genus.
The other genera have just 2 to 6 species each

The peridioles are still quite a lot like eggs, with a hard outer surface surrounding lots of spores within. New fungi will grow from these spores, so the point here is to disperse those peridioles in the hope that some spores will land somewhere with enough food.

This is where the nest comes in. Species of the genera Crucibulum and Cyathus have the best ones. Their nests are crucible or trumpet shaped, with the inner walls growing at a 70 to 75° angle with the floor. This precision is not for nothing.

Video: nikohio
Yes, they did experiments (pdf)

The point is not to send the eggs across, but up.

When it rains, raindrops smash into the carefully-angled inner wall, slosh down to the bottom of the nest and swish back up along walls, taking some of the eggs with them. The eggs are sent flying at speeds of up to 3.6 metres per second (12 feet per second), travelling several feet up into the air. For the Bird's Nest Fungus this is a good thing, which is just one of numerous differences between they and actual bird nests.

Video: CUPlantPathPhotoLab
Immature Bird's Nests are covered in a thin film to keep out the rain until they're ready

It doesn't end there, though. The eggs are actually attached to their nest by a hollow stalk which easily ruptures in the face of the irresistible power of a raindrop. Part of the stalk remains attached to the egg, and inside it is a tiny, coiled up thread called the funicular cord, which has a sticky blob on the end called the hapteron.

The hapteron adheres to any leaf or twig it bumps into.

Image: Robert Sasata
An egg. More complicated than you thought!

The egg keeps going as the funicular cord uncoils and stretches to several inches in length. But airborne adventures are soon put to an end as the hapteron maintains its hold, and the egg and its funicular cord end up getting wound around a stem or otherwise entangled among plants.

The egg can now just dry up and wither away, releasing spores into the wind. This is particularly effective given that it's dangling from a twig several feet above the ground. Crafty! Alternatively, the outer layers of the egg may be strong enough to allow it to survive a trip through a herbivore's digestive tract. Good thing it's stuck to a tasty, green plant rather than laying about on a bit of rotting wood!

Other species are slightly different in various ways. Nests of the genus Nidula have sides that are almost vertical before flaring out at the top. Some of those in Mycocalia and Nidularia hardly have proper nests at all...

Image: Sava Krstic
Nidularia deformis. Deformed is right...

They just look like a lumpy mess. Nidularia don't have those fancy funicular cords, either. Their eggs just swim in a sticky, gelatinous mass.

That's the thing with mushrooms. Whenever you see a few species with precise, expertly devised dispersal mechanisms, there's almost always a few related ones that get by with the bargain basement version. Cheap skates.

Image: Douglas Smith
Nidula niveotomentosa

I'll finish with a fruity fact. Bird's Nest Fungi of the genus Nidula produce a chemical compound called 4-(p-hydroxyphenyl)-2-butanone. Wow. That's a bit like saying "1-part-butter 2-parts-sugar 3-parts-flour..." and so on instead of "cake". At least 4-(p-hydroxyphenyl)-2-butanone has been blessed with a common name: raspberry ketone.

Raspberry ketone occurs in several fruit and it's the main thing responsible for the smell and flavour of raspberries. These days it's added to foods and perfumes for that delightful, fruity aroma. Also there was a study where it caused weight loss in mice, so a whole bunch of people are basically conducting an enormous experiment known as the "raspberry ketone diet craze" to see if it does the same in humans and if it has side effects.

It's strange to find it milling around in a fungus, but chocolate drops in a fudge barrel with a hint of raspberry? Sounds lovely!