Is this a nest or a mushroom?

And what does the shape of these tiny mushrooms remind you of? A nest? If so, you're absolutely right. In English, these mushrooms are called Common bird's nest, while in Lithuanian, as often happens, the name is more modest – SMOOTH BIRDS' NEST (Latin: Crucibulum laeve). When the mushroom is young, it resembles a closed barrel, but when it matures, the upper protective layer splits open, and all the interesting bits appear! Unfortunately, I didn't get to see the newly opened barrels, as that's when "eggs" appear inside them, piled up like in a basket, looking like light-colored lentil grains or small pancakes (scientifically these eggs are called peridioles), containing spores. Fungi have various strategies to effectively spread their spores around the world. This Bird's Nest fungus has managed to utilize the kinetic energy of water – why bother itself?

Smooth Bird's Nest mushroom

When the right time comes, it uncovers its nest with these "eggs" and waits for rain, the drops of which, as they fall, eject the "eggs" from the nest. So it doesn't seem too simple, the Bird's Nest, like a clever engineer, has designed its nest so that the walls are curved at an angle that allows for the optimal amount of falling water energy to be harnessed, so that the peridioles are ejected as far as possible (sometimes they can fly over 2 m). The ejected peridioles stick to any plant they touch along the way and then wait for the right time to grow. They manage to start growing even faster if a herbivore nibbles on this egg with spores and the plant, and passes it through its digestive system – then the liberated spores can begin to grow. Well, you should look for this interesting mushroom (very carefully, as they are tiny) on decaying wood, twigs, and similar places. I found some of them on a wooden pathway in the forest!