The sidewalks in my neighborhood often feature little wandering moss balls. I have noticed them often and wondered about them. In this part of England, there is a lot of moss always, on everything, everywhere; but that’s sedentary moss, unchanging, holding still - practically characterised by its year-round chilling-out-ness. Moss in the pavement cracks, growing along the buildings and front of garden wall; moss in the gardens and the corners between sidewalk and street. but the tumblemosses are not connected to the continuous belts of stay-at-home moss. They are disconnected, tumbleweeds, pilgrim wanderers: appearing suddenly on the pavement and mooching mysteriously on their own journeys. Like aquarium moss balls but without the currents of the water to justify them. They appear in the middle of the sidewalk in the middle of the town.
The children say they are Moss Children who have broken off from their Moss Family. They often pick them up and carry them around, shouting. Occasionally we have had to take them on train journeys (nobody else seems to have Tumblemoss; it seems to be around our neighborhood.) Sometimes the kids want to make terrariums or things, and so we specifically collect the Tumblemoss, since it’s clearly unrooted and not spoiling anything if we take it home(and I’d feel bad for the kids pulling up actual moss.) but the origins of Tumblemoss, or Moss Children, have always been a bit mysterious. They simply appear, like wild land Marimo, enigmatically. An empty sidewalk in the morning suddenly has a perfect round Moss Child in the afternoon.
Today I learned the secret origin of the Tumblemoss. Would you like to guess it?
Possibly helpful clues:
This is the layout of the road. Moss Children appear on the sidewalks/pavements.
The answer, as many of you guessed, is Bird Activity! Moss Children are created and dropped from above by birds, particularly corvids.
I should have said in the poll - Sometimes you’ll find moss on the ground that slides straight off of roofs, for example in a storm, or because it’s gotten too heavy for the roots to continue sticking to slanted slick roof tiles. These, however, usually don’t form cute little balls. They clearly look like they fell off something. I feel that Moss Children have slightly more mystery about them.
Moss Children are produced differently. Roof gutters especially in climates such as the UK can fill up with moss. Moss often has snacks in it. So small pieces of moss are systematically picked out of roof gutters by corvids. magpies, jackdaws, rooks and crows apparently all do it, creating small bird-beak-sized balls. They are then thrown down to the sidewalk below.
This can be really helpful (in a rainy country you really can’t have blocked gutters) and in some cases really annoying (if you have moss on your roof, corvids will often get carried away and pick at the tiles/felt.) Sometimes you can spot them doing it - other times they try to be sneaky! It took a long time before I finally managed to observe the behavior.
Like many corvid behaviors, it can be localised to specific areas, where they teach each other how to do it. Some neighborhoods will have abundant Moss Children, and other similar ones will never have any at all. However, in neighborhoods that do have them, it seems like many different species of corvids do this - in ours it is both jackdaws and magpies, suggesting that they might learn the behavior by watching each other.
You need several conditions to get Moss Children. A cold wet climate, a densely populated street oriented with their roofs creating their own shade from the sun, with gutters along the front, an educated corvid population, local moss that likes gutters and forms balls when plucked, and so on.
Thanks to all who participated.
