A stretch of river VII: On the indeterminacy of the sign

The crows have begun their winter flocking now, as I reported to you good people 13 months ago today. Then, they flew to I knew not where. Today, I know where: here! Or, more precisely, the park across the river. Tens of thousands of crows. As nearly as i can tell, they perch in bare-limbed trees and caw at each other, then move to another tree not far away and commence to cawing again. The Canada geese, meanwhile, stand on the ground underneath the trees, looking up at them.

It's not mating season; that comes in the spring. No one seems to know exactly why crows do this in the winter. This is not exactly secretive behavior they're engaged in.

Crows can count up to 4.

In the Epic of Gilgamesh, it is a crow (or raven) that Utnampishtim releases from his boat that, when it does not return, signifies that land (or trees, at least) is emerging from the floodwaters. Some see this as the Sumerians' recognition, 10,000 years ago, of the crow's intelligence.*

But. Fascinated as I am by the reading about crows I've done today, it's actually something man-made that initially prompted this post, something that suddenly appeared this morning on "my" side of the river: a small, wooden Roman cross.

It was not there yesterday when Scruffy and I went walking at late dusk. It is a couple of feet off the footpath on the slope down to the water. It is not quite 3 feet tall, made of old, unpainted 2x4s with caked mud on them. But it is carefully, skilfully made: the upright and the horizontal piece are notched and fitted together in such a way that, apart from the edges that show it's made of two pieces, no gaps show in the join.

It has no name on it, no flowers or other mementos at its base. Whoever left it, though, also left the rocks/he used to pound it into the ground.

What does it signify? What are we passersby meant to think or do as we look at it? A cross asks us to remember either the sacrifice of Christ or that of someone whose grave or death-site it marks. I do not know what the maker of this particular cross asks me to remember.
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*Speaking of intelligence, ponder this, from the Wikipedia article on the New Caledonian crow:

It is one of a small group of animals now accepted in scientific study to be not only a tool-user, but a tool-maker. The New Caledonian Crow is also the only non-human species currently known to spontaneously make tools out of materials it does not encounter in the wild. It takes a very wide range of food items including many types of insects and other invertebrates (some caught in flight with some agility, including night-flying insects which it catches at dusk), eggs and nestlings, snails (which it drops from a height onto hard stones), and various nuts and seeds. It is known for using plant material to manufacture hooks or barbs for extracting grubs from inside logs and branches. It shows great ingenuity in the search for food.