There's an assortment of bird feeders outside. Most have cages around them, to keep unwanted wildlife out and to let only certain, small birds in; a strange inversion of the cages used to hold canaries and budgerigars as captive pets. Here, wild, feeding things are free to come and go as they please.

The mesh on these cages is too narrow for some birds. Two local woodpeckers, their breast feathers finely tuned with stars, are simply too plump to fit. For them, a single, open-sided box of suet and seed hangs at the very top of the feeding pole.

Sometimes they eat alone, sometimes as a pair. One has a red patch like a low desert sun on its chest. When they arrive at the feeder together, they mirror one another's beauty in a straightforward way that reminds you there's always something out there.

I find it hard not to stand at the window and watch, but I also find it hard not to spoil them with my presence. Sometimes, only one will spook and fly; other times they both panic together, tied to one another's instinct. If I stand motionless in the centre of the room, the distance seems to be enough, but I always try to walk closer, because I want to see those small stars and that red desert sun in as much detail as possible, and at some point I become a looming figure behind the glass, and it's too much for them.

When they leave, I briefly wonder where. Strange to think they're somewhere now, probably alive, likely to return tomorrow, but until then they will live unimaginable lives, invisible, or watched through other people's windows. I guess that's one of the thrills of birdwatching, or encountering any animal that you think is worth feeling moved by - knowing that your paths are only crossing for a brief speck. The rest is all unseen.

In King Kong (1933), the people on the island build a vast wall to keep Kong out, but they also build a vast door, large enough to let him through. They give themselves a deliberate weak spot, a window of vulnerability. This door, of course, is eventually broken down, and through it Kong enters the wider world; trains and tall buildings, sedatives and skyscrapers and chains and biplanes peppering him with holes.

My dad pointed out this design flaw the first time I ever saw the film. I didn't think it particularly interesting back then. As a child, I was too preoccupied with Kong stamping villagers into the jungle mud, drowning them slowly under his huge feet. But as an adult, I've found that huge, ill-advised door increasingly interesting, though I haven't seen the film for decades.

We let things in through doors, even ones we tell ourselves we've closed. I don't how true this is, or if we should worry about it. We build strange cages, filled with food, admitting certain pockets of wonder, and let the squirrels and the raccoons starve, though of course they never do.

In a different place, I came across a complicated photo album, designed like a bird cage. Each hole in the bars was a frame. Each frame contained a photograph. I've always thought of photographs as windows looking onto completely static views.

Outside, elsewhere, I saw another bird, small enough to flit in and out of most cages, and behind it a huge sycamore tree without leaves, contorting in the wind and lit sharp by a high sun, and I thought of those branches as roots fusing with the silhouette of the bird, converging and passing through it, as if it were a door, a door that didn't have to be there, but was.