Click through our slideshow to see how to turn a plate and a bowl into a bird feeder.

Up the hill behind my home in San Francisco, there's a small open-space preserve. It's basically a eucalyptus grove that was planted over a hundred years ago on a rocky, treeless crag. The non-native trees have been a source of debate in recent years; some people advocate cutting them down and replacing them with native shrubs. I see their point, but I favor keeping the trees for one simple reason: birds.

Birds everywhere are in trouble. Cats, climate change, and tall buildings all take a toll, but the biggest threat by far is habitat loss, according to Kenneth Rosenberg of the Cornell Lab of Ornithology. "It's a big term that includes everything from overfishing in the oceans to suburban development and agriculture eating up grasslands and forests," he told me.

Conservation is complicated. All I know is, I don't want to make life any harder for the owls, hawks, and 60-plus species of songbirds that nest in my "backyard" eucalyptus forest. In fact, I decided to provide them with some convenient snacks. I rummaged through my kitchen cabinet for a serviceable but underused plate and bowl, drilled a hole through each, and connected them with a carriage bolt. Then I hung the contraption up in a tree out back and filled it with birdseed. My feathered neighbors have been flocking to it.