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A flock of grackles invaded our yard one morning in late October. Fall migrants, I’m thinking that they use our yard as a refueling site. A last-minute snack perhaps; the trip has just begun.

The birds drop into our box elder trees to look things over, then swoop down to fill the backyard with their appetite. They come for the sunflower seeds we feed our neighborhood cardinals and chickadees.

Grackles are gluttons, but they are striking birds, shiny as new sedans, tinted bronze on their backs and wings and nape, with deep purple caps. Their eyes have bright yellow irides.

The grackles challenge each other — and any other feeder bird — for a seed perch. Grackles become more imposing up there by fluffing their body feathers to appear larger.

Quietly feeding nearby was a handful of white-throated sparrows. They are exclusive ground feeders. Grackles also feed on the ground, but the two species behave differently. The grackles feed in the open, grabbing pieces of the crushed corn I toss out there. The sparrows pick at corn along the brushy edges of the yard.

Each species is where it most likely feels comfortable. Grackles, members of the blackbird family, are birds of open spaces. They act comfortable anywhere.

Sparrows, though, are timid and cautious. They haunt shady patches, the low light a cloak to make them invisible — well, at least more difficult for a predator to see.

The grackles, dominant in the backyard world, grab leaves on the ground with their bills and flick them aside in search of food. Sparrows use their legs and feet to hop back and forth, dragging feet to expose hidden seeds.

Also good at that are fox sparrows, reddish and bulkier than the white-throats. Three of them were there that day. You sometimes can find fox sparrows along paths and trails simply by listening for rustling leaves.

The grackles fly in and out. The sparrows are present from first light to last. Now and then you can hear the white-throats singing scattered notes of their distinctive song, a faded memory of spring past.

The sparrows appear from the brush pile like magic. Snap — sparrows materialize. A mallard pushes through the weeds at pond edge to wobble-walk to the corn. Poof — sparrows disappear.

They use our supersized brush pile as cover. They rest in its tangle when not feeding.

Cardinals also feed on cracked corn. They, too, are most often seen near cover. Cardinals like brush and thicket. Being able to flit out of sight seems a constant factor for them.

Parts of our yard are messy. I believe that the more natural the yard, the more birds you’ll see there — and more species.

Two-thirds of our acre is swamp, weeds and brush. The swamp had a scattering of trees when we arrived. Now, 14 years later we have a legitimate wooded swamp.

The Realtor who handled our purchase here corrected me when I called our swamp a swamp. She told me it was a wet meadow.

Whatever, the birds like it.

Read Jim Williams’ birding blog at startribune.com/wingnut.