The feast is on for urban wildlife in neighborhoods all over Seattle. Birds and squirrels are gorging themselves on a bigger-than-usual fall food supply.

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The vine maples are starting to glow, and the cattails are fuzzed with their soft flyaway seeds. Autumn’s seasonal feast is under way.

The green husks of chestnuts are split open, revealing the nuts within, shiny and round as castanets. Acorns roll like ball bearings on the city sidewalks as big oaks ripen and drop their seeds. And everywhere, the squirrels and Steller’s jays are busy.

Crowns of big oaks rustle as the brilliant blue birds fly their missions, gathering acorns to stash in their secret caches for winter. Squirrels seem hardly able to open their mouths wide enough, nor the crows, to pack in autumn’s bounty.

It takes an oak as long as 50 years to reach the maturity to produce acorns. In seasons with heavy production, called mast years, trees produce so much food a boomlet is detonated in the local wildlife. A bigger food supply this fall means better chances for a bumper crop of raccoons, coyotes, possums, mice, jays, squirrels and yes, rats, next year.

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Coupled in a tight coexistence, birds such as Steller’s jays depend partly on acorns for their diet. Oaks also depend on bird and squirrels to disperse their seeds.

Oaks need sunlight, so to produce the next generation they rely on animals to carry their seeds distant from the shade-casting parent tree.

Sarah Reichard, director of the University of Washington Botanic Gardens, said the warm, dry spring this year could have helped set a heavy crop of acorns and chestnuts. Most species that mast are wind-pollinated. In a rainy spring, the pollen ends up on the ground, but a dry spring makes for a good pollen set.

Stressed trees may also put on a lot of seed, in a last-ditch effort to reproduce. “They are thinking they are going to die,” said Seattle city arborist Nolan Rundquist. “If we have another dry spring and hot, stressing summer next year, the entire city will be carpeted in three inches of acorns.”

Trees such as maples, acorns and chestnuts don’t produce a heavy crop every year. Instead, the bonanza comes only every several years when conditions are just right. That the feast doesn’t come every year is better for the trees: It means in a big year, there’s more food on the table than the locals can possibly eat.

“The idea of producing lots of seeds is the organisms that eat them will come, but they won’t get them all,” Reichard said. The seeds left behind — and forgotten caches — are the trees’ best bet for the next generation.

Even as one season fades, the promise of new life next year is on the wing and afoot, tucked away in a bounty of seeds.