It’s a December phenomenon all of us should experience – watching up to 35,000 birds gather at Upper Newport Bay.

The bay is one of Southern California’s largest estuaries. In terms of biological productivity, it rivals a rainforest. The bay’s richness isn’t lost on the birds.

Traveling south from Alaska and western Canada, they rest and refuel here during long migrations. Places like Upper Newport Bay are critical habitat, like an inn along a highway.

Here, seawater mixes with fresh water, creating a dynamic estuary where tidal flow changes every six hours, either exposing or covering mudflats, fields of cordgrass and islands. Shorebirds, wading birds and waterfowl take advantage of the bay’s mudflats and salt marshes. There, they pluck, slurp or grab a meal, depending on their bill. Its shape and size determine where a bird feeds at the bay diner.

There are two easy ways to cycle from Irvine to the bay – via the Mountains to Sea Trail or San Diego Creek Trail. If you drive, you can park at the Peter and Mary Muth Interpretive Center.

Jenny Rigby is an award-winning interpretive nature planner, teacher and writer.