Directly above me, the silhouettes of more than a quarter million ducks and geese streamed across the dusk sky. Squawks, honks and wails filled the air. The fly-out spanned for miles.

A light rain fell across the Sacramento Valley. Less than a mile away, drivers moved along Interstate 5 at 70 or 75 mph without a clue of the spectacle occurring above them.

A few hours earlier, I filmed a family of sea otters in a slough, the liftoff of roughly 50,000 snow geese, and a one-of-a-kind hybrid, a pintail/gadwall, and figured there was no way to top it.

Then, as the last light of the day faded to gray, the ducks and geese at the Sacramento National Wildlife Refuge rose up, filled the sky and then flew directly overhead in a 20-minute stream as they ventured out of the refuge. They were probably heading out to feed for the night at the region’s rice fields.

The fly-out is symbolic of how even moderate rain in the Bay Area and Northern California this month has refreshed marsh wetlands — and just in time. Some 6 million waterfowl on the Pacific Flyway, and millions of migratory shorebirds and songbirds, are arriving in California this month to find revived habitat waiting for them.

To see the spectacle last week, I ventured to several wildlife refuges in the Sacramento Valley and lower Sacramento River Delta. Great driving tours are available to the public at the Sacramento and Colusa refuges, and another will reopen to the public in February at the Grizzly Island Wildlife Area in the lower delta near Suisun City.

A video of my trip is posted with this story at SFChronicle.com and on my Facebook page at www.facebook.com/ tomstienstraoutdoors. It’s titled, “Northern California’s Wildlife Paradise.” It has to be seen to be believed.

Just two months ago, four of the six refuges in the Sacramento National Wildlife Refuge Complex were dry. Of the two that had water, Sacramento had only 17 percent wetlands and Delevan 22 percent.

“As of this week, we’re about 95 percent flooded,” said Mike Wolder, a biologist at refuge headquarters. “In the drought, we’ve learned how to stretch the water and how the water works its way up at some of our refuges.”

The influx of birds quickly followed the water’s arrival. According to aerial surveys, the number of geese increased from 342 to 300,000, Wolder said, and the number of ducks from 120,000 to more than 1 million.

It’s a similar story in the lower delta at Grizzly Island Wildlife Area, and in the Bay Area at 20 wetlands that provide a winter home for 1.3 million waterfowl and shorebirds.

The one exception to the flourishing numbers is mallard ducks, which are California’s top resident hatched-and-raised waterfowl species. From the drought and lack of water at wetlands the past two springs, their nesting success plummeted. Mallards accounted for only 3 percent of total ducks in the latest survey, similar to previous counts.

If you are heading out of town for the holidays and in the vicinity of one of the refuges, allow an hour for a driving tour of a refuge. A short visit can do more than break up your trip. It can crown the season.

Every time I drive the wildlife tour, the results have been different, including back-to-back days last week.

One recent pattern , however, is the en masse fly-out at dusk from the Sacramento refuge complex. The exact best spot to see this is at the sharp left turn in the road near the final leg of the driving tour, Wolder confirmed.

On the driving tours, even on cloudy, rainy days, you can often see amazing numbers of birds and with binoculars or a spotting scope zoom in and watch their quirky personalities. Much of this is captured in the video I posted.

Like anybody who tries to film wildlife, I missed some stunners: As night took hold, a doe and a fawn crossed the levee road, and when I tried to take video of them, they swam in a tandem across a slough 40 feet away; it was too dark to capture.

Earlier, when I was transfixed with the hybrid pintail/gadwall, a bald eagle sailed past, in range for only a few seconds. Later, a golden eagle with a 7-foot wingspan flew right over me and I got so excited and rattled that I fumbled around and managed to record the ceiling of my truck and various sections of sky; the footage looked like I was in an earthquake.

Amid a revived landscape, these are among the episodes you never see coming.

December’s rains have arrived just in time.

Tom Stienstra is The Chronicle’s outdoor writer. E-mail: tstienstra@sfchronicle.com Twitter: @StienstraTom.

Wildlife driving tours

Sacramento National Wildlife Refuge: In the Sacramento Valley, take Interstate 5 north to the exit for County Road 68 (north of Maxwell, south of Willows). Go east to the stop sign at Old Highway 99 (east side frontage road of I-5). Turn left and drive 1.5 miles to the signed refuge entrance road on the right. Bear right on the driving tour (signed). Drive slowly and work your way along the horseshoe-shaped route around the refuge. 6-mile loop.

Colusa National Wildlife Refuge: In the Sacramento Valley, take I-5 to Williams and the exit for Highway 20 east. At the stop sign, turn right on Highway 20 and drive 6.7 miles (past Lonestar Road) to the signed exit for the driving tour on the right at O’Hair Road. Turn right and drive about 1 mile to the refuge driving tour entrance on the right. 3-mile loop.

Contact for refuges: U.S Fish and Wildlife Service, (530) 934-2801; www.fws.gov/refuge/sacramento.

Grizzly Island Wildlife Area: Open to public in early February. From the greater Bay Area, take Interstate 80 east to Fairfield and the exit for Highway 12/Rio Vista. Drive east on Highway 12 for 4.3 miles to Suisun City and the stoplight at Grizzly Island Road. Turn right and drive 9.5 miles to the Department of Fish and Wildlife check-in station (get a map here). 15 miles, out and back.

Contact for wildlife area: Grizzly Island Wildlife Area (707) 425-3828; California Department of Fish and Wildlife, www.wildlife.ca.gov/Lands

Federal duck stamp: $25, of which 98 cents of every dollar goes to the purchase of wetlands; provides free access to all National wildlife refuges; available at www.duckstamp.com.