A stand of eucalyptus trees used as nesting habitat by egrets and herons along the Petaluma River was felled Sunday night, worrying birders and environmentalists about the birds' future.

The work, planned for several years, is part of a Caltrans project to reconstruct the Highway 101-Petaluma Boulevard South interchange and widen the highway along that stretch.

David Keller of the Petaluma River Council snapped photos of construction crews working under floodlights Sunday evening, cutting down the 50- to 80-foot trees across from Shollenberger Park.

He found it suspicious that construction crews would conduct the dangerous work at night.

Safety was indeed an issue, said James Cameron, a deputy director at the Sonoma County Transportation Authority, which coordinates local transportation projects.

"I can't blame them for that perception," he said. "We did expect to have a lot of people looking at these trees. If we were to have bunches of people pull over on that off-ramp off Highway 101, it could be a safety issue" for drivers.

Bird lovers from several local Audubon Societies met multiple times with Caltrans during the planning process for the interchange project. Environmental documents were finalized in 2009.

Cameron said there were eight active egret and heron nests last year in the rookery. The previous two years, the presence of a red-tailed hawk forced the birds to nest elsewhere.

Birders have treasured the rookery because it was easily visible from Shollenberger Park, where schoolchildren and others could view the birds, eggs and chicks in their natural habitat.

The eucalyptus trees were too close to the planned construction, Cameron said, and crews needed to remove them before Feb. 15, when the birds' nesting cycle begins. Had crews waited, the project would have been delayed until the fall by the federal Migratory Bird Act, which protects nesting areas.

Environmentalists have asked Caltrans to immediately replace the trees with an equal number. The environmental documents of the project require mitigation for other riparian and river impacts, but not for the rookery, Cameron said.

He said the highway work from Windsor south to the county line is a priority, then the SCTA will focus on finding the $14 million estimated for replacement landscaping through the 101 corridor. That is expected to be at least three years out.

You can reach Staff Writer Lori A. Carter at 762-7297 or lori.carter@pressdemocrat.com