Local birders are lamenting plans by Caltrans to cut down a stand of eucalyptus trees across the river from Shollenberger Park that they say is an important nesting site for great egrets and other wading birds.

The trees stand beside the site of a proposed new Petaluma Boulevard South interchange with Highway 101. Bob Dyer, a member of the Petaluma Wetlands Alliance who heads a team of three people who monitor the site, said that trees have hatched more than 400 birds over the last decade and drawn scores of wildlife lovers who have come to gaze at the elegant creatures as they nest.

Caltrans plans to cut them down by Feb. 15 as it prepares to start construction on the interchange as part of the Marin/Sonoma Narrows Highway 101 widening. The interchange project also includes replacing the bridges over the Petaluma River and, all told, will take about 3 years and $130 million to complete. Caltrans maintains that the trees must come down because they are too close to a ramp that is being built as part of the interchange, and that they must be gone by Feb. 15 so as not to hold up the project.

That's because bird nesting season officially starts on Feb. 15. After that, the agency would be required by the federal Migratory Bird Act to conduct more surveys to determine if birds were nesting in the trees. If any birds were found, the agency would have to wait until the nesting season had ended in the fall to take the trees down and begin construction.

While advocates for the trees have not given up hope that they might be saved, with the president of the Madrone Audubon Society sending a letter to Gov. Jerry Brown on Dec. 31 asking him to intervene, they have largely focused their efforts on securing funding for a replacement nesting site.

Dyer and others maintain that the environmental plan for the project requires that Caltrans replace the trees with another suitable nesting site. They are advocating for new trees to be planted as soon as possible.

"I hate to see the trees go, but if they must be taken down, we should have an immediate replacement plan," Dyer said.

However, while authorities acknowledge that mitigation is called for in the project's Environmental Impact Report, they say Caltrans will not begin replacing trees until after the project is completed — at least three years from now. In addition, the landscaping portion of the project is currently underfunded to the tune of $14 million, said James Cameron, spokesman for the Sonoma County Transportation Authority, which works with Caltrans on local highway projects. For that reason, he said, Caltrans will focus on completing the most basic landscaping requirements first, of which replacing the nesting site is not one.

That's in part because there are other rookeries, or trees that house nesting birds, in the area, Cameron said, explaining that it appears the birds have other nesting sites nearby that they could go to once the eucalyptus are removed.

Dyer acknowledged that there are other nesting sites nearby, but pointed out that the one across from Shollenberer is the only one that is easily viewed by the public.

After being approached by the Petaluma Wetlands Alliance for help, the City of Petaluma offered to provide land, either at Shollenberger Park or a neighboring wetland site, on which new nesting trees, such as cottonwoods, could be planted.

However, the city does not have money to fund the project, which is estimated to cost about $50,000.

"Bob (Dyer's) got a great group of people who has been very active and done a valiant job" of trying to save the trees," said Remleh Scherzinger of the city's public works department. He said the city would be ready to work with them if and when they develop a plan for how to fund the tree planting.

Dyer plans to continue putting pressure on the transportation agencies to "pony up" the money he says they should be required to pay.

"The EIR called for a tree replacement plan to be implemented, and I'd still like to hold them to that," he said.

(Contact Jamie Hansen at jamie.hansen@arguscourier.com.)