AUDUBON RANCH GEARS UP FOR PRIME VIEWING OF HERON, EGRET NESTING RITUALS.

Byline: Michael Dougan San Francisco Examiner 

Helen Pratt hefted the tripod bearing a black spotting scope over her left shoulder and traipsed up a steep, uneven trail bordered with spring flowers called milkmaids.

Her sure-footed gait and unfettered energy belied the fact that she is one year shy of 80.

``I count seven nests,'' she announced, stopping halfway up the side of Picher Canyon to take her twice-a-week survey of the burgeoning blue heron and egret colony that assembles in the treetops each year at this time. Pratt has been keeping an eye on the great herons and their nesting pals, great and snowy egrets, since her first visit to Audubon Canyon Ranch in 1967.

A raspy caw echoed through the crooked coast redwoods that filtered Pratt's view of nearby Bolinas Lagoon. She identified the source as a raven.

``We don't like ravens very much around here,'' Pratt muttered. ``They come in late in the season and take young from the egrets' nests.''

Soon, Pratt said, as many as 100 pairs of egrets and herons will gather in the branches, engaging in elaborate courting rituals, incubating eggs and raising their young before flying off to who knows where come July.

As sure as the trees lure the birds, the birds draw people - up to 20,000 a year - during the four months that the Audubon Canyon Ranch is open to the public.

The ranch's people season continues through July 14. Grown-up visitors will be welcome on weekends and holidays only, said Executive Director Skip Schwartz, while weekdays will be devoted to hosting school groups from throughout the area.

Schwartz, who has lived on the ranch grounds for two decades, is matched only by Pratt in his enthusiasm for the visiting waterfowl.

``I love those herons,'' he said as he watched one of the first arrivals perch proudly on a distant bough as its mate soared off to feed in the lagoon. ``They're such a great bird.''

He's not alone in his devotion to the elegant inhabitants of the forest canopy. Schwartz said 300 volunteers - some of whom require 22 days of training - serve as docents and ranch guides to enrich the bird-watching experience for visitors.

That's how Pratt began 29 years ago. ``I certainly never thought I would continue until this day,'' she said. ``But there were questions I couldn't find the answers to in books.''

Like why were so many egret eggs infertile, while some adults convulsed and died? She retrieved pieces of egg still containing the yolks, as well as a few dead birds, and shipped them to a scientist who had determined that DDT contamination was threatening California's pelican population. Based on her samples, he learned that the egrets also were being decimated by pesticides in their food chain. DDT and related poisons were soon banned from widespread agricultural use, and both species have recovered.

These days, Pratt visits twice a week, climbing to three locations on each trip to identify new nests, carefully marking the locations on charts. Later in the season she will track how many eggs are laid.

Schwartz said the best location for observing the birds is an overlook a half mile up one of the trails. Visitors can sit on bleachers and look down on trees that seem to be covered with egrets and herons.

The viewing ``is great from mid-April on,'' he said. ``You see a lot of activity. You see eggs in the nests, these beautiful aquamarine eggs.''

In June, guests can watch young birds make their first awkward flights, he added. By July they start to abandon the nests.

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Photo

Photo: Skip Schwartz, director of Audubon Canyon Ranch, and volunteer Helen Pratt observe a pair of great blue herons in their treetop nest.

Associated Press