San Francisco Bay Osprey Days are being held this weekend at the Mare Island Shoreline Heritage Preserve. (Courtesy photo)

Bird enthusiasts, rejoice! Tomorrow is the first of the San Francisco Bay Osprey Days, which will continue through this weekend at the Mare Island Shoreline Heritage Preserve in Vallejo.

Ospreys— alternatively known as sea hawks or fish hawks— are raptor birds known for their fishing skills. Nesting ospreys are frequently found near waterways and lakes throughout the world, but throughout the 20th century they were not documented to have nested in the San Francisco Bay. Since 2001, however, osprey nesting sites have been more frequent throughout the Bay Area. According to the Golden Gate Audubon Society, 43 nests were monitored by volunteers in 2016, compared to fewer than 20 in 2012. Around 1999, Napa-Solano Audubon Society field guides Robin Leong— who directs the annual Benicia Christmas Bird Count— and Wally NeVille documented the first osprey nest on Mare Island.

Due to growing interest in osprey sightings, the Mare Island Heritage Trust—which manages the Mare Island Shoreline Heritage Preserve where many of the nests can be seen— began hosting Osprey Days.

“We held our first osprey day with very short notice in July 2013,” Myrna Hayes, Mare Island Heritage Trust president, said in a statement. “In talks together with our volunteers and Tony Brake and Harv Wilson from the Golden Gate Raptor Observatory, we felt like it was really important to get an event together so that we would have a jumpstart on what we needed in place for the annual nesting season. For the second year, osprey were observed migrating from their southern range in February, even earlier than the previous March and April timeframes. We timed this year’s event at the peak of nesting and fledging activity in late June. We have been seeing the numbers of nests and chicks remain stable in our Preserve where osprey are using former Navy shipbuilding cranes, now idle and abandoned lightpoles, rooftops and other structures including the most amazing one of all, a palm tree, upon which to build their nests. It is so exciting when Preserve users return from the mile walk and report their observations of nests with adults and young. This year, as really a bonus, we have nine pairs of nesting great egrets, some just a few feet off the main trail and a number of great blue herons nesting within easy view of the trail, as well. It’s all quite spectacular and very noisy!”

The free event features car and walking tours throughout all three days led by field guides from the Napa-Solano Audubon Society and the Golden Gate Raptor Observatory. Hayes will deliver a brown bag lunchtime talk at noon Friday to deliver a digital presentation discussing the issue of human disturbance to osprey nests and the natural predation by ravens. This session will provide the opportunity for brainstorming solutions to minimize human impact on osprey nests.

At 11:30 a.m. Saturday, Diane Rooney will provide information on ospreys throughout the country and beyond. At 12:45 p.m. Saturday, Brake— a volunteer Golden Gate Raptor Observatory Bay Osprey Project coordinator—will provide an update on the expansion of osprey nesting in the Bay Area. Rooney will return on Sunday at 11:15 a.m. to provide an overview of the osprey as a species throughout the world. The luncheons will consist of fish tacos, an obvious nod to the osprey’s diet, which is 99 percent fish. Digital slide shows featuring images by local photographers Sunil Singh, Eric Dugan, Bill George, Erik Halberstadt, Hank Miller, Wally NeVille, Jimmy Sarmiento, Karlyn Hiatt Lewis, Doris Sharrock, Al Bayless and Rosemary Rawcliffe will open the luncheon presentations.

On Saturday evening, there will be a gathering at the Preserve’s visitor center featuring wine and snacks, music and a campfire with s’mores from 6 to 8 p.m. when osprey are most likely to soar and call overhead.

Saturday and Sunday will feature boat trips that leave from the Vallejo Marina. According to a news release, the Saturday trip is nearly sold out but there are still limited seats available for the 9 to 11 a.m. and 1 to 3 p.m. trips on Sunday. These are the only events that require pre-registration, which is $40 per person. For reservations, call (510) 527-9622 or (800) 472-9942 or visit Dolphincharters.com.

Osprey Days will take place from Friday, June 22 to Sunday, June 24. All events are free and require no registration, barring the boat trips. The Preserve is located at the intersection of Railroad Avenue and 167 O’Hara Court on Mare Island. For more information, visit www.sfbayospreydays.org or call 249-9633.

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