Three thousand tons of sand was added to the nesting grounds for the least terns at Alameda Point in late February and early March. In the weeks that followed, volunteers from St. George Spirits and the Boy Scouts and Cub Scouts came out to help make the site ready for the arrival of the terns in mid-April.
Sand being delivered to the least tern nesting grounds at Alameda Point on February 25, 2016. Bay Bridge in the background.
The Water Emergency Transportation Authority (WETA) paid for enough sand to cover half of the 9.6-acre nesting area with three inches of sand, as well as for grading. The weeklong delivery of sand was a conservation mitigation requirement for the impact that WETA’s new ferry maintenance facility will have on the terns’ feeding area. As many as 12 ferries will make up to four passes per weekday through the Alameda Point Channel where the terns frequently dive for small fish.
Wind and water erosion take their toll on the sand substrate lying atop old airfield taxiway pavement, requiring periodic replenishment. This latest delivery of Angel Island coarse sand has built up the sand depth on much of the site to the point that it’s starting to feel like a real beach underfoot. Beaches are the traditional nesting habitat for terns.Continue reading “Ferry agency, volunteers help the least terns”
The 9.7-acre nesting area for the endangered California least terns at Alameda Point received a new layer of sand this year. Sixty dump truck loads of sand were delivered to the site on the old Navy airfield in March, paid for by the U.S. Fish & Wildlife Service (USFWS).
Fresh layer of sand on Alameda Point least tern nesting site. Looking south, with ships in San Francisco Bay in background.
After the sand was moved into place, USFWS and volunteers set up a numbered cinderblock grid system used for recording behavior and also distributed chick shelters and oyster shells for the chicks to use as protection from the elements and predators.
On Sunday, April 13 a dozen volunteers showed up for the last work party prior to nesting. The task of the day was distributing oyster shells around the site, which provide a nominal amount of sun protection for chicks and, in theory, helps make it more difficult for avian predators like red-tailed hawks and peregrine falcons to spot the chicks amongst all the white shells.
From now until the end of the nesting season in mid-August, volunteers will be participating in another program called the Tern Watch Program. Participants monitor behavior and watch for predators from their vehicles outside the nesting area.
Throughout the nesting season a USFWS biologist makes periodic walks through the site and places numbered plaster markers next to nests so that the number of eggs and success rates can be accurately recorded. If there are three eggs in a nest one week, for example, and one egg the next week with no chicks, it’s an indication that predators have grabbed the eggs.
Each year following the end of the nesting season in August, volunteers at monthly work parties gather up the oyster shells, the wooden A-frames, drain tiles, grid markers, and the hundreds of numbered markers used to identify nests. Clearing the site makes it easier to remove weeds and grade the sand, which can erode during rains. The volunteers pull weeds from inside and around the perimeter of the fenced-in site. The volunteer program during the non-nesting season is organized by the Golden Gate Audubon Society’s Friends of the Alameda Wildlife Reserve committee, in conjunction with the USFWS biologist in charge of the Alameda Point tern colony.
The effort to protect the least terns was begun by the Navy when nesting activities were first noticed in the 1980s. The likely reason for the terns choosing such an unlikely place to nest was the absence of people who might trample on the nests. The nesting site was chosen by the terns, not by the Navy or USFWS, and has been expanded to its current size as the colony expanded. The sandy substrate that approximates the traditional beach nesting habitat for terns is on top of old airfield pavement. Due to erosion caused by wind and rain, the sand has to be periodically replaced, as it was in 2009 and 2011.
Training sessions for this year’s Tern Watch Program will be held at the USFWS office at Alameda Point on April 26, April 30, May 28, and May 31. Volunteers do not have to be a bird expert, just be very interested in observing and reporting about them. Participants are required to attend one training session and commit to signing up for a minimum of three of the 3-hour shifts. Also required are binoculars, cell phone, and personal vehicle. Reservations for the training sessions can be made by calling Susan Euing at 510 521-9717 or by emailing susan_euing@yahoo.com. Directions and registration materials will be sent by email.
The annual Return of the Terns bus tour to the nesting area will be held on June 14 this year. The tour departs from the Crab Cove Visitor Center in Alameda. Registration required through the East Bay Regional Park District’s website or at the visitor center.
Adult least tern with chicks next to oyster shells at Alameda Point, June 15, 2013, during the Return of the Terns tour. Plaster marker with number on reverse side is to the right.April 13, 2014 work party, looking north, with Port of Oakland in background.Killdeer sitting on four eggs in the least tern nesting area on April 13, 2014. It is not uncommon for a few killdeer to nest among the terns. Killdeer lay their eggs about a month before the terns lay eggs.
Three busloads of visitors to the nesting area were treated to a great show on the annual “Return of the Terns” day, June 15. The nesting area is on the Nature Reserve, located on the airfield of the former naval air station. Adult terns could be seen busily bringing small fish to their young, and doting on the young chicks as they scampered around the sandy colony. The cool temperatures of the day made it less stressful for the young birds.
The adults will continue bringing fish to their young and watching over them until they’re ready to fly south in early August. It looks like it will turn out to be a very good year for Alameda’s least tern colony, the largest in Northern California. Another tern colony is on the Hayward shoreline. The California Least Tern is an endangered species. The colony at Alameda Point is managed by the U.S. Fish & Wildlife Service.
CA Least Tern @ Alameda Point – June 15, 2013CA Least Tern with fish at Alameda PointLeast Terns flying above the colony site at Alameda Point. Control Tower in background.
Alameda Point Environmental Report 