The San Francisco Bay Bird Observatory (SFBBO), Don Edwards San Francisco Bay National Wildlife Refuge (Refuge), California Department of Fish and Game (CDFG), Hayward Area Recreational and Park District (HARD), and East Bay Regional Parks District (EBRPD) form the Western Snowy Plover Recovery Unit 3. The goal of this
collaboration is to survey former salt ponds and other habitats for Western Snowy Plovers (Charadrius alexandrinus nivosus), determine nest success of Snowy Plover nests and contribute to the management of the San Francisco Bay’s population of breeding Snowy Plovers. In 2009, we recorded Snowy Plover numbers, site use, nest success, fledging success, use of habitat enhancement projects, nest predators and avian predator numbers throughout the Snowy Plover breeding season.
During the 2009 breeding season window survey of the Pacific coast (24 May– 7 June) we counted 147 adult Snowy Plovers in the Bay. In 2009, we determined the fate 163 Snowy Plover nests in the South San Francisco Bay (South Bay). Ninety-six of the nests hatched (59%), 51 were depredated (31%), six were abandoned (3.6%), four were flooded (2.5%), three had unknown fates (1.8%) and two were lost at hatch (1.2%).
On Refuge property, we determined the fate of seven nests in the Alviso salt pond complex (pond A8, the Alviso impoundment and the dry pan area of New Chicago Marsh), 33 nests in the Ravenswood complex (ponds RSF2 and R1 – R5) and 21 nests in the Warm Springs complex (ponds A22 and A23). Out of these nests, 42 hatched (68.8%), 17 were depredated (27.8%), 1 was abandoned (1.6%) and 1 had an unknown fate (1.6%).
This year we determined the fate of 97 Snowy Plover nests at Eden Landing Ecological Reserve. Of the 97 nests, 53 hatched (55%), 32 were depredated (33%), 2 were lost at hatching (2%), 4 were flooded (4%), 5 were abandoned (5%) and 1 had an unknown fate (1%).
We determined the fate of five nests at Hayward Shoreline, one nest in the Old Oliver Brothers North salt ponds, which was depredated, and four nests on EBRPD’s Least Tern island. Out of these four nests, one was depredated by a Killdeer (Charadrius vociferous), two nests were found with broken eggs and one hatched.
Throughout the South Bay, we banded 113 chicks this breeding season. From visual observations, we determined that 28 chicks survived to fledging (24.8%) as of 30 September 2009. Using only the data where all the chicks in the brood were banded (n=29), the number of chicks fledged per male was 0.62.
During avian predator surveys we counted California Gulls (Larus californicus) and unidentified gulls as the most numerous avian predators in all areas surveyed.
SFBBO and the Refuge began a Snowy Plover habitat enhancement study beginning the winter of 2008 at Eden Landing Ecological Reserve. Enhancements consisted of oyster shells spread by hand at densities of five to eight shells/m2 over seven one ha plots. More Snowy Plovers nested in shell plots than in control plots, and nests in shell plots were more likely to hatch than all other nests not in shell plots. The highest nest density we recorded was six active nests in a one ha shell plot.
SFBBO, with the help of H.T. Harvey and Associates, deployed camera systems at Snowy Plover nests at Eden Landing. Camera systems were placed at 24 nests and recorded footage 24 hours a day. We recorded eight depredation events on film, including two separate events where California Gulls depredated a Snowy Plover nest and chicks. The camera systems also recorded Common Ravens (Corvus corax), Northern Harriers (Circus cyaneus) and Red-tailed Hawks (Buteo jamaicensis) depredating Snowy Plover nests.
The South Bay Salt Pond Restoration Project, which encompasses much of the South Bay, should continue to consider the habitat requirements of Western Snowy Plovers in the restoration planning process, including the need for large expanses of dry salt pond nesting substrate adjacent to foraging areas.
