This year, a tiny shorebird that lives on sandy beaches returned to some of its former breeding locales for the first time in decades – in one instance spawning a science mystery story.
The snowy plover is a year-round resident along our coast. Its western population has been federally listed as threatened under the Endangered Species Act since 1993. In Central California many scientists, resource managers, and trained volunteers monitor plovers and work to protect their nests from predation and disturbance.
Carleton Eyster, on the staff of Point Blue Conservation Science (formerly PRBO), is one such individual. He helps study snowy plovers near Monterey. In mid-April, on a busman’s holiday of sorts, Carleton took a stroll along the shore of Stinson Beach. From habit, he scanned the sands for plovers ‒ small, sand-colored birds that most people overlook. To his amazement, Carleton detected a handful of snowy plovers grouped at a single nest. The last time this species bred at Stinson Beach, to anyone’s knowledge, was in 1983 – fully three decades ago.
Stinson is one of the Bay Area’s most popular recreational beaches, and nesting snowy plovers need some freedom from disturbance. They lay their eggs in shallow cups in the sand, and their main defense consists of camouflage and tricky behavior. This summer, wildlife on beaches may be finding more space than usual to coexist with people , and their dogs. Beaches tend to be uncommonly wide, because low storm activity last winter left lots of sand left onshore.
Yet far greater surprises were in store for the scientists watching the Stinson Beach saga. As Lynne Stenzel of Point Blue explains:
“Several aspects of this nest were unusual. First, there were five plovers in close proximity while the eggs were being laid; usually pairs are territorial around their nest. Observers identified three of these birds as females (two wore color bands); the other two were brightly plumaged males. Then, several days after the nest held the usual three eggs, a fourth egg appeared; this is uncommon though not unheard of. And two different plovers, both presumed females, took turns on the eggs for part of the 28-day incubation period. Finally, both males disappeared from the area before the eggs hatched; in snowy plovers, the male usually stays and tends the chicks.”
The biggest puzzle was that a seeming female assumed the parenting duties at Stinson Beach this year. While plover mates commonly share in incubating eggs, the female normally abandons the nest near hatching time; she may then fly off to breed again elsewhere.
The mystery plover at Stinson, after tending the one chick that hatched, has now left the scene. There’s still a chance to verify its actual gender, though ‒ because it is color-banded. Biologists often use this proven, safe method for gaining detailed insights into birds’ lives (helpful in conservation efforts). They place unique color combinations of light-weight anklets on some individuals’ legs and later record where they detect them.
The plover at issue is called “go:go” because it is wearing green over orange color bands on both the left leg and on the right leg. (The other color-banded female at Stinson was “og:yr” for orange over green on the left, yellow over red on the right.)
Says Lynne Stenzel: “We would dearly love to find “go:go” again this season ‒ best of all, mated with another plover, one whose gender can be known for certain. We’re asking observers now to watch for it up and down the coast.”
Birders who scrutinize small shorebirds on beaches this summer might want to join Carleton, Lynne, and many others, and report color-band combos seen ‒ perhaps helping solve a snowy plover mystery.
Claire Peaslee a member of the education and outreach staff at Point Blue Conservation Science (formerly PRBO). She is also a writer, improvisational theater artist, and naturalist who appears on Sedge Thomson’s radio program “West Coast Live.”