Seasons in the Sea - A month-by-month guide to Central California sea life
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Sandy Beach; Image credit: Oregon Dept. Fish and Wildlife

Sandy beaches

in May

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Spring winds and waves rebuild beaches and dunes

In May, the Central Coast beaches are still rebuilding from winter storms with the help of small waves (which move the sand from offshore to the beach) and strong afternoon winds (which move the sand from the foreshore to the back of the beach and dunes).

[Note: following paragraphs are from April. Need to modify for May]


As spring progresses, smaller waves carry sand toward shore in waves (also known as sand bars). When one of these "waves" of sand arrives at the beach, it merges on to the existing beach. In this photo, you can see where a large wave of sand has flowed over the low, winter beach (fine gray sand) in a layer of coarse, reddish-brown sand. (Source: Kim Fulton-Bennett)
After a week or so of small surf, the first of these sand bars may have moved all the way to the beach. If you visit such a beach repeatedly over several days of small surf, you may see one of these sand bars approach the shore and then "climb" up the beach. During the next series of high tides, this sand will be washed up over the seaward edge of the beach, and may add 10 to 50 feet to the overall width of the beach.

You can often tell when one of these beach widening events has occurred because the new beach sand is often coarser than the older sand. On some beaches, this newly deposited sand will be orange or pink in color because it contains grains of a pinkish mineral called feldspar. The new beach sand may also contain deposits of sea shells, sand dollars, mole crab shells, by-the-wind sailors, or other bits flotsam.

As the newly arrived beach sand begins to dry out, the gusty afternoon winds pick up the smaller sand grains and carry them toward the back of the beach. On beaches with sand dunes, this wind-driven sand helps rebuild parts of the dunes that were eroded by winter storm waves.

The wind also creates piles up around bits of seaweed or driftwood. With the help of beach hoppers, flies, and other insects, these bits of debris begin to decompose and add organic matter to the sand. Dune plants, such as sea rocket, sprout in the enriched areas, and help hold the sand in place.

If they aren't swept away by storm waves, these small drifts of sand become higher and deeper over time, eventually growing in front of and merging with the old, eroded dunes. At the same time, the sea rocket and other dune plants must grow rapidly to keep their leaves above the accumulating sand. They particularly benefit from any late rain storms that provide water before the summer drought sets in for good.

Swooping and diving over the rebuilding beach, violet green swallows hunt flies and beach hoppers (amphipods) that live within the masses of dried kelp washed up by winter storms. These avian beach predators typically arrive on the Central Coast during March or April, after spending their winters in Southern California or mainland Mexico. By late April, you may also see cliff swallows building nests along sheltered sea cliffs, especially near the mouths of creeks or streams.

Excirolana isopods carry eggs


Beach wrack and moulted mole-crab carapaces-perfect food for Excirolana isopods. (note spiny mole crab carapace at middle right (Source: Kim Fulton-Bennett)
Nestled within the grains of sand on the rebuilding beaches are 1/4-inch-long, multilegged Excirolana isopods. Like their tide-pool-dwelling relatives described in (what month?), these beach isopods typically carry eggs in brood pouches from April through June. The female isopods release their young at the highest spring tides. Carried on the tide, the young swim out into the surf zone. [When do they return?]

After mole crabs, Excirolana isopods are probably the most common and ecological important animals living in the "swash zones" of sandy beaches. They are especially important as food for surf perch and small, scurrying beach birds such as sanderlings.

Excirolana isopods eat mostly dead mole crabs and mole-crab eggs, so you can usually find them in the same areas as mole crabs. At low tide, you may find the isopods burrowed about 1/4 inch below the surface of the wet sand (you will need a strong hand lens to see them because they are so tiny). At high tides the isopods swim around in the waves looking for cast off mole crab skeletons and other debris.

Note: These isopods have such a programmed internal clock that they daily activities follow the cycle of the tides even when they are placed in aquaria on land.

[Add info on spiny mole crabs here?]

Snowy nest locally

Snowy plovers (Charadrius alexandrinus nivous) are the only species of shore bird that commonly nests on Central Coast beaches. Unfortunately, these tiny birds must share their nesting areas with clueless humans and their canine and equine companions.

At first glance, snowy plovers look somewhat like sanderlings and sandpipers, but at six inches from beak to tail tip, they are even smaller than these other beach birds. Snowy plovers' most distinguishing marks are a black line through each eye and a black patch on each shoulder. The black shoulder patch always reminds me of an old-fashioned, starched bow-tie that has come undone.

You are most likely to see snowy plovers feeding along the dry upper portions of remote Central Coast beaches that are backed by sand dunes. Unlike sandpipers, snowy plovers don't run continuously back and forth with the waves, but make short dashes across the sand, then freeze.

When running, snowy plovers look very much like pieces of kelp or other beach debris blowing in the afternoon sea breeze. When resting or nesting, snowy plovers blend in so well with their surroundings that they become practically invisible. The little birds often crouch in small depressions in the sand for protection from April's howling sea breezes. Even tire tracks or human footprints are deep enough to provide a modicum of shelter for these tiny birds.

In March or April, snowy plovers return to the Central Coast from their winter feeding grounds in the Great Plains and other inland areas. Groups of plovers often nest along the same stretch of beach each year. From March through September, they build nests in the most exposed locations imaginable, laying eggs in shallow depressions in the sand, amidst the kelp wrack and driftwood, and just above the high tide line.

Female snowy plovers lay one to three eggs in a clutch. Exposed to the howling northwest winds, these eggs would only survive for an hour or two without a parent bird sitting on them to keep them warm. During the daytime, female plovers incubate the eggs while the males forage for food. At night they trade places.

Unfortunately, many of the beaches were snowy plovers nest are also very popular with humans during the summer months. Because snowy plover eggs and nests are so tiny and well camouflaged, it is very easy for humans to walk past nests or even step on them without even noticing.

Even seemingly innocuous human activities, such as sunbathing, camping, picnicking, playing catch, or flying kites can frighten snowy plovers from their nests. At first the nesting plover may try to chase or lure the human intruder away from its nest. If this doesn't work, the bird will leave its nest will not return the intruder is at least 300 feet away. This leaves the plover's eggs exposed to the cold wind, as well as to predators such as dogs, gulls, crows, ravens, skunks, and foxes.

If a snowy plover's eggs are not stepped on, abandoned, or eaten, the young will hatch in about 27 days. Within a few hours of hatching, the young downy chicks will be dashing across the sand on spindly little legs, hunting for insects and beach hoppers. In another month, the young plovers will be on their own, and the female plover may try to nest again. In August or September, most plovers will leave the Central Coast and fly back to their winter feeding areas.

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