Where do little sanderlings and sandpipers sleep at night?
To understand how shorebirds like sanderlings and sandpipers sleep— and it’s not necessarily at night! — it helps to understand their habitat.
Most shorebirds eke out a living on the edge, so to speak. They live in the place where land and water meet, in saltwater marshes. Each and every day, twice a day, the marsh’s conditions change. The tide rolls in and water becomes the backdrop; the tide recedes and the land (or mud) becomes the substrate.
Shorebirds are specialists. They feed on invertebrates that primarily live in the exposed mud. So when the tide goes out, every bird from least sandpipers to long-billed curlews has to get busy feeding. And they don’t have all day to find their food like a turkey or a cormorant. Keep in mind: the cycle of the tides is governed by the position of the Earth relative to the moon and sun. It is the gravitational pull of these massive bodies, rather than daylight and nighttime, that determine when a shorebird has time to catch a few ZZZZZs.
For example, it can be daylight but the source of a shorebird’s food can disappear at 9 a.m. (how’s that for a good morning!). Or, it could be evening but low tide isn’t until 10 p.m. that night (talk about a late dinner). This all means that shorebirds can be active or asleep day or night depending on tidal rhythm and the bird’s seasonal activity mode. Depending on when and where, these birds can have as little as 4 hours to get all the food they are going to use for the next 6 to 8 hours. And if the bird is in migration mode, as many in the Bay Area are now, this timing is even more critical .
Migration requires a huge amount of energy. To make the trip from their breeding grounds up north down to their winter homes in San Francisco bay, sandpipers like long-billed curlews, willets and sanderlings have to build up their fat deposits to make the trip. Depending on the distance and conditions of the migration a flock may have to stop once or several times, to replenish their fat deposits, before they reach their final destination. If the birds cannot find adequate sources of nutrition (mainly intertidal invertebrates) at these critical points in their journey, they can easily starve to death.
When high tide is at midday, ‘peeps’ (little shorebirds) don’t have much to do, so they go into ‘sleep mode’. They find a safe, quiet, protected place away from danger, drop their heart rate, stick their bill, and often a leg, into their down, and try to go to sleep. I say ‘try’ because during the day there is often so much going on (low flying planes, boating activity, dogs off leash, etc.) that it can be next to impossible for a little skinny 5-ounce bird to power down when it’s out in the open. This is a major reason why marshes and estuaries are so critical. For their survival these specialized birds need isolated sandbars and shoreline, reed ‘blinded’ upland flats, large, level expanses of grasses and forbs growing in a half inch of water, and long zig-zagging sloughs making mud islands coated with grasses and reeds. In a pinch even abandoned docks and mooring will do. But ultimately, these inaccessible places, marshes and estuaries are critical to the life of the ‘peeps’.
Clayton Anderson is a self taught naturalist and artist (BA drawing and painting) who leads nature experiences for a number of organizations. He is a contributing naturalist with the California Center for Natural History, and Eco-Ed program coordinator for Golden Gate Audubon. He likes spending his free time visiting wildlife refuges and eating Indian tacos.
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