Black Oystercatchers of the Rocky Pacific Coast

There's really never a bad time to visit California's magnificent coastline.  However, if you visit during the fall, winter and spring months, you will be treated to a wide and varied array of avian species, the numbers of which diminish in the early summer as many species return to distant breeding grounds.  (In other words, head to the coast now!)  The species composition of any given area is constantly in flux, due to the migratory nature of many birds.  This is part of what makes birding fun: Are we expecting to see migratory species today?  Breeding species?  Overwintering species?  

While some species only make brief appearances at specific times of the year, others are reliably seen in favorable habitat year-round.  One such resident of our coastline is the Black Oystercatcher (Haematopus bachmani).

The Black Oystercatcher is certainly a distinct-looking bird!  A year-round resident and breeder on rocky shores of the Pacific Coast from Alaska to Baja, these large, gull-sized birds are sure to capture the attention of birders and naturalists with their dazzling red bills and golden eyes as they meander slowly and quietly on oddly flesh-colored legs across rocks of the intertidal region in search of mussels, limpets and other molluscs. 

Because their black bodies are designed to blend in with their rocky habitat, Black Oystercatchers are not always readily visible to the casual observer.  I blazed right on past them probably dozens of times while walking along the trail between Point Pinos and Asilomar Beach before I saw my first oystercatcher.  Now, I know better.  Take a minute to stop and quietly (using binoculars) scan the rocks for moving shapes cresting large boulders, dropping into hidden crevices, reappearing once again on a neighboring rock.  Or, on windy days, take a closer look at the leeward side of giant sea boulders and you are almost certain to find a group of oystercatchers (and other birds!) huddled together taking shelter from the wind.  When disturbed, Black Oystercatchers take to the air with a startlingly loud whistling cry that one immediately recognizes above the crashing waves.

Oystercatchers feed largely on molluscs found clinging to rocks at low tide.  Using their stout bills, they are able to pry open mussles and tear limpets from rocks.  They may also feed on urchins, crabs and marine worms when present.  Oystercatchers feed mainly during low tide when their prey is exposed; during high tide, the birds may be found resting from their labors.

Black Oystercatchers are often seen clambering over rocks in pairs.  Some believe they mate for life, together defending a breeding territory that includes a nesting area above the high tide line as well as adjacent mussel beds or other feeding grounds.  The nest of the Black Oystercatcher is little more than a scrape in the rock, gravel or shore grass, situated safely above the high tide mark and lined frugally with bits of shell and pebbles.  Though they are present year-round, Black Oystercatchers are more difficult to see during the summer breeding season when the parents spend about two months in the relative seclusion of the nest, making solitary treks to their feeding zone while they incubate their eggs and raise their young.

Because of their ground-nesting habits and dependence on the intertidal zone, Black Oystercatchers are vulnerable to habitat disturbance and loss (like many of our shorebirds restricted to such a narrow range of suitable habitat).  They are also particularly vulnerable to oil spills and other pollution of the intertidal zone on which they depend; climate change is likely to be an additional threat to their continued success.