Photos by Ron Holmes Photo by Joe Halton
A walk along the beautiful, rocky shorelines of Skagit County during summer can be a quiet relaxing moment until a parcel of Black Oystercatchers arrives. A group of these strikingly beautiful shorebirds is called a parcel. They can be heard from a distance and will quickly demand attention as they call to each other in flight and while foraging along rocky coasts. This shorebird is one of Skagit County's most interesting year-round residents.
The long red-orange bill contrasting with the black hood is an attention grabber for identification. But what color are those eyes? They can appear red or orange. Yet the eyes are really yellow with an orange eye ring. This bird sports a black hood with dark brown body and wing plumage. Legs and feet are dull light pink. The length of the adult Oystercatcher is about 18 inches with a wingspan of 32 inches. The bill is almost 4 inches long. Overall appearance is stocky. And yes, this bird has been described as “looking like a crow smoking a carrot.” Immature birds are dark brown and the bill has a black tip.
These monogamous birds stay together year-round. Their average life-span is 15 years. The oldest known bird was 30. The birds nest in a scraped depression on a rocky ledge or shoreline. Pebbles and broken shells may line the nest. Two to three buff colored brown speckled eggs are laid. If more than four eggs are in the nest, this indicates a “dump nest” being used by more than one female. The egg's shells are very hard and can even survive being briefly submerged during high tides. However, the eggs are not too hard for Ravens to prey upon. Egg predation happens frequently, so the Oystercatchers have been known to nest up to five times during a breeding season to produce a successful clutch. The chicks are precocial but are fed and must learn how to feed from the adults. To avoid predators, the young will dive underwater. They can fly within 30 days, but have been known to stay with adults for up to a year or until the next brood arrives.
These birds forage in the intertidal zone feeding on mostly mussels, limpets and chitons. Unlike their East Coast “cousins”, the American Oystercatcher, Black Oystercatchers rarely feed on oysters. Their bills are amazing tools. Scientists are have studied their “shell shucking” techniques and they fall into two groups, the stabbers and the hammerers. Stabbers sneak up on open mollusks and quickly insert their bills severing the bivalve's adductors before they can “clam up.” Hammerers dislodge the mollusk from its mooring and then proceed rapid, direct hits to one side of the bivalve. These techniques are taught to their off-spring. They also feed on barnacles, crabs and marine worms.
Black Oystercatchers are found on rocky shores and islands from the Aleutians to Baja California. Its total population is less than 12,000 birds. This species is not considered threatened, but is an environmental keystone indicator throughout its range. Habitat loss due to increased sea-lion and seal populations have effected numbers along the California coast. These birds are year-round residents along most of their range except in the northern most Aleutian Islands. They will aggressively defend their feeding grounds.
While enjoying the rocky shorelines of Skagit County listen for the sharp piercing whistle calls of Black Oystercatchers. Why so loud? Ornithologist believe it's an adaptation to be heard over crashing waves on rocks. So, be ready to hear a “parcel” this summer.
References available upon request.