The Daily Bucket is a regular feature of the Backyard Science group. It is a place to note any observations you have made of the world around you. Rain, sun, wind...insects, birds, flowers...meteorites, rocks...seasonal changes...all are worthy additions to the bucket. Please let us know what is going on around you in a comment. Include, as close as is comfortable for you, where you are located. Each note is a record that we can refer to in the future as we try to understand the patterns that are quietly unwinding around us.
A cold winter's north wind directed me out to a SE-facing bay nearby for my afternoon walk a few days ago. I could see waves crashing onto a small island in the distance, the wind-driven surface swells coming up the Strait hitting it full force. In the bay here it was quieter, and I was hoping to see birds, who often take refuge in sheltered spots like this in winter storms.
Keening calls caught my attention. In seconds, a flock of Black Oystercatchers circled in, landing on the beach below me.
Oystercatchers are as quick and busy and industrious as all shorebirds are, but most of the year they are loners or pairs, vigorously defending their stretch of shoreline. In winter most flock up, flitting from one rocky patch to another, always along the edge of the sea. As "obligate intertidal" creatures their only food source is between high and low tide, a very narrow habitat. This group of seven is a typical size in the Salish Sea. Up north in Alaska and British Columbia where most of them live, winter flocks of hundreds are common. That I'd like to see!
They breed on the ground near the intertidal too, and that can be hazardous. They must find sites free of raccoons, mink, cats, dogs and people, and even on remote offshore rocks their eggs and chicks can be snatched by gulls or raptors.
That's why I was so happy to see two young Oystercatchers in this group, hatched last summer. While black like the adults, their beaks are dark rather than bright orange and their eyes are not ringed in orange. Here a youngster lands awkwardly on a rock.
See what the adult Oystercatcher is holding at the end of its beak? That's a limpet, carried from the previous foraging site. Our Oystercatchers rarely eat oysters, and although I've seen them eat clams and mussels, limpets are their favorite prey.
(All photos by me. In Lightbox...click to enlarge)
The other young Oystercatcher is after a limpet in the surf. In spite of a wave washing over its head, the bird emerges successful!
One of the seven stands on a rock. A lookout? The rest are behind, poking into cracks extracting limpets. These small mollusks attach to a rock surface with enormous suction, pulling their cone-shaped shell down tight. The only ways to defeat a limpet are to surprise it, to lever it by hammering, or by breaking its shell. From my observations, Oystercatchers mostly use the first method, occasionally the second. There seem to be plenty of limpets here.
After a few minutes foraging, the lookout bird flew down to the group, stood for a moment and then they all lifted off simultaneously, one still holding its current catch. They flew across the bay, landed briefly on an offshore rock and continued on out of sight, the youngsters now indistinguishable from the adults.
They came and went in less than 4 minutes. More beaches to visit before sunset? I wonder if some of the adults were parents of the youngsters.
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P.S. For readers familiar with RAy, the banded Oystercatcher whose story I've been sharing in the Bucket for the past year: none of these was RAy. In fact I've been seeing RAy and his mate at their usual beach on the other side of the peninsula, by themselves. Two weeks ago they rousted out another pair of Oystercatchers foraging on their beach. On another occasion they allowed one Oystercatcher to feed freely there. But they regularly return to their territory rather than go off with a flock. I wonder if they were unsuccessful in raising chicks last summer. or?
I'm mystified and fascinated by what Oystercatchers do. There's a lot going on.
Winter Salish Sea Oystercatcher update in the Bucket today. What's going on in nature where you live?
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