Monday, September 15, 2008

Preparations for Winter on the Elwha

Over the last week I spent every morning on the beach around the Elwha mouth, walking the beach and mapping my samples of PIT-tagged rocks as they move. The work itself is fairly uninteresting, just walking up and down the beach, waving an antennae and, when I get a signal from the reader, identifying and suveying the rock. The work gives me plenty of opportunity, though, to look around and observe the seasonal changes along the shoreline. This last week, the Harlequin Ducks arrived for the winter.

These beautiful birds spend the summer on the fast-moving Olympic Rivers breeding and fledging their young. This time of year they move down to the rough, rocky shoreline to spend the winter. We observed them in groups of 15 to 20, the adults clearly visible by their colorful markings, feeding in the breaking waves. Their strategy was to dive just in front of the largest breaking waves. Since the shoreline all around the mouth is made up primarily of large cobbles, they must be targeting the invertebrates that, usually, are safely under the rocks. As the breaking wave would roll over the cobbles, I assume that some were dislodged, or the invertebrates uncovered by the wave action. About 30% of the time the ducks would suface after the wave had passed by with some little morsel in its beak. Only once was I able to identify the food - a small slender gunnel.

As for me, I migrate south today, back to Santa Cruz, and start to prepare for a winter of analyzing the data collected this summer...


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