Abundance of Sparrows and Yellowthroats increases with greater channelization. Figure 1. Relationship of Saltmarsh Yellowthroat abundance to marsh area comprised of channels.

The effect of channelization was similar in all bay regions, apparently independent of whether the channels were artificial or natural: abundance of both Song Sparrows and Common Yellowthroats was significantly greater in marshes with more rather than fewer channels. Channelization varies in proportion to the age of a marsh: the long, undisturbed marshes at China Camp State Park are heavily channelized whereas those at Mare Island, which have developed since the cessation of World War II dockyard activities, have few channels. The wealth of channels in China Camp marshes means more feeding sites for Song Sparrows, which forage heavily in channels at low tide.

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Point Reyes Bird Observatory
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