Grab your binoculars!
When in the moisture laden undergrowth of Mt. Sutro, watered by rain or fog, listen for the insistent call of the Wilson’s warbler. Without moving a leaf, this bright yellow insect eater flits about the snowberry bushes and among the large leaves of the thimbleberry.
Here in spring and summer, the Wilson’s warbler would be impossible to find but for the insistent call. This call is made by the male as he flits rapidly from branch to branch in the dense understory of shrubs, announcing his territory. Stop, listen and train your binoculars towards the sound, a series of chirps that is unique in its insistent quality. Occasionally the male will reveal himself. Hear the call here.
The Wilson’s warbler is named for the ornithologist, Alexander Wilson who first published American Ornithology from 1808-1814, an inspiration to John James Audubon. It is a delight to see the Wilson’s warbler, a small active bird with a lemon-yellow breast, a striking black ‘yarmulke’ cap and olive-colored back and wings. He is a beauty in yellow and black. The female is less bright and lacks the black cap.
It is fun to know that a flock of warblers is known as a “bouquet”, a “confusion”, a “fall” or a “wrench” of warblers. The guide books will state that the Wilson’s warbler is ‘common in willow thickets’. Willow thickets imply streams or moisture, and an expanse of habitat that is rare in urbanized San Francisco, particularly after three years of drought. Thankfully, Mt. Sutro has the native habitat and the moisture to provide for the needs of this bird, usually found in riparian territory. After breeding and nesting here on Mount Sutro, this warbler migrates to Central America for winter and autumn living.
For more information about the Wilson’s Warbler go to: https://www.allaboutbirds.org/guide/Wilsons_Warbler/id