R.E. Johnson 1967 Warbling Vireo April 28 Tilden Regional Park, Alameda Co., Calif. - partly cloudy, warm. A pair feed together in willows near stream so. of Jewell Lake. They seem to have a slow deliberate foraging pace. They do considerable looking before doing any feeding. Half the pecks made occurred while in flight. The bird would fly several feet & hover while picking an insect from a leaf or catkin at the tip of a branch, & them fly to a new branch to land. Thin branch tips are probably not strong enough to support the Vireo's weight and most of the greenery is located there. Several times a Vireo was seen to use the branch on which it stood to aid in manipulation of a small caterpillar captured on a preceding flight. Some feedings were followed by bill whipping.