The Western gull, very similar to Herring gull, but mantle and wings are darker. A number (6-10) of juvenal gulls were seen near the water's edge, perched on baling, others foraging on mud flats. Plumage mottled greyish brown and white. Species hard to distinguish, in field. 4. Andreas herodias herodias Great blue herons. One seen wading in shallow water, on mud flats 5. Empidonax difficilis difficilis- Western flycatcher - 2 individuals heard in transition areas. 6. Olive-sided flycatcher heard not seen in first transition area traversed - north facing slope above Mill Valley. 7. Otocoris alpestris actia - California horned lark. - Heard on arid open upper sonoran hillside.