Remsen, J.V. 1974 Thick-billed Kingbird Tyrannus crassirostris Nov.26 McClaren Park, San Francisco, San Francisco Co., Calif I located by its distinctive: "chy-boo" " call, given eeee frequently as it sallredout from cypress tree tops. The bird had been present since early Nov. and Fieldmarks seen by virtually every birder in N. Calif.. The very thick bill with decurved culmen throughout its length; very dark brown mask and head; brown back wings and tail - no hint of green or rusty; whitish throat and chest becoming strongly yellow on belly, more yellowish than the field guides show for this species.