Jaeger sp. in the Contra Costa County
Today, September 17, 2012 in the Ferry Point Park, Richmond, Contra Costa County (next to Knox/Miller Shoreline Regional Park) I observed Jaeger sp. chasing tern sp. Bird presence was revealed by the loud cry of panic tern (most likely Forster's Tern). The Jaeger likely a juvenile Parasitic ((Stercorarius parasiticus), but some features are unclear, such as bicolored bill, indicating rather Pomarine (Stercorarius pomarinus). Modestly I think, that it can be rather a subadult Long-tailed Jaeger (Stercorarius longicaudus) however, I do not have a big experience in Stercorariinae, your opinions will be very helpful.
Series of 4 photos
Albert. W Linkowski