Every winter at the Richardson Bay Audubon Center & Sanctuary, our staff keeps a steady record of the birds that we see on our sanctuary waters. Our situation is unique in San Francisco Bay in that our sanctuary extends out into the water itself, and so we feel a special need to watch over these birds. Among the ones that we see the most often are the Greater Scaup and the Lesser Scaup (by the way, that’s a Greater Scaup pictured above in the photo by the USFWS). These birds are a little tricky to tell apart — Lesser Scaup are slightly smaller, have a bump on the back of their heads, and s smaller black tip on their beaks, among other differences. The Lesser Scaup would also seem to be significantly more widespread in terms of its winter use of the Lower 48 — imagine a U-shape encompassing most of the coastal states and well as the entire lower center. Greater Scaup seem to stick much tighter to the coastlines and Mexico. When spring approaches, the scaup leave Richardson Bay and their other wintering sites around California and elsewhere. The Greater Scaup head inland and northward to the central United States, Canada and Alaska. The Lesser Scaup almost entirely vacate the United States for Canada and Alaska, save for a few north central states. Greater Scaup will stick to the coastlines in their migration, while the Lesser Scaup will take a straight line over the ocean between Mexico and Alaska, for instance.