46 STATE OF THE ESTUARY WINTERING WATERFOWL CONTEXT Birdwatchers gazing out over the Estuary during the winter may see large flocks of ducks dipping their bills into the water or tipping upside down and diving beneath the surface. These ducks — both year round residents and migrants — spend their winters in the Estuary, which provides some of the most important win- tering habitat for waterfowl in North America. It hosts nearly half of some diving duck species that are counted in the lower Pacific Flyway during winter. The Estuary is also valuable to waterfowl during the breeding season (espe- cially in the Suisun Bay region) and during the spring and fall migratory periods. More than 30 species of waterfowl are commonly observed in the San Francisco Bay region. Waterfowl are an important part of the Estuary ecosystem and the aquatic food web, consuming both plants and invertebrates. In addition, duck hunting is an important economic and recreational activity. INDICATOR This win- 2015 back, goldeneye (Barrow’s and common), ruddy duck, scoter (black, white-winged, and surf sco- ter), and scaup (lesser and greater scaup). The indicator analyzed changes in the abundance index for all six species simultaneously, for each group (dabblers, divers). tering waterfowl indicator measures the abundance of six species of dabbling ducks and six species of diving ducks surveyed each January between 1989 and 2014 as part of the Midwin- ter Waterfowl Sur- veys. Abundance was calculated for three regions of the Estuary: North Bay, Central Bay, and South Bay. Dabbling ducks include American wigeon, gadwall, green-winged teal, mallard, Northern pintail, and North- ern shoveler. Diving ducks include Common goldeneye. Photo: Rinus Baak, USFWS bufflehead, canvas- Benchmarks derive from mean abun- dance between 1989 and 1993. The most recent five- year period (2010-2014) was compared to the benchmark. Abundance exceeding the benchmark is considered good. DETAILS INDEX OF ABUNDANCE OF SIX SPECIES NORTH BAY NORTH BAY 7 Dabblers Divers Dabblers Divers Fair Dabblers Divers Good Dabblers Divers 7 Fair Dabblers Divers 8 2013 2011 2009 2007 2005 2003 2001 2013 1999 2011 1997 2009 1995 2007 1993 2005 1991 2003 2013 1989 2001 2011 1999 2009 1997 2007 1995 2005 1993 2003 1991 2001 1989 1999 1997 1995 1993 1991 1989 Dabblers Divers 8 SOUTH BAY 9 7 0 0 9 8 2 2 10 Fair 2013 2011 2009 2007 2005 2003 2001 2013 1999 2011 1997 2009 1995 2007 1993 2005 1991 2003 2013 1989 2001 2011 1999 2009 1997 2007 1995 2005 1993 2003 1991 2001 1989 1999 0 4 4 11 10 2013 2011 2009 2007 2005 2003 2001 2013 1999 2011 1997 2009 1995 2007 1993 2005 1991 2003 2013 1989 2001 2011 1999 2009 1997 2007 1995 2005 1993 2003 1991 2001 1989 1999 1997 1995 1993 1991 1989 5 5 2 Fair 4 6 6 Fair Fair Fair Fair 7 7 SOUTH BAY 9 6 6 11 10 8 8 SOUTH BAY Good 6 11 Fair 8 10 10 CENTRAL BAY Good INDEX 8 12 Good 9 9 12 Good 10 CENTRAL BAY CENTRAL BAY Good Good 12 Good 10 10 8 11 Good 11 Dabblers Divers Dabblers Divers Dabblers Divers