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40 STATE OF THE ESTUARY OVERVIEW • • • • Wildlife species are some of the most critical endpoints used to assess ecosystem health. This chapter examines indicators of the health of wildlife at all levels of the estuarine ecosystem, from bottom-dwelling invertebrates in the oozes to fish, waterfowl, shorebirds and seals. As indicators, wildlife can be challenging to interpret, because the health of wildlife populations depends on myriad, often interacting, factors. For many of the wildlife populations in the Estuary, key factors are freshwater inflows; water quality; habitat extent, configuration and quality; impacts from non-native species; and food availability. Monitoring across the Estuary has become more complete over time, allowing scientists to now see how wildlife respond to changes in habitat quality and the food web, among other factors. These outcomes, measured in the lives of wild plants and animals, show how our management choices, both unintended and intended, ul- Shore crab with eggs in Sausalito. Photo: Rick Lewis timately affect the other forms of life with which we share the Estuary. Creating a healthier ecosystem for wildlife will also support a healthier environment for people. While harbor seal numbers along the adjacent coast have improved since the Marine Mammal Protection Act of 1972, Estuary harbor seal numbers have not, remaining in fair condition. Dabbling ducks are increasing across San Francisco Bay in general, while diving ducks are declining significantly in the North Bay and Central Bay. Breeding waterfowl populations in the Delta and Suisun Marsh are generally in fair condition but declining, largely due to decreases in mallards, the dominant species in both areas. Wintering populations of small-sized shorebirds are generally stable and in fair condition in San Francisco Bay. Medium and large shorebirds are in poor condition, however, declining particularly in Central and South Bays. • • • Great blue heron and great egret nest density is increasing over the long term, and nest success is fairly stable. After a steep decline across San Francisco Bay prior to 2010, Ridgway’s rail has recovered in the North Bay but populations remain low in the South Bay. Tidal marsh birds, other than Ridgway’s rails, are in fair condition across San Francisco Bay and densities have increased over time, possibly due to improving marsh conditions following restoration efforts. TA TA S S T TA L DE CISC O B AY & f the est E o u This chapter summarizes data and materials written by the authors listed on page 12 and provided in full in the technical appendix for the State of the Estuary 2015 report. Go to: http://sfestuary.org/about-the-estuary/ WATER soter/ L FR DE AN C Y & O Chapter cover photo I of S C great B A blue heron nest: Michael Baird T TA ar f the est E o u ar y y S r y S AN y ua the est of ua SUPPORTING MATERIALS TE r TA r N of the est ua SA TE FR N N TA of the est WildlifE SA SA Aquatic invertebrates and fish in the upper Estuary have been strongly L impacted by water management operations (in F R A the Sierra, Central Val- DE NCI SC O B AY & ley, and Delta) that reduce and alter the patterns of freshwater inflow, and by invasions of non-native species, among other stressors. TE y y • TA TA h t e es Native fish populations in San Francisco Bay (South, f o E T Central u t a and r TA North Bays) are generally healthy, although non-native species are increasing in the Bay. However, the health of upper Estuary native fish communities in Suisun Bay and the Delta has declined markedly during Habitat the past three decades and is now in poor condition. S A large proportion of benthic invertebrate species and individuals are now non-natives at some sites in Suisun Bay and the Delta. S TAKE HOMES • • 2015