Sparrows uniquely adapted to Bay Area marshes are losing their uniqueness

How does loss of habitat affect the animals still living there? A genetic study of saltwater-adapted Savannah sparrows around the San Francisco Bay Area shows that the 90% loss of tidal marsh habitat has led to more interbreeding with freshwater-adapted Savannah sparrows, diminishing their genetic adaptation to saltwater, such as enlarged kidneys and larger beak. This could lessen their ability to live in a saltwater habitat.