BirdLife International and the National Audubon Society have ranked the Hillsborough Bay Important Bird Area (IBA) as a globally significant site, based on the bird populations found there.  Spoil islands in Hillsborough Bay provide key nesting, wintering, and migratory habitat for bird species.

The Alafia Bank Bird Sanctuary islands were constructed in 1929-1930.  The islands were immediately important as bird nesting habitat, at first for beach-nesting birds including gulls, terns, Black Skimmers, and American Oystercatchers, and then as a nesting site for pelicans, herons, egrets, ibis, and spoonbills.  Today it remains one of the largest nesting colonies in Florida and one of the most diverse in the United States, with 8,000-15,000 pairs of sixteen species nesting there each spring.  The White Ibis and Roseate Spoonbills that nest here constitute one of the largest colonies for these species in Florida.

Read Audubon of Florida's press release on the Hillsborough Bay IBA.