Shamrock Island Preserve

Shamrock Island Preserve supports a number of rare bird species, such as the state-threatened reddish egret and white-faced ibis, as well as one of the largest colonies of nesting brown pelicans. The island also has quality beach habitat for ground-nesting birds such as skimmers and four species of terns, including more than 8,000 pairs of royal terns in some years. Grassy flats can harbor an estimated 6,000 pairs of laughing gulls, while brushy uplands provide nesting structure for many other waterbirds. These nesters include great, little blue and tricolored herons, as well as black-crowned night herons, great and snowy egrets and roseate spoonbills.

Conservation efforts have helped make Shamrock Island a leading site for colonial waterbirds with breakwaters being built to protect shorelines from excessive wave action. The preserve is also farther removed from land, keeping predators such as coyotes and feral hogs from reaching the island and helping nesters be more successful.

However, the island is unusual in that it lacks a submerged sandbar just offshore. During calmer days, gentle waves generally roll across a sandbar and replenish grains of sand pulled from beaches during storms or heavier waves. Without a sandbar, erosion can steal up to 14 feet of Shamrock Island’s shoreline in a year—and if left unchecked, this erosion could seriously reduce the island's size and beaches, putting the viability of nesting on the island at risk.

Since acquiring Shamrock Island Preserve, TNC and its conservation partners have developed a long-term habitat restoration and protection program here. Much of this work hinges on the installation of 30 breakwaters just offshore, which is meant to provide a first line of defense against shoreline erosion.

The reinforced rock walls slow waves as they roll in, allowing sediment to fall from the water and settle. In addition to helping replenish sand, the protective rock walls create excellent conditions for the establishment of seagrass habitat. That seagrass helps anchor sand and sediment to the bay bottom, an additional step in baffling waves closer to shore. Future work includes breach repair of the island's shoreline and shrub restoration as a result of large-scale impacts from Winter Storm Uri in 2021.

Moreover, protecting the island from disturbance and trespassing during nesting season is one of TNC's highest priorities. When nesting birds are disturbed by visitors on the island—which causes them to leave their nests—eggs can overheat in less than three minutes. Chicks are also vulnerable to predation by laughing gulls or other predatory birds. Enhancing nesting habitat and addressing marine and bay debris, which occasionally wash up on shore, are also helping ensure the survival of the many bird species that make Shamrock Island their home.