A large group of brown pelicans take flight, skimming the ocean surface. — SUPPORTING SPECIES Shamrock Island is one of the most critical bird-nesting islands in the Texas Gulf Coast. © Rich Kostecke

Shamrock Island Bird Rookery

This site provides a crucial nesting site for bird colonies and a window seat for coastal conservation.

Once part of Mustang Island, Shamrock split off more than 60 years ago after pipeline channelization and a major hurricane stole some of its sand. The nascent island boasts shallow seagrass meadows full of fish and invertebrates, marshlands that inundate in high tides and shrub-filled uplands that mirror those found in South Texas.

"You have so many different habitats on Shamrock, said Sonia Nájera, TNC's director of landscape initiatives, from below-sea level landscapes like seagrass beds to ones at least a foot above sea level, including upland brush and grasses. And with that, you get lots of different shelters and resources for birds and other wildlife that make the place come alive."

Shamrock Island Aerial view of Shamrock Island. © The Nature Conservancy

Protecting Shifting Shorelines

Shamrock Island's upland stretches, dotted with shrubs such as honey mesquite, granjeno and salt cedar, form about two thirds of the landscape. The shrubs provide above-ground nesting sites for wading birds like roseate spoonbills and reddish egrets, and thousands of brown pelicans. These pelicans, which warm their eggs using the heat off their feet, just came off the endangered species list a few years ago thanks to rookeries like Shamrock.

Gulls and terns are ground nesters, nesting instead on the sandy flats that surround the island's shrubbier terrain. Among these month's-long residents are royal terns, sandwich terns and black skimmers, which have become relatively rare.

The lower part of this bird's knife- shaped black and red bill is longer than the upper part. They feed by ‘skimming’ the water’s surface with their bills to catch small fish. — **Black skimmers** Black skimmers feed by 'skimming' the water's surface with their bills to catch small fish. © Connor Coleman

"Black skimmers are declining rapidly throughout their range," Nájera said, adding that coastal flooding, human disturbance of nesting colonies and other factors have limited nesting sites for many coastal bird species statewide.

To help retain quality sites at Shamrock, TNC and other organizations have ringed it with reinforced rock walls. These 27 breakwaters buffer the impact of wind-driven waves that stream across Corpus Christi Bay onto Shamrock. Breakwaters help maintain calm waters around the island, allowing for seagrass to thrive. Even with such measures, shoreline erosion, overtopping and breaches are a constant threat and chip away along the island's edges annually.

Shamrock is important in and of itself, but it's also part of this larger system that many species rely on.

Sonia Nájera

Director of Landscape Initiatives, The Nature Conservancy in Texas

Accessible Testing Grounds

Shamrock's importance to regional colonial nesting birds—and its proximity to Mustang Island—help it serve as a testing site for island restoration measures. For instance, TNC and partners are constructing and monitoring near-shore stabilization approaches, which include evaluating different techniques for breach repair and sediment accretion. Bird research is being led by the Harte Research Institute of Texas A&M and Coastal Bend Bays & Estuaries Program; their project evaluates which Texas coastal islands should be prioritized to restore and stabilize for population and species survival.