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

A crucial nesting site for bird colonies and a window seat for coastal conservation

When Charles Darwin called the islands of the Galapagos "a little world within itself," he could have been writing about Shamrock Island instead. Once part of Mustang Island, Shamrock split off more than 60 years ago after bay channelization and a major hurricane stole some of its sand. The nascent island lacks year-round predators, while boasting shallow seagrass meadows full of fish and invertebrates that draw in dolphins and more, marshlands that inundate in high tides, and shrub-filled uplands that mirror those found on Mustang.

"You have the whole gamut [on Shamrock], said Sonia Nájera, The Nature Conservancy in Texas' director of landscape initiatives, from below-sea level landscapes to ones at least a foot above sea level. And with that, you get lots of different [shelters and resources for birds and other wildlife that make the place come alive]."

Aerial view of Shamrock Island.

From February into late fall, the air at Shamrock rings with calls of breeding sooty terns, pelicans, white-faced ibises and more. The popular stopover for colonizing birds in the bay's southern edge provides species like threatened reddish egrets with safe—and much-needed—coastal nesting spots.

Shamrock's 100 acres also offer prime opportunities nearby for migratory birds to gain nutrients to raise young there. Caspian and royal terns that nest in the grasses can forage knee-deep in seagrass for sea trout, mullet, and flounder, without leaving their chicks alone for long periods. Meanwhile, divers such as pelicans can ply the deeper waters of the Bay. Other foraging spots are just a mile away in the saltwater lagoons of TNC's Francine Cohn Preserve, or in Charlie's Pasture and lagoons along Mustang's northern expanse.

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

Sonia Nájera

Director of Landscape Initiatives, The Nature Conservancy in Texas

Scenes from Shamrock Island

Plants and animals are abundant on this colonial bird nesting island.

Three white birds with orange faces and long, slender beaks sit in green vegetation.

A pink feathered bird stands bent over in shallow, calm water with its spoon-like beak in the water.

At least 8 adult brown pelicans stand in the sand on the shore, wading into ocean waters.

Two volunteers crouch near the shore, planting small, green seedlings in the sand.

Two featherless, white baby pelicans huddle together in a nest amongst green vegetation.

Two gray birds with white bellies stare off into the distance as they sit amongst green vegetation.

Two birds with brown bodies, white necks, brown crowns and orange beaks stand on a branch.

Over a dozen small white and black birds with bright orange beaks sit on nests in the sand.

Two white-colored reddish egrets sit at the top of green vegetation against a blue sky.

Five large, brown pelicans sit on low lying branches along the shore.

BIRD BIODIVERSITY: Many species, like white Ibis, nest at Shamrock Island. © Rich Kostecke

JUST ROSIE: A roseate spoonbill forages through shallow waters. © Rich Kostecke

SPECIES AT RISK: Brown pelicans are federally listed as endangered. © Rich Kostecke

MAKING A DIFFERENCE: Volunteers plant native seedlings to enhance habitat.

KEY ROOKERY: Shamrock Island is a critical nesting ground for birds. © Rich Kostecke

DISTINCTIVE COLORING: Tricolored herons, like these, have blue-gray feathers. © Rich Kostecke

ON THE HUNT: Crested caracaras feed on a variety of small animals. © Rich Kostecke

COLONIAL NESTING: Royal terns nest on the ground in the open. © Rich Kostecke

NOT SO RED: Reddish egrets can be dark gray or white in color. © Rich Kostecke

NESTING HABITAT: Brown pelicans often nest on low trees and mangroves. © Rich Kostecke

Protecting Shifting Shorelines

Shamrock Island's upland stretches, dotted with shrubs such as honey mesquite, and prickly pear and Spanish dagger, 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 some smaller waders choose to nest instead on the sandy flats that surround the island's shrubbier terrain. Among these month's-long residents are royal terns, and sooty terns and black skimmers, both of which have become relatively rare.

"Black skimmers are declining rapidly," Nájera said, adding that coastal construction 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. Shoreline erosion plummets behind the walls, allowing added seagrass to thrive. Even with such measures, though, up to 14 inches of shoreline can be lost along the island's edges annually.

Two youth conservationists crouched in the sand with an orange shovel. Green beach shrubs in the background and a calm tide coming in. — **RESTORING THE ISLAND** In addition to breakwaters, youth conservationists from the GulfCorps program have also helped conduct restoration work at Shamrock Island. © R.J. Hinkle

Accessible Testing Grounds

Shamrock's proximity to Mustang Island – yet minimal disturbance —brings hope as well, as it serves as a testing site for island restoration measures. For instance, TNC is monitoring near-shore stabilization approaches here, which include evaluating whether sediment works best to stabilize shorelines, with or without adding artificial reef units. Much of this restoration research is led by the Harte Research Institute of Texas A&M; their project evaluates which Texas coastal islands should be prioritized to restore for species survival.

Other research focuses on tagging and tracking the behavior of crested caracara that nest at Shamrock. Being predators, these colorful, majestic birds might have reduced colony numbers on-site, though that remains unclear.

We're working with partners to assess their impact on other populations, although their presence is a natural part of the region's ecology. It's all part of doing everything we can to keep Texas's natural spaces as healthy as possible.

Sonia Nájera

Director of Landscape Initiatives, The Nature Conservancy in Texas