High Island sits twelve feet above sea level on the upper Texas coast, in Galveston County, about an hour and a half east of Houston. It is a salt dome, geologically — a small rise in the otherwise level coastal prairie.
The island is densely wooded in live oak, hackberry, and salt-tolerant mulberry, and it is the first patch of forest a trans-Gulf migrant encounters after a six-hundred-mile overwater flight from the Yucatán.
On the morning of the fifteenth of April, a low-pressure system moved onshore from the Gulf with a wet south wind and a band of light rain. The Houston Audubon weather alert went out at 7:42 a.m. Conditions, it read, were favorable for a coastal fallout event.
By 10:30 the parking lots at Smith Oaks and Boy Scout Woods were full. Cars were parked along the shoulder of Tarpon Street for half a mile in each direction. The Houston Audubon volunteers at the gate had stopped trying to direct traffic.
A fallout, in trans-Gulf migration terminology, is a weather event in which migrating songbirds encounter adverse conditions over the water and arrive at the coast in exhausted, concentrated numbers. The birds drop into the first available cover. High Island is the first available cover.
Inside the Smith Oaks sanctuary at 11:14 a.m., the canopy held more warblers than most birders see in a season. A second-year male Blackburnian warbler in the lower hackberry stayed in one place for nearly four minutes, eating midges.
A rose-breasted grosbeak, an adult male in full plumage, sat in a fork of an old hackberry seventeen feet from the boardwalk and did not move for twenty minutes. Photographers gathered. Children were lifted. The bird preened slowly and ignored the crowd.
Cerulean warbler, in the high canopy. Bay-breasted warbler, in the mid-story. Black-throated green, three of them, working the live oak directly above the central rookery viewing platform.
The High Island rookery, a separate feature of Smith Oaks, holds a substantial breeding colony of great egret, snowy egret, roseate spoonbill, and neotropic cormorant. On most spring mornings, visitors come for the rookery and find the migrants as a bonus. On fallout days, the migrants reverse the priority.
Indigo bunting, scarlet tanager, summer tanager, Baltimore oriole. A first-year male orchard oriole in a mulberry, eating the first ripe fruit. A worm-eating warbler on the dead wood at the back of the central pond.
The birds were obviously tired. Many sat still longer than is typical. Many ate visibly and steadily. A black-throated green warbler at one point caught a small green caterpillar, swallowed it, sat for forty seconds with closed eyes, then resumed feeding.
Fallout days are uncommon at High Island. The weather conditions that produce them require south winds, often with rain, that meet the migrants over the central Gulf. In most spring weeks, the birds make landfall higher in the air column and continue inland without dropping into the coastal woods.
Houston Audubon's long-term data, kept by warden volunteers since the early 1980s, identify perhaps three to five fallout days in an average spring. The major fallouts of 1993 and 2017 each produced single-day species totals over forty warblers.
By 1:30 p.m. the wind had freshened from the southwest and the rain had stopped. Some of the birds began to lift. Several thousand visitors continued to walk the boardwalks of Smith Oaks and the adjoining Boy Scout Woods.
Marius Doyle, who had flown from Dublin to Houston the previous Tuesday for a long-planned spring migration trip, stood at the central platform and quietly closed his notebook for a moment. He said, more to himself than to anyone nearby, that he had not understood the geography of the event until now.
The geography is the point. High Island is one of perhaps six coastal patches in the upper Texas coast region that function as obligate landing sites for fallout-affected migrants. Sabine Woods, Sea Rim, Anahuac, Boy Scout Woods, Smith Oaks, and the smaller Hooks Woods.
Each is a tiny patch of forest in a coastal prairie that, on the right day, holds more songbirds per acre than any other place in North America. Each is protected by Houston Audubon or a similar regional entity. None is large enough to be self-evident on a map.
By 4:00 p.m. the wind had backed to the west and many of the migrants had lifted into the canopy and beyond. The parking lots began to thin. The egrets in the rookery continued their nest-tending, indifferent to the day's other events.
Edith Crale, who had timed the trip from Ithaca with a long check of NOAA's marine surface analysis pages, sat on a bench at the back of Smith Oaks at 4:30 with a notebook on her knee.
She had been to High Island three times before. This was the first day she had seen a true fallout. The notebook page, when she closed it, held thirty-seven warbler species and the time of each first observation.
By 6:00 the parking lot at Smith Oaks held a dozen cars. The wind had calmed. The light had turned warm and oblique. The hackberry where the rose-breasted grosbeak had spent his morning held only an indigo bunting, asleep, on the same branch.
