Birdlife of Houston, Galveston, and the Upper Texas Coast

Nesting and Migration

nesting and migration The eradication of bottomland hardwood forests has doubtless diminished the breeding populations of many Neotropical migrants. Deep forest birds such as Wood Thrush, Red-eyed Vireo, Hooded Warbler, and Summer Tanager have declined in numbers proportionate to the loss of mature bottomland forests. Nehrling (1882) characterized the American Swallowtailed Kite in Houston as “a beautiful bird, and one of the most characteristic species of this locality. Especially abundant in the bottom woods near prairies or fields.” This species has been almost eliminated as a breeding species in Texas, with the remaining scant nesting population limited to the riparian forests bordering the Sabine and Trinity rivers. Swainson’s Warbler, a species that nests in bottomlands with a cane and dwarf palmetto understory, has become decidedly rare and restricted. Interestingly, Van Remsen (1986) hypothesized that the eradication of such canebrake habitat in the southeastern United States led to the presumed extinction of Bachman’s Warbler . Perhaps the decline of Swainson’s Warbler can be attributed to the same habitat alteration. Additional Neotropical species Nehrling found nesting commonly around Houston but no longer breeding in the region include Blue-gray Gnatcatcher, Blackand -white Warbler, and Bell’s Vireo, the latter now rare throughout much of its range. The conversion of coastal prairie to agriculture (particularly rice) and urban sprawl has led to the extirpation of many grassland nesting species. Even as late as 1914 Simmons found Grasshopper Sparrow to be a common nester in the wet grasslands near Houston. Now, except for a rarely reported nest on the Katy Prairie, the species appears only during winter, as does its congener, Henslow’s Sparrow. Apparently, the relict local breeding subspecies of Henslow’s Sparrow, Ammodramus henslowii houstonensis , became extinct more than a decade ago due to the succession of its last remaining grassland to baccharis scrub. Lark Sparrows, which bred commonly in Simmons’s time, now nest only exceptionally near Houston and are a decreasing winter resident . Nehrling remarked that Cassin’s Sparrow was “a common summer resident on the open grassy prairies.” Now, to find the nearest breeding population, one must travel south to the Coastal Bend. The plight of the Attwater’s race of Greater Prairie-Chicken, our most charismatic grassland species, is discussed in more detail in the species accounts. As detailed previously, little of the original UTC habitat remains unspoiled or unaltered. Yet within this fundamentally transformed region the basic mechanics of avian migration continue to operate. Many of the Neotropical species that occur on the UTC are transient; that is, they simply pass through the region between breeding and wintering grounds. Most of these species are woodland insectivores, and the conversion of Texas coastal prairie to shrubinvaded grassland and urban woodlot has been potentially beneficial. With the continuing destruction of tropical rain forests and eastern North American woodlands, however, the importance of the isolated mottes (usually clumps of trees that dot the prairie) and cheniers (the Louisiana French term for oakcovered beach ridges) within the coastal hiatus is amplified. The preservation of the remaining UTC oak-hackberry mottes and the creation of such woodlands on coastal public lands should be given a high priority in the Neotropical Migrant Bird Conservation Program in Texas, as these isolated woodlands act as “migrant traps,” attracting birds as they move to or from their wintering grounds in Latin America. As has also already been noted, the terminal migrants that depend on mature bottomland hardwood forests and coastal grasslands for wintering and breeding have suffered their declines as a direct result of habitat modification. These two vegetation communities are the most endangered on the UTC, and every effort should be made to see that remnants are preserved and restored. For a short time, the Texas Parks and Wildlife Department attempted to restore nearly 600 acres of coastal grasslands in Galveston Island State Park. This program of burning and mowing was designed to eliminate Chinese tallow and baccharis and to return the park to its natural grassland community. Unfortunately, out-ofcontrol fires and concern from the park’s neighbors caused cessation of the burning, and mowing has nesting and migration 19 failed to restore the park’s grasslands. Similar prairie restoration projects should be initiated on additional coastal public lands, especially those where the public is less likely to hinder aggressive management practices. Remaining bottomland forests should be identified and the prospects for acquisition explored. Examples of mature bottomland forests that should be assessed for acquisition include the...