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BirdsBirds The Lower Rio Grande Valley has long been known as one of, if not the, best places in the United States to watch birds. The reason for this interest is the incredible diversity and uniqueness of the birds that can be seen in such a relatively small area. A total of 485 species of birds have been recorded from the LRGV, a number that exceeds any other location of equal size north of the Mexican border. This total represents 53% of all bird species recorded in North America. In comparison, the total number of species (as of 1998) recorded in Florida is 477, and the total for the bordering state of Louisiana is 450. Only Texas (the state as a whole), California, Arizona, and New Mexico equal or exceed this total. The Tamaulipan Biotic Province and its special habitats support small populations of several "endemic" species or subspecies. These species are consistently found nowhere else in the United States. Many are restricted to a small geographic area that is related to the availability of a declining habitat such as Sabal Palm forest or riparian woodlands. Endemic subspecies within this province include: o Texas Red-shouldered Hawk o Zapata Carolina Wren o Brownsville Common Yellowthroat. Of greater interest to birders, however, are the tropical birds that reach their northernmost limit in or just north of the LRGV. Birders travel from all over the world to see these "Valley Specialties." Included in this group of special LRGV birds are: o Least Grebe o Muscovy Duck o Hook-billed Kite o Gray Hawk o White-tailed Hawk o Aplomado Falcon o Plain Chachalaca o Red-billed Pigeon o White-tipped Dove o Green Parakeet o Red-crowned Parrot o Groove-billed Ani o Ferruginous Pygmy-Owl o Pauraque o Buff-bellied Hummingbird o Ringed Kingfisher o Green Kingfisher o Northern Beardless-Tyrannulet o Brown-crested Flycatcher o Great Kiskadee o Tropical Kingbird o Couch’s Kingbird o Green Jay o Brown Jay o Tamaulipas Crow o Chihuahuan Raven o Cave Swallow o Clay-colored Robin o Long-billed Thrasher o Tropical Parula o White-collared Seedeater o Olive Sparrow o Botteri’s Sparrow o Altamira Oriole o Audubon’s Oriole In addition, many species from the tropics have wandered to the LRGV. Although not expected annually, these birds give credence to the notion that the LRGV functions as a major conjunction of tropical bird habitats and ranges. This list of rarities, many of which have only been recorded in the U.S. in the LRGV, includes: o Jabiru o White-cheeked Pintail o Masked Duck o Snail Kite o Crane Hawk o Roadside Hawk o Short-tailed Hawk o Collared Forest-Falcon o Northern Jacana o White-crowned Pigeon o Ruddy Ground-Dove o Ruddy Quail-Dove o Dark-billed Cuckoo o Mangrove Cuckoo o Mottled Owl o Stygian Owl o White-collared Swift o Green Violet-ear o Green-breasted Mango o White-eared Hummingbird o Elegant Trogon o Social Flycatcher o Sulphur-bellied Flycatcher o Fork-tailed Flycatcher o Rose-throated Becard o Masked Tityra o Yellow-green Vireo o Black-whiskered Vireo o Gray-breasted Martin o Orange-billed Nightingale-Thrush o White-throated Robin o Rufous-backed Robin o Black Catbird o Gray Silky-Flycatcher o "Mangrove" Yellow Warbler o Gray-crowned Yellowthroat o Golden-crowned Warbler o Rufous-capped Warbler o Yellow-faced Grassquit o Crimson-collared Grosbeak o Blue Bunting o "Fuertes" Orchard Oriole Because of its strategic location between tropic and temperate, the LRGV can truly be called the Crossroads of Migration for the Americas. The processions of migrant hawks, shorebirds, waterfowl and other waterbirds, hummingbirds, and songbirds, constitute one of the New World’s avian spectacles. On a single day, a birder can witness migrations involving tens of thousands of hawks, pelicans, and other birds. In addition to being one of the busiest migration pathways in the New World, the LRGV provides crucial stopover habitat for more than two hundred species of birds from Eastern and Western North America. These birds breed in tundra, northern forest, grasslands, subtropical scrub forest, and virtually all habitats north of the Mexican border. Without such stopover habitat, migration would be difficult, if not impossible for many species that need places to rest, feed, and avoid predators. Finally, the LRGV is the final migratory destination and wintering area for dozens of species of birds including world class aggregations of some waterfowl and other species. The combination of high species diversity, a large number of rare, threatened, and endangered species, large concentrations of wintering birds, several "endemic" subspecies, and a migratory pathway of hemispheric importance, makes the LRGV the most important bird area in North America. Mammals Eighty-three species of mammals are known from (or in the case of some marine mammals, expected to occur adjacent to) the LRGV's Willacy, Cameron, Hidalgo, and Starr counties. Another half dozen or so marine mammals including several large whales may occur well offshore in pelagic waters. If the Bottle-nosed Dolphin (frequently seen from land) is retained, and 13 other marine mammals that are rare or usually seen only well away from shore are ignored, the mammal list is left with 70 species. Jaguar and Pronghorn have been extirpated from the LRGV and six mammals were introduced, leaving 62 native species one might have a chance of encountering. These 62 species represent 34% of the 181 mammals known from Texas. Among the state’s mammals, ten are unique to the LRGV and another only occurs as well in the Big Bend vicinity. The unique mammals are Mexican Long-tongued Bat, Southern Yellow Bat, Texas Pocket Gopher, Gulf Coast Kangaroo Rat, Mexican Spiny Pocket Mouse, Coues’ Rice Rat, White-nosed Coati (also in Big Bend region), Eastern Hog-nosed Skunk, Ocelot, and Jaguarundi. Norway and Roof rats and the House Mouse were accidental Texas introductions that have caused significant damage to structures and foodstuffs, as well as spreading diseases. The South American Nutria was introduced as a furbearer, but has become a pest that ruins earthen dikes and competes elsewhere with the more valuable Muskrat. Feral Pig and Nilgai, both native to the Old World, were introduced as game animals. The former has become a damaging pest in some areas where it has decimated native flora and fauna, and has been the subject of expensive extermination campaigns. Nilgai is restricted to a number of ranches including properties in Willacy County where it is a curious and seemingly benign addition to the fauna. White-tailed Deer and Pronghorn are important game species; the latter has long been extirpated from the LRGV. Others such as the Black-tailed Jackrabbit and the two cottontails are of minor importance as game species; bobcats, coyotes, and birds of prey certainly take many more rabbits than do hunters. Sightings of native cats are rare and often rank among a naturalist’s lifetime highlights. Unlike East Africa, where a variety of cats may be observed during a short trip, the LRGV’s cats are rare and secretive. All of the LRGV’s cats have been persecuted as the subject of hunting pressure for sport, the commercial (and often illegal) hide market, and, in the case of Jaguar and Cougar, for being suspected predators of livestock. Jaguar (Federally Endangered) has been eliminated from South Texas; Cougar remains a rare resident, and the smaller Ocelot and Jaguarundi (both Federally Endangered) are restricted to dense brush lands along the coast and the relict woodlands bordering the Rio Grande. Only the Bobcat may be considered a locally common and widespread resident. Many of the remaining species are small, innocuous, and often nocturnal creatures that are rarely observed by humans. Of the ten species listed as unique to the LRGV, Southern Yellow Bat and Coues’ Rice Rat are listed as Threatened in Texas. In reality, any mammal species that depend on dwindling forest habitats along the Rio Grande is seriously threatened by habitat loss due to to farming and commercial development. |
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