Especies destacadas: el gorrión saltamontes de Florida

El gorrión saltamontes de Florida (Ammodramus savannarum floridanus) is a nonmigratory subspecies of the grassland sparrow and is found only on the dry prairies of south-central Florida. The song of the Florida grasshopper sparrow sounds much like a grasshopper, which is where it gets its name. Males only sing a few hours a day during the breeding season to attract a female, and they often perch on grass stalks or dead palmetto fronds. Their song changes once they mate and begin building a nest, which helps scientists find their well-hidden nurseries.

The sparrow requires large treeless spaces dominated by bunch grasses, low shrubs, and saw palmetto with enough interspersed bare ground for this ground-dwelling bird to forage effectively. This habitat is dependent on frequent burning – so frequent, in fact, that sparrows very rarely nest on land that hasn’t burned within the last two years.  The sparrows also prefer areas where palmettos density is low or where they have been mechanically disked to allow more grasses to dominate.

Around 40 nesting pairs remain in the wild, making the Florida grasshopper sparrow North America’s most endangered bird. Habitat fragmentation and loss due to development, lack of frequent prairie fires, storm-related flooding, and high nest predation rates have caused a dramatic decline in its population over the past 40 years.

Ground-nesting birds like the Florida grasshopper sparrow suffer high nest failure but are able to re-nest several times a year in response. They are responding well to a captive breeding program established by the U. S. Fish and Wildlife Service (USFWS) at nonprofit White Oak Conservation in Yulee, FL, which the Foundation, the Florida Fish and Wildlife Conservation Commission (FWC), White Oak, and others are helping fund. Each nesting pair at White Oak is producing an astounding average of nine fledglings/year. The first of these captive-reared sparrows began being released back into the wild in May 2019, in hope of stabilizing and growing the largest-remaining wild population of the birds. More than 300 birds have been released since 2019, with releases ongoing. As of June 2021, biologists have detected at least 60 released birds in the population, including both males and females. 65% of the birds hatched in the wild in 2020 had at least one captive-bred and released parent. Biologists are still collecting data for the 2021 breeding season, but numbers are expected to be similar to 2020.

FWC and USFWS scientists have developed predator-exclusion fencing to reduce loss of eggs and young birds to snakes, skunks, raccoons, and other predators. Fire ants are a growing problem; scientists are on perpetual look-out for their nests, which are treated with boiling water to kill the worker ants before digging up the nest to kill the queen.

Durante los eventos de fuertes lluvias, el agua se acumula en la pradera. FWC y otros científicos levantarán cada nido varias pulgadas para salvarlo. Si se producen pocos nidos exitosos en una temporada determinada, puede tener resultados dramáticos en la disminución de la población.

¿POR QUÉ DEBEMOS CUIDARNOS SI DESAPARECEN ESTAS SPARROWS?

Salvar al gorrión saltamontes de Florida de la extinción es un trabajo intensivo en mano de obra, pero el gorrión lo vale. Es emblemático de las praderas secas de Florida, y su presencia o ausencia es un indicador confiable de la salud de todo el ecosistema.

Los gorriones de saltamontes de Florida también son intrínsecamente importantes como parte de la biodiversidad de Florida y América del Norte. La pérdida de una especie, como dice un científico, es como quemar un libro antes de leerlo. Una vez que se ha ido, nunca se puede recuperar.

Eso sucedió por última vez hace treinta años, cuando Florida y el mundo fueron testigos de la extinción del gorrión marino oscuro. Los esfuerzos de último minuto para salvar al ave a través de la cría en cautiverio llegaron demasiado tarde ya que las seis aves restantes eran machos.

¿CÓMO PUEDO AYUDAR?

Puede obtener más información sobre el gorrión de los pastizales de Florida y lo que se está haciendo para salvarlo a continuación. Deje que otros lo sepan y considere donando a nuestro fondo de conservación de gorriones.

MÁS SOBRE AHORRAR EL SPARROW DE FLASSIDA GRASSHOPPER

En junio de 1987, un pequeño pájaro blanco y negro con una franja amarilla distintiva sobre su ojo fue encontrado muerto en su plato de comida en el centro de especies en peligro de extinción en Walt Disney World, Florida. Llamado así por el identificador de metal en su pierna, Orange fue el último gorrión oscuro del mundo. Había sido capturado en 1980 con otros cinco, el último de un rebaño que alguna vez llegó a miles. Pero los biólogos actuaron demasiado tarde: Orange y sus compañeros eran todos hombres. Cuando la humanidad actuó, todas las hembras conocidas se habían ido.

América del Norte se enfrenta a otra extinción aviar. En las últimas praderas secas del centro-sur de Florida vive el ave más amenazada del continente, el gorrión saltamontes de Florida, Ammodramus savannarum floridanus. Threatened by predators, and since the 1970’s, significant habitat degradation and loss, fewer than 100 Florida grasshopper sparrows remain in the wild.

This is a race against extinction’s clock, a race this time we can win. The nonprofit Fish & Wildlife Foundation of Florida (FWFF), founded in 1994, is helping fund the work of scientists with White Oak Conservation, the Florida Fish and Wildlife Conservation Commission (FWC), and other organizations to save the sparrow. We have contributed $1,869,130 toward the best hope for sparrow survival – conservación (cautivo) cría y liberación. 

Conservation breeding is central to a five-year strategy to stabilize the sparrow’s wild population. Raising and releasing captive-bred birds also buys time to protect and restore more habitat, establish new wild populations, and better manage predators, parasites, and diseases that the birds are susceptible to. While our long-term goal is to make captive breeding unnecessary, without captive rearing now, models indicate the species will go extinct in the wild within ten years.

Unlike for many rare species, however, captive rearing of Florida grasshopper sparrows has proven a great success over its first four years.  The sparrows are prolific breeders, an adaptation common among ground-nesting birds whose eggs and young even in the best of times suffer significant predation and occasional flooding. For such birds, safety is in numbers – the more birds on the landscape, the greater the odds of individual nests and young birds escaping notice by small mammals and snakes. By rearing birds in captivity, safe from predators and other dangers, then releasing them into the wild, biologists can greatly increase the odds that juvenile birds will reach breeding age.

Most of the conservation rearing is being done at 700-acre White Oak Conservation, Inc., in Yulee FL, near Jacksonville. Part of the 17,000-acre White Oak Plantation, nonprofit White Oak Conservation is a pioneer in the breeding and recovery of many species. At a hatch weight of one ounce, the Florida grasshopper sparrow is the smallest species White Oak has taken on.

Since entering the program in 2016, White Oak has perfected techniques for breeding, hatching, and rearing sparrows, and currently has the capacity to care for 14 breeding pairs. Each of these pairs in 2017 successfully fledged a staggering average of 9.3 juveniles per breeding season. Extreme care is taken to keep captive birds free of extra-intestinal coccidiosis, eastern equine encephalitis, and other avian diseases.

Preparación para el lanzamiento: Fifty miles south of Orlando, within the country’s second-largest expanse of dry prairie, biologists have erected a temporary aviary to acclimate captive-reared birds before release into the wild. The first captive-reared birds were released into the largest remaining wild population in 2019.

FWC biologists are tracking them and are using special fencing and other strategies to keep skunks, snakes, raccoons, and other predators from attacking nests. More than 300 birds have been released into the wild in the last three years, starting with the first releases in 2019. In songbirds, such as Florida grasshopper sparrows, juvenile survival is naturally low. Therefore, many of the released birds do not survive to the next year and many individuals need to be released to have a significant positive impact on the population.

Nosotros y nuestros socios estamos recaudando o contribuyendo $1.7 millones to support the full grasshopper sparrow program. This includes the captive breeding and release program (including $300,000 to expand the captive population); protection of the remaining wild nests; and continued research on avian disease, predator control, and other needs.

Los programas de cría de conservación en cautiverio salvaron al cóndor de California y también pueden salvar a su pequeño primo de Florida. En los últimos años, los biólogos han aprendido cómo proteger y criar gorriones de saltamontes de Florida mientras mantienen o restauran su hábitat seco de pradera, una cantidad suficiente de la cual es propiedad de la conservación para mantener la existencia continua del ave. Tenemos la tierra, los expertos y, cada vez más, el conocimiento y la tecnología para recuperar esta especie. Estamos seguros de que podemos traer al gorrión saltamontes de Florida desde el borde, y nunca tener que mirar impotente mientras un futuro Orange envejece y muere junto con toda la esperanza de su especie.