Referat - Endangered Species

Categorie
Referate Biologie
Data adaugarii
acum 11 ani
Afisari
1111
Etichete
endangered, species
Descarcari
782
Nota
9 / 10 - 1 vot

Endangered Species
American Peregrine Falcon
In 1988, at a site now inundated by Greers Ferry Lake, peregrine falcons reared their young. Over a century passed before fledgling peregrines returned to Arkansas.
In June 1993, an environmental team flew to Minnesota and picked up five fledgling falcons. These birds were given a new home at the Arkansas Power & Light Company power station on the White River in Independence County. They were acclimated to their new area in a hacking station 300 feet above the ground, then released when ready to fly. Three birds survived and were often seen flying near the White and Black rivers.
In 1994, six more Minnesota peregrines were released from a hacking station atop the TCBY Tower in Little Rock, Arkansas's tallest building. It is hoped the relocated falcons will imprint on their new homeland and return to nest on permanent structures built for their use. Reintroductions like these have worked successfully in many other parts of the U.S., thanks in part to falconers who have raised thousands of peregrines in captivity for eventual release.
Although peregrines live on every continent except Antarctica, they are always rare. In Arkansas, they're most likely to be seen from mid-September through mid-May in southern lowlands.
The peregrine's recent history holds a cautionary tale. In the 1950s and '60s, these magnificent birds were nearly wiped out when their food chain was contaminated with pesticides, primarily DDT. All 275 known nesting sites in the eastern U. S. were deserted by 1964. To our good fortune, however, they were saved from extinction. There are now more than 1,200 pairs in North America, a four-fold increase in the last 20 years.
Unfortunately, we still have not roused ourselves to face the real enemy. DDT and other persistent pesticides continue to be manufactured and exported to the Third World, and the chemicals currently used in Western countries may be almost as deadly. Many contend we must change agricultural practices on a global scale; only then will we be heeding the message of hope the falcon brings.
Bald Eagle
In 1994, America's efforts to save endangered species reached a milestone with the announcement by the U. S. Fish and Wildlife Service that the bald eagle had recovered sufficiently to change its status from endangered to threatened in most of the nation. Bald eagle numbers in the lower 48 states climbed from 417 nesting pairs in 1963 to more than 4,400 pairs in 1994. In addition, 5,000 to 6,000 juvenile bald eagles live in the lower 48. Federal protection and tremendous public support led to this recovery -- through stricter law enforcement, protection of important habitat, reintroduction, a strong public education program and banning of DDT, a pesticide that interfered with normal eggshell production.
The first successful bald eagle nesting since 1930 was reported in Arkansas in 1982. In 1995, 18 pairs of Arkansas eagles successfully fledged young from the nest. An eagle hacking program started by the Game and Fish Commission in 1982 contributed to this resurgence. Young eagles from Minnesota and Wisconsin are brought to the state, raised in "hacking" facilities and released in hopes they will return to raise their young in Arkansas.
Arkansas ranks in the top 10 states in the number of winter bald eagle sightings. Over 1,000 bald eagles are counted each winter, nearly triple the 368 recorded in 1979.
Gray Bat
The gray bat's range is concentrated in the cave regions of Arkansas, Missouri, Kentucky, Tennessee and Alabama, with occasional colonies and individuals in adjacent states. The population is estimated at more than 1.5 million; however, about 95 percent hibernate in only eight caves -- two in Tennessee, three in Missouri, and one each in Kentucky, Alabama and Arkansas. This makes the population extremely vulnerable.
Gray bat numbers decreased significantly during recent decades -- 61 percent in Arkansas, 89 percent in Kentucky, 81 percent in Missouri and 76 percent in Tennessee and Alabama. The population is now on the upswing, though, as a result of improved breeding success due to better protection measures such as cave gates, fences and informational signs near caves.
One Arkansas hibernation cave houses about 250,000 gray bats, over 15 percent of the total population. About 150,000 gray bats occupy Arkansas caves in summer.
People who disturb hibernation and maternity colonies present one of the greatest threats. Maternity colonies won't tolerate any disturbance, especially when flightless newborn young are present. Thousands of baby bats may be dropped to their deaths or abandoned by panicked parents. If aroused during hibernation, bats increase use of stored fat reserves, and if the disturbance is intense or frequent enough, starvation may result before insects are available in spring.
Other factors ...


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