Whooping crane

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Whooping crane
Grus americana Sasata.jpg
Scientific classification edit
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Gruiformes
Family: Gruidae
Genus: Grus
Species: G. americana
Binomial name
Grus americana
Grus americana map.svg
Distribution map of the whooping crane. blue: breeding, orange: wintering, green: year-round, grey: experimental year-round
Synonyms

Ardea americana Linnaeus, 1758

The whooping crane (Grus americana), the tallest North American bird, is an endangered crane species named for its whooping sound. Along with the sandhill crane, it is one of only two crane species found in North America. The whooping crane's lifespan is estimated to be 22 to 24 years in the wild. After being pushed to the brink of extinction by unregulated hunting and loss of habitat to just 21 wild and two captive whooping cranes by 1941, conservation efforts have led to a limited recovery.[2] The total number of cranes in the surviving migratory population, plus three reintroduced flocks and in captivity, now exceeds 800 birds.

Description[edit]

An adult whooping crane is white with a red crown and a long, dark, pointed bill. Immature whooping cranes are cinnamon brown. While in flight, their long necks are kept straight and their long dark legs trail behind. Adult whooping cranes' black wing tips are visible during flight.

Whooping crane in flight

The species can stand up to 1.5 meters (4.9 feet) and have a wingspan of 2.3 meters (7.5 feet). Males weigh on average 7.3 kg (16 lb), while females weigh 6.2 kg (14 lb) on average (Erickson, 1976).[3] The body length averages about 132 cm (52 in).[4] The standard linear measurements of the whooping cranes are a wing chord length of 53–63 cm (21–25 in), an exposed culmen length of 11.7–16 cm (4.6–6.3 in) and a tarsus of 26–31 cm (10–12 in).[5] The only other very large, long-legged white birds in North America are: the great egret, which is over a foot (30 cm) shorter and one-seventh the weight of this crane; the great white heron, which is a morph of the great blue heron in Florida; and the wood stork. All three other birds are at least 30% smaller than the whooping crane. Herons and storks are also quite different in structure from the crane.[6]

Their calls are loud and can carry several kilometers. They express "guard calls", apparently to warn their partner about any potential danger. The crane pair will jointly call rhythmically ("unison call") after waking in the early morning, after courtship and when defending their territory. The first unison call ever recorded in the wild was taken in the whooping cranes' wintering area of the Aransas National Wildlife Refuge during December 1999 and is documented here [7]

Habitat[edit]

Whooping cranes breed in marshes.

The muskeg of the taiga in Wood Buffalo National Park, Alberta, Canada, and the surrounding area was the last remnant of the former nesting habitat of the Whooping Crane Summer Range. However, with the recent Whooping Crane Eastern Partnership Reintroduction Project, whooping cranes nested naturally for the first time in 100 years in the Necedah National Wildlife Refuge in central Wisconsin, United States. They nest on the ground, usually on a raised area in a marsh. The female lays 1 or 2 eggs, usually in late-April to mid-May. The blotchy, olive-coloured eggs average 2½ inches in breadth and 4 inches in length (60 by 100 mm), and weigh about 6.7 ounces (190 g). The incubation period is 29–31 days. Both parents brood the young, although the female is more likely to directly tend to the young. Usually no more than one young bird survives in a season. The parents often feed the young for 6–8 months after birth and the terminus of the offspring-parent relationship occurs after about 1 year.[citation needed]

Breeding populations winter along the Gulf coast of Texas, United States, near Rockport on the Aransas National Wildlife Refuge and along Sunset Lake in Portland, Matagorda Island, Isla San Jose, and portions of the Lamar Peninsula and Welder Point, which is on the east side of San Antonio Bay.[8]

The Salt Plains National Wildlife Refuge in Oklahoma is a major migratory stopover for the crane population hosting over 75% of the species annually.[9][10]

Six whooping crane wintered on Granger Lake in Central TX in 2011/2012. The group was made up of two mated pairs and their single offspring. One adult bird flew ahead to Aransas National Wildlife Refuge early in the season, but returned again to rejoin its mate and offspring. Drought conditions in 2011 exposed much of the lake bed, creating ample feeding grounds for this small group of cranes.[citation needed]

The whooping crane is endangered mainly as a result of habitat loss, although whoopers are also still illegally shot despite this being subject to substantial financial penalties and possible prison time.[11][12][13]

At one time, the range for these birds extended throughout midwestern North America. In 1941, the wild population consisted of 21 birds. Conservation efforts have led to a population increase; as of July 2010 there were about 383 whooping cranes living in the wild, and another 152 living in captivity. The whooping crane is still one of the rarest birds in North America. The United States Fish and Wildlife Service estimated the population at 505 whooping cranes in 2017.[14]

Predators[edit]

At Calgary Zoo, Alberta

Their many potential nest and brood predators include American black bear, wolverine, gray wolf, mountain lion, red fox, Canada lynx, bald eagle, and common raven. Golden eagles have killed young whooping cranes and fledgings.[15] The bobcat has killed many whooping cranes in Florida and Texas.[6] In Florida, bobcats have caused the great majority of mortalities among whooping cranes, including several adults and the first chick documented to be born in the wild in 60 years.[16][17][18][19][20][21] Patuxent Wildlife Research Center scientists believe that this is due to an overpopulation of bobcats caused by the absence or decrease in larger predators (the endangered Florida panther and the extirpated red wolf) that formerly preyed on bobcats.[17] At least 12 bobcats have been trapped and relocated in an attempt to save the cranes.[22] American alligators have taken a few whooping cranes in Florida.[17]

Diet[edit]

These birds forage while walking in shallow water or in fields, sometimes probing with their bills. They are omnivorous and more inclined to animal material than most other cranes. In their Texas wintering grounds, this species feeds on various crustaceans, mollusks, fish (such as eel), small reptiles and aquatic plants. Potential foods of breeding birds in summer include frogs, small rodents, small birds, fish, aquatic insects, crayfish, clams, snails, aquatic tubers, and berries. Six studies from 1946 to 2005 have reported that blue crabs are a significant food source[23] for whooping cranes wintering at Aransas National Wildlife Refuge, constituting up to 90 percent of their energy intake in two winters; 1992–93 and 1993-94.

Waste grain, including wheat, barley, and corn, is an important food for migrating whooping cranes,[6] but whooping cranes don't swallow gizzard stones and digest grains less efficiently than sandhill cranes.

Individual recognition, territorial and partnership fidelity[edit]

In earlier years, whooping crane chicks had been caught and banded (in the breeding areas of Wood Buffalo National Park), which has delivered valuable insight into individual life history and behaviour of the cranes. This technique, however, has been abandoned due to imminent danger for the cranes and the people performing the catching and banding activities.

By recording guard and unison calls followed by frequency analysis of the recording, a "voiceprint" of the individual crane (and of pairs) can be generated and compared over time. This technique was developed by B. Wessling and applied in the wintering refuge in Aransas and also partially in the breeding grounds in Canada over 5 years.[24] It delivered interesting results, i.e. that besides a certain fraction of stable pairs with strong affinity to their territories, there is a big fraction of cranes who change partners and territories.[25] Only one of the exciting results was to identify the "Lobstick" male when he still had his band; he later lost his band and was recognized by frequency analysis of his voice and then was confirmed to be over 26 years old, and still productive.

Conservation efforts[edit]

In 1957, the whooping crane was featured on a U.S. postage stamp supporting wildlife conservation.

Although believed to be naturally rare, the whooping crane has suffered major population declines due to habitat destruction and over-hunting. The population went from an estimated 10,000+ birds before the settling of Europeans on the continent to 1,300-1,400 birds by 1870 to 15 adults by 1938 in a single migratory flock. About thirteen additional birds lived in a non-migratory population in Louisiana, but this was scattered by a 1940 hurricane, which killed half of them, while the survivors never again reproduced in the wild.[26][27]

In the early 1960s, Robert Porter Allen, an ornithologist with the National Audubon Society, appeared as a guest challenger on the network television show "To Tell The Truth", which gave the Conservation movement some opportunity to update the public on their efforts to save the whooping crane from extinction. His initial efforts focused on public education, particularly among farmers and hunters. Beginning in 1961, the Whooping Crane Conservation Association (WCCA), was established to improve the status of the whooping cranes. This non-profit organization functioned largely by influencing federal, state and provincial political decisions and educating the general public about the critical status of the bird. The whooping crane was declared endangered in 1967.

Allen had begun an effort at captive breeding with a female crane named 'Josephine', the sole survivor of the Louisiana population, injured and taken into captivity in 1940, and two successive injured birds from the migratory population, 'Pete' and 'Crip', at the Audubon Zoo and the Aransas refuge. Josephine and Crip produced the first whooping crane born in captivity in 1950, but this chick only lived four days, and though decades of further efforts produced more than 50 eggs before Josephine's death in 1965, only four chicks survived to adulthood and none of them bred.[26][28] At the same time, the wild population was not thriving. In spite of the efforts of conservationists, the aging wild population would gain only 10 birds in the first 25 years of monitoring, with entire years passing without a single new juvenile joining those that returned to the Texas wintering grounds. This led to a renewed tension between those who favored efforts to preserve the wild population and others seeing a captive breeding program as the only hope for whooping crane survival, even though it must depend on individuals withdrawn from the extremely-vulnerable wild population.[26]

Identification of the location of the summer breeding grounds of the whooping cranes at Wood Buffalo National Park in 1954 allowed more detailed study of their reproductive habits in the wild, and led to the observation that while many breeding pairs laid two eggs, both chicks would almost never survive to fledge. It was concluded that the removal of a single egg from a two-egg clutch should still leave a single hatchling most likely to survive, while providing an individual for captive breeding. Such removals in alternating years showed no decline in the reproductive success of the wild cranes. The withdrawn eggs were transferred to the Patuxent Wildlife Research Center in Maryland, where approaches for hatching and rearing crane chicks in captivity had been optimized using the more-numerous sandhill cranes.[26] Initial challenges getting the resultant birds to reproduce, even using artificial insemination approaches, would give impetus to the first, unsuccessful attempt at reintroduction, by swapping whooping crane eggs into the nests of the more numerous sandhill cranes as a way to establish a backup population.[26]

In 1976, with the wild population numbering only 60 birds and having increased at an average of only one bird per year over the past decades,[26] ornithologist George W. Archibald, co-founder of the International Crane Foundation in Baraboo, Wisconsin, began working with 'Tex', a female whooping crane hatched at the San Antonio Zoo in 1967 to Crip and his new mate, the wild-captured 'Rosie', to get her to lay a fertile egg through artificial insemination.[29][28] Archibald pioneered several techniques to rear cranes in captivity, including the use of crane costumes by human handlers. Archibald spent three years with Tex, acting as a male crane – walking, calling, dancing – to shift her into reproductive condition. As Archibald recounted the tale on The Tonight Show in 1982, he stunned the audience and host Johnny Carson with the sad end of the story – the death of Tex shortly after the hatching of her one and only chick, named 'Gee Whiz'.[30][31] Gee Whiz was successfully raised and mated with female whooping cranes. The techniques pioneered at Patuxent, the International Crane Foundation and a program at the Calgary Zoo would give rise to a robust multi-institutional captive breeding program that would supply the cranes used in several additional captive breeding and reintroduction programs. A single male crane, 'Canus', rescued in 1964 as an injured wild chick and taken to Patuxent in 1966, would by the time of his 2003 death be the sire, grandsire or great-grandsire of 186 captive-bred whooping cranes.[32] In 2017, the decision was made for the Patuxent Wildlife Research Center to end its 51-year effort to breed and train whooping cranes for release, due to changing priorities and in the face of budget cuts by the Trump administration. Their flock of 75 birds was moved in 2018 to join captive breeding programs at zoos or private foundations, including the Calgary Zoo, the International Crane Foundation, the Audubon Species Survival Center in Louisiana, and other sites in Florida, Nebraska, Oklahoma and Texas. This relocation is expected to negatively impact the reproductive success of the captive cranes, at least in the short term, and there are concerns over its impact on the reintroduction efforts for which the Patuxent program had been providing birds.[33][34]

Meanwhile the wild crane population began a steady increase, such that in 2007 the Canadian Wildlife Service counted 266 birds at Wood Buffalo National Park, with 73 mating pairs that produced 80 chicks, 39 of which completed the fall migration,[35] while a United States Fish and Wildlife Service count in early 2017 estimated that 505 whooping cranes, including 49 juveniles, had arrived at Aransas National Wildlife Refuge that season.[14] A March 2018 Fish and Wildlife Service report counted an additional 161 cranes in captivity at twelve different sites, and an estimated 177 in three reintroduced flocks,[27] putting the total current population at over 800.

The wild cranes winter in marshy areas along the Gulf Coast in and surrounding the Aransas National Wildlife Refuge. An environmental group, The Aransas Project, has sued the Texas Commission on Environmental Quality (TCEQ), maintaining that the agency violated the Endangered Species Act by failing to ensure adequate water supplies for the birds' range. The group attributes the deaths of nearly two dozen whooping cranes in the winter of 2008 and 2009 to inadequate flows from the San Antonio and Guadalupe rivers.[36] In March 2013 during continuing drought conditions, a federal court ordered TCEQ to develop a habitat protection plan for the crane and to cease issuing permits for waters from the San Antonio and Guadalupe rivers. A judge amended the ruling to allow TCEQ to continue issuing permits necessary to protect the public's health and safety. An appeals court eventually granted a stay in the order during the appeals process.[36][37] The Guadalupe-Blanco and San Antonio river authorities joined TCEQ in the lawsuit, warning that restricting the use of their waters would have serious effects on the cities of New Braunfels and San Marcos as well as major industrial users along the coast.[36] To address the potential of future crowding that may result from the increasing migratory population, in 2012 and following years, purchases of small plots of land and acquisition of conservation easements covering larger areas has led to the protection of tens of thousands of additional acres of potential coastal habitat near the Aransas reserve.[38][39][40][41] A large purchase of over 17,000 acres in 2014 was paid for with $35 million made available from the settlement over the Deepwater Horizon oil spill money and an additional $15 million raised by a Texas parks non-profit.[42]

Concerns have been raised over the effects of climate change on the migratory cycle of the surviving wild population. The cranes arrive on their nesting grounds in April and May to breed and begin their nesting. When young whooping cranes are ready to leave the nest, they depart in September and follow the migratory trail through Texas.[43]

Reintroduction[edit]

Several attempts have been made to establish other breeding populations outside of captivity.

  • The first project, carried out by the United States Fish and Wildlife Service and the Canadian Wildlife Service and initiated in 1975, involved cross-fostering second eggs from the wild population in the nests of sandhill cranes to establish a second self-sustaining flock using a flyway from Idaho across Utah to New Mexico. The 289 transplanted eggs resulted in 85 chicks that learned to migrate,[44] but the whooping cranes failed to mate with other whooping cranes due to imprinting on their sandhill foster parents. The project was discontinued in 1989,[45] and no members of this population survive.[46] The initiation of this effort and the problem of imprinting are explored in the 1976 documentary A Great White Bird.[26]
  • A second effort involved the establishment of a non-migratory population near Kissimmee, Florida by a cooperative effort led by the U.S. and Canadian Whooping Crane Recovery Team in 1993.[47] A total of 289 captive-bred birds provided by the International Crane Foundation were released in the wild between 1993 and 2004.[48] Though in 2003 the population had produced the first chick conceived in the wild to reintroduced cranes, a decision was made in 2005 to introduce no further birds into the population until problems with high mortality and poor reproductive success were resolved. All studies of the population were discontinued in 2012.[49] The population numbered about 50 adults and 4 chicks in October 2006[50] but has since dwindled to just 14 cranes in March 2018. The Fish and Wildlife Service has proposed a plan to relocate the few surviving Kissimmee cranes to join the newer Louisiana reintroduced non-migratory flock.[49][27]
Young whooping cranes destined for the Eastern Migratory Population of reintroduced birds completing their first migration, from Wisconsin to Florida, in January 2009, following an ultralight aircraft.
  • A third attempt has involved reintroducing the whooping crane to a new flyway established east of the Mississippi river, with its southern end just west of the Atlantic flyway. This project used isolation rearing of young whooping cranes and trained them to follow ultralight aircraft, a method of re-establishing migration routes pioneered by Bill Lishman and Joe Duff working with Canada geese.[51] The ultralight flights were managed by a non-profit organization, Operation Migration,[52] working with the larger Whooping Crane Eastern Partnership (WCEP), which oversees all aspects of the reintroduced Eastern Migratory Population. Subsequent to hatching, the Operation Migration cranes were taught to follow the ultralight, fledged over their future breeding territory in Wisconsin, and led by the aircraft on their first migration from Wisconsin to Florida. Having learned the migratory route, they then returned north on their own the following spring. With the growth of this reintroduced population, WCEP also began releasing captive-reared juvenile cranes directly into the flock to learn migratory behavior from their peers, in a process referred to as Direct Autumn Release (DAR).
This reintroduction began in fall 2001 and added birds to the population in subsequent years. Two whooping crane chicks were hatched in the wild from one nest in 2006, to parents that had been part of the first ultralight-led release in 2002, and one of these survived to successfully migrate with her parents to Florida. In early February, 2007, 17 yearlings in a group of 18 were killed by the 2007 Central Florida tornadoes, with the sole survivor dying in late April an unknown cause, possibly related to the storm trauma. Two of the four DAR whooper chicks from 2006 were also lost due to predation.[53][54][55] In spite of this, as of May, 2011, there were 105 surviving whooping cranes in the Eastern Migratory Population (EMP), including seventeen that had formed pairs, several of which are nesting and are incubating eggs.[56][57]
In December 2011, the Operation Migration escort of nine cranes was interrupted by the Federal Aviation Administration due to a regulation prohibiting paid pilots of ultralight aircraft. After a month with the cranes kept in a pen, the FAA finally granted a one-time exemption to allow completion of the migration.[58] In January 2016, citing the near-total failure of the hand-raised and guided birds to reproduce in the wild, the Fish and Wildlife Service made a decision to discontinue the ultralight program in favor of alternatives with reduced human interaction.[59] In June 2018, the size of this population was estimated at 102 birds.[60]
The flock has established a range centered on southwestern Louisiana but also including central and northeastern Louisiana, southeastern Arkansas and southeastern Oklahoma, and east Texas, with some flock members seen farther afield. None of the first released group survived to full maturity, but in the Spring of 2014 the second cohort of birds began to form pairs and nest, producing the population's first eggs, although since the parents were still juveniles these eggs were infertile.[67] The next year saw fertile eggs but none survived to hatching.[68] However, in April 2016 a pair of reintroduced cranes hatched two chicks, one of which survived to fledge, represented the first in the wild in Louisiana since 1939.[69] Starting in 2017, a novel strategy was introduced: eggs in the process of hatching, taken from captive birds, were swapped into Louisiana nests in place of infertile eggs, allowing the chicks to be raised by substitute crane parents in the wild.[70] In 2018, a combination of naturally-laid and substituted eggs added five wild-raised juveniles to the population, which all survivied to fledge.[71] As of August 2018, 125 birds had been released, with at least 65 surviving.[72]

A major hurdle with some of these reintroduced populations has been deaths to illegal hunting.[73] Over a period of two years, five of the approximately 100 whooping cranes in the Eastern Migratory Population were illegally shot and killed. One of the dead cranes was the female known as "First Mom". In 2006, she and her mate were the first eastern captive raised and released whoopers to successfully raise a chick to adulthood in the wild. This was a particular blow to that population because whoopers in the East do not yet have an established successful breeding situation. On March 30, 2011, Wade Bennett, 18, of Cayuga, Indiana and an unnamed juvenile pleaded guilty to killing First Mom. After killing the crane, the juvenile had posed holding up its body. Bennett and the juvenile were sentenced to a $1 fine, probation, and court fees of about $500, a penalty which was denounced by various conservation organizations as being too light. The prosecuting attorney has estimated that the cost of raising and introducing to the wild one whooping crane could be as much as $100,000.[74][75][76][77] Overall, the International Crane Foundation estimates that the nearly 20% of deaths among the reintroduced cranes in the Eastern Migratory Population are due to shootings.[73]

Illegal shootings have also been a significant source of mortality for the Louisiana population, which suffered the killing of two and likely three cranes in October 2011,[78][79] one in April 2013,[80][67] two in February 2014,[67][81] one in November 2014,[82][68] two in November 2015,[83] two in January[84] and another two in May 2016,[85][86] and one in July 2018.[72] Two juveniles were apprehended for the 2011 incident,[87] a Louisiana man was sentenced to 45 days imprisonment and a $2500 fine after pleading guilty to the killing in November 2014,[88] and a Texas man was fined $25,000 for the January 2016 shooting and barred from possessing firearms during a 5-year probation period, on subsequent violation of which he was given an 11-month custodial sentence.[84][89] Two Louisiana juveniles were cited in 2018 for the May 2016 incident,[90] and a Louisiana man was cited for the 2018 shooting.[72]

References[edit]

  • Natural History article by Paul Johnsgard (1982)
  • Whooping Crane (Grus americana) from Paul Johnsgard, Cranes of the World (1983)
  • "Whooping Crane(Grus americana)". Texas Parks and Wildlife Department. Retrieved December 9, 2006.
  • McNulty, Faith, The Wildlife Stories of Faith McNulty, Chap.6 "The Whooping Crane" (pages 121-309), Doubleday 1980 (Chap. 6 was originally published as a book of the same title by E.P. Dutton in 1966). Much of her account deals with the work of Robert Porter Allen.
  • Tesky, Julie L. (1993). "Grus americana". U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. Retrieved December 9, 2006.
  • "Whooping Crane: On a Lost Path". U.S. Fish and Wildlife Service, Alamosa/Monte Vista National Wildlife Refuge. Retrieved December 9, 2006.
  • "Whooping Crane Flock Status". Whooping Crane Conservation Association. Retrieved January 27, 2007.
  • "Whooping Crane". International Crane Foundation, Baraboo, Wisconsin. Retrieved December 9, 2006.

Footnotes[edit]

  1. ^ BirdLife International (2012). "Grus americana". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 26 November 2013.
  2. ^ "Quivara National Wildlife Refuge: Whooping Crane, Grus americana". U.S. Fish & Wildlife Service. Retrieved 6 January 2017.
  3. ^ "Whooping Crane (Grus americana)". Texas Parks and Wildlife Department. Retrieved 2007-12-20.
  4. ^ http://www.nebraskabirdlibrary.org/index.php/gruiformes/gruidae/whooping-crane.html
  5. ^ [1]
  6. ^ a b c "Whooping Crane - - Birds of North America Online". bna.birds.cornell.edu.
  7. ^ "Craneworld - Kraniche in Bild und Ton: Schreikraniche im Duett". www.craneworld.de.
  8. ^ Tesky, Julie (1993). "Grus americana". Fire Effects Information System. USDA Forest Service. Retrieved 2009-11-23.
  9. ^ "NPS NNL description of Salt Plains". National Park Service.
  10. ^ "Species Status and Fact Sheet: WHOOPING CRANE". U.S. Fish and Wildlife Service.
  11. ^ "Endangered whooping cranes shot dead" CNN, 12 January 2011
  12. ^ Shryock, John. "Endangered whooping crane shot to death in Ala". wsfa.com.
  13. ^ "Endangered whooping crane shot and killed" "Animal Planet", 14 December 2009 [2]
  14. ^ a b "Whooping Crane Survey Results: Winter 2017–2018" (PDF). U.S. Fish and Wildlife Service. Retrieved 2018-08-27.
  15. ^ "Whooping Crane - - Birds of North America Online". bna.birds.cornell.edu.
  16. ^ "Whooping crane chick becomes bobcat victim". deseretnews.com. 29 May 2000.
  17. ^ a b c http://whoopers.usgs.gov/report4.htm
  18. ^ http://www.bringbackthecranes.org/media/2001/nr-12-18-01.html
  19. ^ http://www.bringbackthecranes.org/media/2002/nr-1-23-02.html
  20. ^ "Bobcat's A Suspect After 4 Whooping Cranes Killed". orlandosentinel.com.
  21. ^ Long, Jeff (2001-12-20). "Whooping crane flock loses 2nd member". Chicago Tribune.
  22. ^ "Bobcats Thin Flock Of Endangered Whooping Cranes". orlandosentinel.com.
  23. ^ https://birdsnews.com/2013/whooping-crane-migration-heightens-endangered-species-charisma/#.UnpfSBBjLdk
  24. ^ "Craneworld - Resumés: 7.3 Resumé 2003: Acoustic individual monitoring over six years". www.craneworld.de.
  25. ^ http://www.craneworld.de/pdf/schreikraniche/wildepopulation/vortrag.pdf
  26. ^ a b c d e f g McKennirey, Michael (1976). "A Great White Bird". National Film Board/Office national du film, Canada.
  27. ^ a b c Draft Environmental Assessment: A Proposal to Translocate Whooping Cranes from a Discontinued Non-Essential Experimental Population (BEP) in Central Florida to an Ongoing NEP in Southwestern Louisiana (PDF) (Report). U. S. Fish and Wildlife Service. June 2017.
  28. ^ a b Whooping Crane Master Plan for 2007 (PDF) (Report). January 2007.
  29. ^ "Tex, the whooping crane who needed a little encouragement..." UPI. June 24, 1982. Retrieved 2 October 2017.
  30. ^ "George & Tex". YouTube - International Crane Foundation. Retrieved 2 October 2017.
  31. ^ "Man courts whooping crane for three years to save it from extinction". Tree Hugger. June 30, 2015. Retrieved 2 October 2017.
  32. ^ "CANUS – 186 whooping crane descendants". Whooping Crane Conservation Association. 2013-02-25. Retrieved 2018-08-27.
  33. ^ "A 50-year effort to raise endangered whooping cranes comes to an end". Washington Post. September 18, 2017. Retrieved 1 October 2017.
  34. ^ Dance, Scott (12 October 2018). "End of an era: 50-year-old whooping crane breeding program coming to a close at Maryland's Patuxent refuge". The Baltimore Sun. |access-date= requires |url= (help)
  35. ^ Unrau, Jason (2007-12-17). "Whooping cranes sighted in record numbers". Toronto: Canadian Press. Missing or empty |url= (help); |access-date= requires |url= (help)Archived at Wayback Machine
  36. ^ a b c Texas Water Report: Going Deeper for the Solution Texas Comptroller of Public Accounts. Retrieved February 10, 2014
  37. ^ Texas Is Ordered to Supply Water to Crane Habitat March 12, 2013 Wall Street Journal
  38. ^ "Texas acquires land for endangered cranes". Victoria Advocate. 2012-10-12. Retrieved 2018-08-28.
  39. ^ Stephens, Garry. "Easement Program Enhances and Restores Whooping crane Wintering Habitat". USDA Natural Resources Conservation Service: Texas. Retrieved 2018-08-28.
  40. ^ "Critical Whooping Crane Wintering Grounds Purchased". Whooping Crane Conservation Association. Spring 2012. Retrieved 2018-08-28.
  41. ^ Sikes, David (2016-12-08). "Whoopers expand territory along Mission River and delta". Corpus Christi Caller-Times. Retrieved 2018-08-28.
  42. ^ Satija, Neena (2014-08-21). "Texas Buys Conservation Land With Oil Spill Money". The Texas Tribune. Retrieved 2018-08-28.
  43. ^ Butler, Matthew J.; Metzger, Kristine L.; Harris, Grant M. (1 April 2017). "Are whooping cranes destined for extinction? Climate change imperils recruitment and population growth". Ecology and Evolution. 7 (8). doi:10.1002/ece3.2892/full.
  44. ^ "Whooping Cranes On a Lost Path". US Fish & Wildlife Service. 2011-02-22. Missing or empty |url= (help) Archived at Wayback Machine
  45. ^ "Whooping Crane". International Crane Foundation. Missing or empty |url= (help)Archived at Wayback Machine
  46. ^ a b "FAQ: Whooping Crane Reintroduction in Louisiana". Department of Wildlife and Fisheries, State of Louisiana.
  47. ^ "Current Whooping Crane Flock Status". Whooping Crane Conservation Association. Missing or empty |url= (help)Archived at Wayback Machine
  48. ^ Florida's Whooping Cranes, Florida Fish and Wildlife Conservation Commission, retrieved 11 June 2016
  49. ^ a b Behrendt, Barbara; Pittman, Craig (2018-03-08). "Whooping cranes didn't so well in Florida. Next stop: Louisiana". Tampa Bay Times. Retrieved 2018-08-27.
  50. ^ "Current Whooping Crane Flock Status". International Crane Foundation. Missing or empty |url= (help)Archived on Wayback Machine
  51. ^ "Florida Whooping Crane Non-Migratory Flock (Synopsis)". Whooping Crane Conservation Association.
  52. ^ Crane Migration Operation Migration.
  53. ^ Walker, Cameron (5 February 2007). "Rare Cranes Led on Migration Killed in Florida Storms, Only 1 Survives". National Geographic Society. Retrieved 21 October 2015.
  54. ^ "Single Whooping Crane survives Florida tornadoes". BirdLife International. 2007-06-02. Retrieved 2007-12-20.
  55. ^ "Field Journal". Operation Migration Inc. Retrieved 2007-12-20.
  56. ^ "Flock Status – 2011 May «  Whooping Crane Conservation Association". Whooping Crane Conservation Association.
  57. ^ Whooping Crane Eastern Partnership December 2010 Project Update (Report). Whooping Crane Eastern Partnership. December 2010. Retrieved 2011-05-09.
  58. ^ Whooping cranes are cleared for takeoff after getting FAA exemption - CNN January 10, 2012 - accessed July 8, 2013.
  59. ^ Tribune wire reports (2016-01-24). "Feds to end ultralight aircraft-led whooping crane migration". chicagotribune.com. Retrieved 2016-06-05.
  60. ^ "Eastern Migratory Population Update". Operation Migration. 2018-06-06. Retrieved 2018-08-27.
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