The Conservation of the Whooping Crane

"The quality of cranes lies...as yet beyond the reach of words" - Aldo Leopold

The majestic Whooping Crane in flight

The story of the Whooping Crane (Grus americana) is a legend in the making.  Scientists estimate that the Whooping Crane had a small population of between 10,000-20,000 individuals before the arrival of Europeans.  Habitat loss and hunting quickly took a toll on this relatively rare Gruiform, and by 1860 there were only about 1400 birds left in the wild.  By 1941, they were on the brink of extinction, with only 21 wild birds and 2 captives left.

Fortunately, the birds that were left spent both winters and summers in protected wildlife preserves; summers  in Wood Buffalo National park in Canada, and winters in Aransas National Wildlife Refuge in Texas.  Conservationists recognized the threat to the Whooping Crane and began agitating for governmental protection.  Governments and conservation organizations both at the summer and winter ground of the crane and the in-between stops began taking measures to protect the birds and encourage them to breed, and the species was eventually declared endangered.  Efforts to protect the crane saw a slow rise in numbers, to about 57 Whooping Cranes in 1970 and up to between 450-600 birds today.  While this bird has taken a few steps back from the abyss of oblivion, it still is critically endangered.

Scientists recognize that basing all conservation efforts on one population of Whooping Cranes is risky, and so they have taken bold steps to create other populations of the bird.  Captive breeding programs began increasing the numbers of these birds, but this presented a problem since none of the captives understood the methods and timing of migration.  Scientists tried to establish a population in Idaho, but it crashed.  They establishes a resident population in Florida as well, but this population does not migrate.  Crane researchers believed that they could adopt out Whooping Crane chicks to Sandhill Crane parents, who could teach the babies to migrate.  They did indeed teach them to migrate, but since the Whooping Cranes imprinted on the Sandhill Cranes, they would not breed with other Whooping Cranes.

A researcher dressed as an adult Whooping Crane to ensure the chick does not imprint on humans

A Whooping Crane chick being cared for by its parents

Then came a brilliant idea.  The International Whooping Crane Recovery Team suggested using an ultralight aircraft to teach the captive-bred chicks to migrate.  They established a population in Florida, and as summer approached, led up the ultralight, which the chicks had been flying around with locally, and flew to Wisconsin.  This effort proved successful, and there is now a second healthy population of Whooping Cranes that migrates annually between Florida and Wisconsin.  However, the majority of the individuals are still in the Aransas-Wood Buffalo population, and threats such as increasing habitat loss, illegal hunting, low genetic diversity, and natural disasters still menace this magnificent bird.  While the story of the Whooping Crane has been successful thus far, it will take generations of sustained effort to make sure that this species is  preserved in perpetuity.

Whooping Cranes following an ultralight

A scientist in the ultralight donning the crane suit to allow the chicks to believe that the ultralight is one of their own

Whooping Cranes flying in formation with the ultralight in the lead

Sources:

International Crane Foundation: http://www.savingcranes.org/whooping-crane.html
National Wildlife Foundation: http://www.nwf.org/Wildlife/Wildlife-Library/Birds/Whooping-Crane.aspx
US Fish and Wildlife Service: http://ecos.fws.gov/speciesProfile/profile/speciesProfile.action?spcode=B003

Gruiform Mating

To investigate the mating system of the Gruiformes, we will look at two species: The King Rail, in the family Rallidae, and the Sandhill Crane in the family Gruidae.

The Sandhill Crane

The King Rail

The Sandhill Crane, which is a much larger bird than the King Rail, has a slow life history.  They have been known to live over 20 years, and thus do not reach sexual maturity until between ages 3 and 5.  Some will find mates before they reach sexual maturity, but will not mate until maturity is reached. Sandhill cranes are monogamous and will generally only change partners in the case of the death of one partner.  The females select males based on plumage and call. During mating, they perform an elaborate dance ritual and engage in what is know as their unison call, where they call to one another during the dance routine.  Once copulation has occurred, both males and females will incubate the eggs for about a month.  The clutch size is, on average, 2 eggs/clutch for the Sandhill Crane.  The young are born precocial and leave the nest within 24 hours, usually one following one parent and one following the other.  Parents separate chicks because the more aggressive chick often will attack the more docile one.  The chicks fledge after 90 days and will remain with the parents until the following breeding season, which occurs one year later.

The mating dance of the Sandhill Crane

A typical clutch of 2 Sandhill Crane eggs, speckled for camouflage.

A precocial Sandhill Crane chick with an adult

The King Rail, in contrast, is a smaller bird with a shorter life history.  It only lives between 5 and 9 years, and thus much reach sexual maturity much earlier than its Gruidae cousin.  Mates are generally monogamous and philopatric from year to year.  The male attracts the female during mating by strutting and exposing white undertail coverts.  He also presents the female with gifts of food.  The male is also responsible for picking a next site and building the nest, in contrast with the more sharing nature of the Sandhill Crane in those duties.  After copulation, the female usually lays between 8 and 11 eggs, many more than the Sandhill Crane couple produced.  The eggsare incubated by both parents for between 21 and 23 days, and the young are born downy black and semi-precocial.  Despite this fact, they are also able to leave the nest after a day to follow their parents.  They fledge within about 2 months, which is a month sooner than the Sandhill Crane chicks, and by 7-9 weeks, the adults have stopped feeding and looking after the chicks, in contrast to the Sandhill Crane couple, which will provide some measure of care for about a year.

King Rails mating

A King Rail brooding a large clutch

A King Rail with three chicks in tow

Thus, with the King Rail and Sandhill Crane, we see two different life history types that lead to two different reproductive strategies.  The Sandhill Crane, with a slow life history, reaches sexual maturity at a late age and will raise only two chicks a year and care for them for the entire year.  In contrast, the King Rail, with a faster life history, reaches sexual maturity earlier, raises about ten chicks, and stops providing care after a couple of months.  The urgency displayed by the King Rail reflects the fewer opportunities that it has in its lifetime to breed as compared with the Sandhill Crane, which can have slow or no reproduction in some years but still have high lifetime fecundity.

Sources:

• Benedictine University Museum: http://www1.ben.edu/museum/kingrail.asp
• International Crane Foundation: http://www.savingcranes.org/sandhill-crane.html
• Michigan State University Extension: http://mnfi.anr.msu.edu/abstracts/zoology/Rallus_elegans.pdf
• National Wildlife Federation: http://www.nwf.org/Wildlife/Wildlife-Library/Birds/Sandhill-Crane.aspx
• Nebraska Game and Parks Division: http://outdoornebraska.ne.gov/wildlife/guides/migration/sandhill.asp
• Ohio Division of Wildlife: http://ohiodnr.com/Portals/9/pdf/pub382.pdf

Gruiform Morphology

As you can see from the pictures in the first post, the Gruiformes are very diverse in the way they look.  Faiq posted a great question: how are the rails related to the cranes?  They look nothing alike.  According to Gill, the order Gruiformes has few unifying characteristics.  The Wikipedia site states that some of the birds in this order were placed here simply out of necessity to place them somewhere, and hence, the order lacks apomorphies (derived characters found only in that group that would tie them together evolutionarily).  However, this statement, while plausible, is uncited.   The following tree, from Harshman, shows current Gruiform phylogeny:



As far as common morphology, the the similarities are:

• No member of the order has a crop, a digestive organ that serves to store food for later consumption or regurgitation; however, many birds, such as owls, also do not have crops, so this is not necessarily an apomorphy that evolved strictly in the Gruiformes.  In fact, since, as Gill states, the order is old, it may be the primitive character (no crop). (Gill)
• Most of the Gruiformes share "certain skeletal and palatal features". (Gill)  Livezey exhaustively covers these minute and numerous similarities in a 1998 paper.
• Most of the birds in this order have an oil gland. (Gill)
• Most of the birds in this order have "pervious nostrils", which are nostrils that, lacking a septum, are basically "see-through". (Gill)
• The Limpkin, which is the only species in the family Aramidae, is a larger wading bird which is the most crane-like in habit of the non-cranes in the order.  Harshman has the Limpkin most-closely related to the Cranes in his phylogenetic tree (see above).

Sandhill Crane (above) and Limpkin (below)

A great example of pervious nostrils in a Vulture - NOTE: Vultures ARE NOT Gruiformes!

An illustration detailing the crop.  None of the Gruiformes have a crop.

The morphological differences, however abound in these birds.  Rails (family Rallidae), such as the Black Rail, Virginia Rail, and King Rail, look much different than the, the American Coot (also in the family Rallidae), which superficially resembles a duck, dives for aquatic plants, and has lobed toes for swimming.  Many rails are also flightless, while their Gruiform cousin, the Cranes, undertake agonizingly long migrations.  Cranes are also very tall, gracile birds, while the Rails are shorter and rounder, some being almost grouse-like in shape and size.

A Coot and a Rail together.  One would not immediately leap to the conclusion that these birds are both in the same family.

A Whooping Crane, which superficially resembles an ibis or a heron more than a Rail or a Coot.

The foot of the American Coot, lobed for swimming, sets it apart not just from the other Gruiformes, but also of the other birds in its family, Rallidae.

As one can imagine, the systematics for this order have been difficult to sort out.  Harshman states that the Gruiformes are not a "natural group", and thus, many bird family have been plucked out of this order recently and put into other orders.  The Plains Wanderer (Pedionomidae) and Buttonquail (Turnicidae) have been removed from Gruiformes and placed in Charadriiformes.  Also the Seriemas (Cariamidae), Bustards (Otididae), Mesites (Mesitornithidae), Kagu (Rhynochetidae), and Sunbittern (Eurypygidae) have recently been removed from Gruiformes.

The Barred Buttonquail, which may superficially resemble a rail, has been removed from the order recently.

Sources:

• Gill, F. 1994. Ornithology, pp 641-643. W.H. Freeman and Company, New York, NY.
• Harshman, J. Gruiform Phylogeny. http://tolweb.org/Gruiformes/26307. Retrieved June 12, 2012.
• Livezey, B. C. 1998. A phylogenetic analysis of the Gruiformes (Aves) based on morphological characters with an emphasis on the rails (Rallidae). The Royal Society 2077-2151.
• Livezey, B. C. and R. L. Zusi. 2007. Higher order phylogeny of modern birds (Therapoda, Aves: Neornithes) based on comparitive anatomy. II. Analysis and discussion. Zoological Journal of the Linnean Society 149:1-95. 
• Ramel, Gordon. Gruiformes. http://www.earthlife.net/birds/gruiformes.html. Retrieved June 12, 2012.
• Wikipedia. Gruiformes. http://en.wikipedia.org/wiki/Gruiformes. Retrieved June 12, 2012.

Gruiformes is the order of birds that houses the rails, coots, limpkin and cranes.  In fact, the very name of the order means "crane-like".  Gruiformes is comprised of three families, nine genera, and twelve species in Eastern North America. Gruiformes prefer marshy wetlands for habitat.

• Rails are shy, secretive birds in the family Rallidae which prefer running and swimming to flying.  Some have long beaks for foraging in shallow water, but some have shorter beaks which can be used for the same purpose.  Representative species include the Virginia Rail, Black Rail, and Sora.  
• The Purple Gallinule, Common Moorhen, and American Coot are in the Rail family but resemble ducks more than other rails, and like ducks, can often be found floating on ponds.  The Moorhen is an avid swimmer, the Coot dives for aquatic plants, and the Gallinule rarely swims at all.  
• The Limpkin is the only extant species in the family Aramidae, is most closely related to the cranes, and has a small range in North America, more or less confined to Florida.  It searches the edges of ponds and streams looking for mollusks.  It has a wild, almost frightening call.  
• Cranes, of the order Gruidae, are easily the largest and most gregarious birds in the order, often found in flocks, and known for epic migrations.  They have cacophonous mating and courtship displays, which involve jumping and dancing as well.  The two American species are the Sandhill Crane and the endangered Whooping Crane, with less than 600 individuals in the wild.

The secretive Black Rail

The King Rail after a successful bout of crustacean-hunting

The unmistakeable Purple Gallinule, superficially resembling a pied duck more than its Rail cousins

The Limpkin, whose eerie call haunts the Florida marshes which it inhabits

The endangered Whooping Crane in flight with unmistakeable black wingtips on gorgeous white wings