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Answers From the Crane Expert

Special thanks to Journey North Science Writer, Laura Erickson, for providing her time and expertise in responding to your questions.


From: Oxford, Ohio

Q: I recently saw Whooping Cranes in Florida, quite unexpectedly. There were two feeding in a ditch near Florida's Turnpike south of Orlando, and another flying over a field in Everglades National Park. In both cases, I saw the bird before I knew what it was, and I wasn't expecting to see Whooping Cranes in Florida, but that's what they were. I had seen them on their winter grounds in Aransas National Wildlife Refuge in Texas, and I recognized the red crescent on their faces and in flight the black wingtips, like a White Ibis or a Snow Goose, but much larger. The size of the Whooping Crane is impressive, and I wonder if they are expanding their colony in Florida? I would like to think they are coming back from near extinction. Tell me more. Bill Pratt

A: This winter there were actually two different groups of reintroduced Whooping Cranes in Florida--the five that had followed an Ultralight down to Chassahowitzka National Wildlife Refuge as part of the WCEP (Whooping Crane Eastern Partnership) program to reintroduce wild migrating whoopers to eastern North America, and a group of over 90 Whooping Cranes that have been reintroduced as a non-migratory flock in the Kissimmee area. To find out more myself, I contacted Marty Folk, who works with the nonmigratory whoopers for the Florida Fish and Game Commission. He writes, "Yes, there have been a pair of whoopers near the Turnpike. They are 2 of our 90-some flock of whoopers. I am not aware of whoopers in the Everglades. However, some of our bird's transmitters have failed, making it impossible to track them." Marty tells us that "We currently have a pair of whoopers with a 5-week old chick and 3 other pairs on nests. We hope to fledge our first chick this year. We had a pair hatch 2 chicks in 2000 but they did not raise them up to fledging." As these cranes get older and more experienced, we sure hope they master reproduction so that the local population can grow and thrive. Having Whooping Cranes successfully breeding in Wood Buffalo National Park, the Kissimmee area of Florida, AND the Necedah National Wildlife Refuge in Wisconsin would be an enormous step in ensuring the long-term survival of this magnificent bird!


From: Clay Hill School
Hartford, Connecticut


Q: We noticed that whooping cranes eat blue crabs to prepare for their migration. What else do they especially like to eat, and what are the creatures further along the 'food chain', those that the blue crabs or their dinners might like?

A: According to Tom Stehn, blue crabs are the single most important part of the Whooping Cranes' winter diet-in a good winter, blue crabs make up 80-90% of a Whooping Crane's diet. These crabs have so much protein and other nutrients that they get Whooping Crane bodies in top condition for breeding. Whooping Cranes also eat some snakes, other crabs, an occasional fish, and some seeds, fruits, and tubers from plants.

Q: Is there anything affecting them that could be an influence on the cranes' own diet?

A: Blue crabs are considered scavengers and bottom feeders. They eat tiny marine plants, plankton, decaying organic matter, and animals called "macroinvertebrates" (insect larvae, leeches, worms, crabs, crayfish, shrimp, clams, oysters, mussels, and snails). They are also well-known for cannibalism--they mainly eat other blue crabs that are missing important appendages, filled with parasites, or in the process of molting. Cannibalized blue crabs can make up as much as 13% of a blue crab's diet! Besides Whooping Cranes and other crabs, blue crabs are eaten by a host of species: eels, carnivorous fish including sharks, sea turtles, egrets, herons, diving ducks, and raccoons. They're also eaten by humans.

One of the most important factors that affects blue crab survival is how salty the water is. Where there is too much "salinity," the crab population drops, and that is bad news for Whoopers! That is why Tom Stehn is so concerned about the amount of water being taken out of the Guadalupe and San Antonio Rivers. These two freshwater rivers pour into the estuary at Aransas, mixing with the salt water and keeping the salinity right for crabs. During droughts and when people remove too much water from the rivers, the salt levels in the estuary rise, and crab numbers fall. In those winters, more Whooping Cranes die, and the following summer, fewer Whooping Cranes successfully raise chicks.

Photo WCEP, Al Perry

Q: Some cranes seem to be more dominant than others. This is mentioned in a piece describing selection of the what individuals should carry transmitters. How do whooping cranes exhibit this dominance or subservience? Is it always the males who are dominant among cranes?

A: Birds have many similarities to us humans-probably because we share so much with them in our own biochemistry and anatomy. One way that cranes are similar to humans is that individuals have different behaviors and "personalities." (In the case of cranes, should we call them "crane-alities"?) In a healthy population of humans or cranes, some individuals tend to be more dominant, and others to be more submissive. Some dominant people are males, and some are females; the same is true of cranes. In cranes, because males are larger than females, the most dominant male is often dominant over the most dominant female, but a very dominant female is still dominant over most males.

Dominance and submissiveness are very important for keeping peace between cranes! If all the birds were equally dominant, the only way they could settle territorial arguments would be by fighting. Fortunately, since a flock of cranes develops a "pecking order," when a dominant one takes over a territory, the more submissive ones just move to other spots rather than fighting. There are plenty of good territories around for the relatively small number of cranes, so they solve most of their disputes without fighting at all. Too bad people can't learn from them!

Q: The crane population is very small and it is being expanded with eggs from only a few parents. Is there a risk of 'inbreeding' with the whooping cranes? We mean could some weaknesses or deficiencies come up in the cranes' bodies because they are too closely related?

A: What a great, insightful question! Yes, indeed, "inbreeding" is a major concern for people working to save the cranes. It's also one important reason why people should intervene to help endangered species while there are still a lot of individuals remaining.

Q: How can we prevent it or help them with this?

A: The Whooping Crane population went from a low of 15 wild migratory individuals and six non-migratory Louisiana birds in 1941 to almost 400 wild and captive birds in 2002. The Louisiana flock became extinct after a storm in 1950. Because the population was so tiny, scientists have been worried from the start about in-breeding, in wild as well as captive birds, and have worked hard to match up mates from unrelated birds. The birds that have provided the basis for captive breeding programs came originally from zoo birds from the early 1900s, and from eggs taken from wild nests in Wood Buffalo National Park in later decades. When people collect these eggs for the captive program, they take one of the two eggs per nest. This increases the chance that the remaining egg will hatch and the chick will survive, and gives scientists as wide a variety of individuals as possible, making the gene pool of the captive birds as diverse as possible.

The fact that Whooping Cranes are more fragile than Sandhill Cranes may, in part, be due to some in-breeding in the wild as well as the captive populations, but overall it appears that the precautions people have taken have given us a current population that is as genetically diverse as possible.

Laura Erickson
  • Click here to learn more about Laura, the wonderful books she's written, and much more information "For the Birds".


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