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Tom Stehn |
Special thanks to Tom Stehn for providing his time and expertise in responding to your questions.
From: Texas
Valley Creek Elementary
dpalmer@mckinney.isd.tenet.edu
Q. Do whooping cranes migrate during the day or night?
A. Whooping cranes almost always are day-time migrants. They use thermal currents from daytime heating of the land to spiral as high as a mile in the air with very little flapping of their wings and then glide downwards in the proper direction until they "feel" the next thermal uprising of air. By taking advantage of the daytime, they avoid strenuous flapping flight and save energy during the long migration.
Q.Why do they migrate at this time?
A. The cranes have learned through hundreds and hundreds of years of trial and error (the ones that timed it right survived and raised young) that when the days reach a certain length, it is time for them to migrate north. If they leave too soon, they encounter ice and snow and won't find food when they reach the nesting grounds in Canada. If they leave too late, they won't be able to nest in time to raise young and get them big enough to make the fall migration in time.
Q. What altitude do the cranes fly at?
A. The cranes normally fly from between 1,000 and 5,000 feet high, all depending on the strength of thermal currents that allow them to get high. Late in the day, when the thermals are weak and stop altogether, the birds will try flapping flight at lower altitudes (I've seen them just 100 feet off the ground) but will soon get tired and look for a place to spend the night.
Q. At what age are females able to lay eggs?
A. Females are able to reproduce starting at age 3, though some approach 4 or even 5 before they lay eggs.
From: Minnesota
Pillsbury MST
tpierson@pillsbury.mpls.k12.mn.us
Q. Have you ever raised any whooping cranes yourself?
A. No. I've always worked with the wild flock of whooping cranes. I did help with the captive-raised whooping cranes that were led south behind the ultralight to New Mexico this fall. It was quite an experience to be able to stand next to these "tame" whoopers that were raised by people and thus not afraid.
Q. How do immature whooping cranes migrate?
A. The juvenile whoopers are taught the migration by their parents. Unlike other birds, cranes do not have instinct to show them the route. They usually spend the entire first year with their parents, making two migrations with them. They learn their lessons well since sometimes one-year-old cranes will migrate by themselves but have no trouble staying on the route they were shown. When I say "route", I mean a migration corridor about 150 miles wide. They are not following exactly the path they covered before. They have an amazing navigational ability to always know where they need to go.
Q. How fast do whooping cranes fly?
A. In straight flapping flight with no tailwinds, the birds can go 30 miles per hour. With strong tailwinds pushing them along, and gaining altitude on thermals and then gliding down, they reach speeds above 60 mph. The cranes, particularly in the fall, wait for strong tailwinds connected with storms that push south from Canada and aid the birds journey all the way to Texas.
From: British Columbia
Prince Rupert
sgregora@citytel.net
Q. What behaviors are learned and what ones innate?
A. In the process of introducing captive-reared cranes to the wild, we have learned a few interesting things about crane behavior.
(1) Cranes have an innate disposition to form pairs, defend territories, and build nests. In Florida, introduced whooping cranes have demonstrated all of these behaviors without any "instruction" by, or observation of, parent birds or other wild whooping cranes.
(2) Unlike some birds, crane migration is a learned rather than an innate behavior. The birds that have been introduced in Florida are the genetic relatives of whooping cranes that, historically, migrated between northern Canada and the Texas Gulf coast. The introduced Florida birds have not migrated during the normal migration period. They have remained in Florida as a year-round resident flock.
(3) Cranes show imprinting behavior very similar to the geese in Konrad Lorenz' classic imprinting studies. Whooping cranes raised from eggs by sandhill crane foster parents imprint on the foster parents. In fact, the whooping cranes that were raised that way, later would not breed with other whooping cranes because they had been sexually imprinted on sandhill cranes.
(4) Cranes' disposition for imprinting has been used to train sandhill and whooping cranes to migrate. First, the newly-hatched chicks are imprinted on a specific human. They will follow that person wherever he or she goes. When that person drives a land vehicle (truck or all-terrain-vehicle), the birds will follow. Later, after the birds can fly, they will follow that person if he or she pilots a small aircraft. This technique has been used to train several groups of cranes to migrate from a northern nesting location to a southern wintering location.
Tom Stehn
Whooping Crane Coordinator,
U.S.F.W.S.,
Aransas National Wildlife Refuge,
Austwell, Texas
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