How far is the whooping cranes' migration?
A. The distance between Aransas NWR in Texas and Wood Buffalo National
park in Canada's Northwest Territories is about 2,500 miles. Each spring
and fall the world's only natural flock of wild
migratory whooping cranes makes the annual journey between their wintering
grounds in Texas and their nesting grounds in northern Canada. The cranes
make the migration in about 2 to 3 weeks.
In 2001-01, a second wild flock of migratory whooping cranes was started
in Eastern North America with the help of ultralight airplanes. Cranes
lived here over a century ago, and are being reintroduced
once again. The new Eastern flock migrates between Wisconsin
and Florida, a distance of about 1,225 miles.
Q. When do whoopers leave their wintering grounds
A. The first whooping cranes in the Aransas/Wood Buffalo (or Western)
flock normally start the migration about mid-March. A few could leave
a little before that, but most of the population leaves during the first
half of April. Timing is similar for the whooping cranes in the reintroduced
Eastern flock, with wintering grounds in Florida.
Q. Why do cranes depart at almost the identical time
A. The departure schedule may vary by about a week from year to
year, but is remarkably consistent. Crane departures are based on hormonal
changes the birds are undergoing that are related to the longer days in
the spring. The length of day, or photoperiod, doesn't change from year
to year, and this is the key trigger to crane migration.
trigger simply makes the cranes ready to migrate. The actual take-off
happens on days when they get some help from the weather. Ideal migration
days have lots of sunlight. The sun beating on the ground makes some
areas a bit warmer than other areas: pavement is hotter than lawns,
land areas are warmer than lakes and streams. These differences in
temperature cause air over the warmer spots to rise, and that movement
of air (called a thermal) makes it much easier for cranes to stay aloft.
They can fly hundreds of miles in a single day with little work if
they get assistance from thermals and other favorable air currents.
They would never take off on a day with perfect migration conditions
in January or February. Until day length
is right, they won't start out, but once it is, they get to choose the days
on which they make their marathon flights.
Q. How do cranes prepare for the journey north?
A. Hormonal changes in the cranes allow them to gain weight
and build up the fat reserves necessary for the long migration. They
on blue crabs.
Q. When do the cranes arrive in their breeding (summer)
home in Canada?
A. They usually arrive in late April or early May, just as the
ice and snow are melting from the marshes. They have to get up to Wood
Buffalo National Park (60 N, -114 W) by early May in order to nest
time. The young chicks will need all summer to grow, learn to fly,
and gain endurance for the migration with their parents in fall. Timing
similar for the whoopers in the reintroduced Eastern flock, nesting
Q. What do the cranes do first upon arrival back in
Canada in the spring?
A. The cranes usually take a few days to check out the territory
they held last year before selecting a place to nest.
At what age (breeding age) do whooping cranes usually hatch their
cranes usually are 4 or 5 years old when they successfully hatch
their first young. Mating and nesting behaviors can appear in
cranes three or even two years of age. Inexperienced cranes
may not be successful at their first
nesting attempts. Parenting
Q. What is a whooping crane nest like?
Crane on Nest. Dalton Muir.
A. Their nests are built on small islands of bulrushes, cattails
and grassy wetland plants called sedges. There, the young are relatively
safe from predators. The marsh waters also provide food for whoopers.
One pair's nest, for example, was in about 25 centimeters of water. The
wetland where the pair nested was a mix of open water and sedge. The pair's
nest was constructed out of this sedge and was about 1 meter across.
Q. How many eggs do cranes normally lay?
A. Two eggs are normally laid by wild cranes. Usually only one
chick survives the summer and the migration to the wintering grounds in
Texas. Twins sometimes survive to make it, and you can read Tom Stehn's
report about the first
twins he saw. The first
eggs for the new Eastern flock were laid by two crane pairs in Wisconsin
in spring 2005, but the experienced adults accidentally wrecked the eggs
shortly after laying them.
Q. How long does it take for whooper eggs to hatch?
A. Both the male and female share incubation duties and they will
incubate the eggs for about 30 days before the eggs hatch. See An
Inside Story: Visualizing Inside the Egg.
Q. Why is the survival of young Whooping Crane chicks
greater during years with high water levels than during years with low
water levels in the breeding area?
A. In dry years the entire area is more accessible to land-based
predators; family groups have to travel over greater distances to find
food in the remaining wetlands and they may run into these predators.
Food supplies available to the cranes may also be limited, which adds
to the stress on the young while they are growing.
Q. When do young whoopers learn to fly?
A. The young birds fledge at about 9-10 weeks of age, or about
60-70 days of age. They are very vulnerable to predators before they can fly away from dangers.
Q. Do cranes mate for life?
A. Yes. They bond and nest together for life. However, it doesn't
always work that way. It is thought that "divorces" sometimes
occur among whooping cranes when a pair can't produce young that survive.
This is a survival instinct. For more, see Mates
Q. How fast do cranes fly during migration?
A. They can fly about 30 miles an hour. When pushed by strong
tailwinds, speeds of up to 60 mph have been recorded. With strong tailwinds, for
example, cranes of the main (Western) flock may have crossed nearly all of Texas
(over 400 miles) in one day. They make the migration from Texas to Canada
in 2-3 weeks. Cranes of the new eastern flock can migrate from Florida
to Wisconsin in a week. When Eastern flock crane colts are migrating with the aircraft, they can put on bursts of speed if needed, but their comfortable speed is between 35 and 38 mph. Once at cruising altitude after the climbing is done, the cranes and planes can sometimes make 40 mph or better.
Q. How far do cranes usually fly each day when they
A. They fly anywhere from 200-400 miles a day, often assisted
by thermals. As they fly, the whoopers of the western flock are spread
out in their north/south
corridor over 150 miles in width.
Q. Why is the timing of the cranes' migration so important?
A. The cranes have to balance the need to get to Canada by early
May in order to nest in time during the short summer season. But they
don't want to encounter severe spring blizzards on the way or have frozen
ponds when they reach the Northwest Territories in Canada at the end of
April or first week in May.
Q. Why do birds face into high winds, and take off
directly into headwinds?
A. Journey North students supplied good answers: They thought that
birds fly into the wind because if they go with the wind they'll have
no control of where they are going. Also the way feathers are shaped,
they would ruffle and may be damaged if the bird turned around. It is
more aerodynamic to fly into the wind.