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Whooping Crane Migration Update: April 25, 2000

Today's Report Includes:

All Adults are Canada Bound!
Aransas National Wildlife Refuge
Austwell, Texas
April 20, 2000

Dear Journey North,
An aerial census of the Aransas National Wildlife Refuge and surrounding areas made April 20, 2000 located only 5 whooping cranes. An estimated 10 cranes have started the migration since the last flight on April 13, including the final two adult pairs. As expected, all adults have normally left the wintering grounds by April 20.

Present were 4 subadults and 1 juvenile, all on Aransas. The juvenile that had separated from its parents was closely associated with three subadults. One subadult was by itself across from Rattlesnake Island.

These remaining cranes are expected to leave sometime within the next two weeks. Obviously, they are in no hurry since they don't have to get to the nesting grounds to breed. Occasionally one or two whooping cranes will fail to migrate and spend the summer at Aransas. I hope none of the five cranes do this since I always worry that cranes failing to migrate are sick.

Tom Stehn
Whooping Crane Coordinator

And You Think YOU'RE Busy?

Photo Couresty Dalton Muir, CWS

Last week Tom Stehn told us that cranes that didn't leave Aransas by April 20 wouldn't make it to the nesting grounds in time. What's the rush? You'll understand when you hear what's in store when they arrive! Tom Stehn describes what the whoopers must accomplish:

"Whooping cranes are on a tight schedule when they leave Aransas. They have to fly 2,500 miles, build a nest, lay eggs, incubate the eggs for 30 days, raise chicks that need about 80 days to get big enough to fly, allow the chicks time to build up flight endurance, and then migrate by early October before the weather gets too bad. To remain on schedule, the cranes must leave Aransas by April 20th in order to complete the 2-3 week migration and be sitting on a nest by May 15th. Successful nests are all hatched by June 15.

"One thing that really helps the cranes are the long summer days in the far north. They have more time to find food to feed the young. Plus, northern nesting grounds are extremely productive because of the short summer season. Once whooping cranes leave the nesting grounds in the fall, their lives become less scheduled since basically all they have to do is find food."

In the meantime, where are the whooping cranes now? Wally Jobman reports on. . .

The Journey North: Cranes Overflying Nebraska?
"Since my last report," reports Wally, "all confirmed sightings have come from North Dakota. Looks like the birds are overflying Nebraska this spring. Weather during the past week bounced from one extreme to the other. For example, Grand Island had a high of 80 degrees on April 14 and a high of 32 degrees on April 15 with freezing rain. April 17 to the present was generally good migration weather, with warm temps and predominantly south wind.

Remember that thermals and strong southeast winds provide ideal migration conditions. The latest data together with Wally's comments above will give you some clues to explaining last week's CQ #21. How do your thoughts match with Wally's thoughts? See the discussion of CQ #21 at the end of today's report.

Nesting For New Families

Photo Courtesy Brian Johns, CWS

Cranes build new nests soon after they arrive at Wood Buffalo. Canadian biologist Brian Johns of the Canadian Wildlife Service told Journey North what the nests are like:

"The nests are built in water and are about 1 metre across. Some nests are built from the bottom of the pond up while others are floating. The top of the nest is usually about 10 cm above the surface of the water. Preferred locations are ones that contain suitable nesting material, such as bulrush, sedge or cattails in about 15-30 cm of water." Why do you suppose cranes build their nests this way?

Photo Courtesy of Brian Johns, CWS

We asked Brian if he anticipates any problems for the cranes when they arrive. He answered, "One difficulty that the cranes may encounter when they arrive is cold weather that has the ponds frozen. The cranes are usually found feeding at any time of the day. Food items that they use are insects (the dragonfly nymphs are usually available in from late May to July), small fish (stickleback and dace), snails, tadpoles, frogs, and seeds. Drought is a major problem. Survival of young chicks is greater in years with high water levels and poorer in years with low water conditions." That leads us to ask:

Challenge Question #23:
"Why would chicks be more likely to survive in years with high water levels than in drought years?"

(To respond to this question, please follow the instructions below.)

Try This!
Follow the weather in Canada to see if you can tell whether the cranes get a "good welcome" this year.

NOTE: There is not a reporting station in NE Alberta at Wood Buffalo where the nesting grounds are. The nearest is about 150 miles to the south. At each reporting station (yellow circle with arrow) the temperature is the number shown at "10 o'clock." (Note link to "legend" at top of archives.)

Response to Challenge Question #19
We asked: "If the nesting pairs leave Aransas on April 20, when will they reach the nesting grounds in Canada?" Students from Iselin Middle School 7A in New Jersey were on top of this question. We'll just have to wait to see how the cranes follow through!

Kati DiRaimondo, Jalpa Bhavsar, Jason Crandall, and Frank Tedesco figured, "The nesting pairs will reach the nesting grounds in Canada somewhere between May 18 and June 1." (iselin5@injersey.infi.net)

Andy Soto told us how he reasoned and calculated: "In the good weather it will take at least 7.5 days to migrate without stopping. That would mean they would arrive in Canada on May 5. In strong tail winds it would take 3.75 days without stopping. That would mean they would arrive in Canada on May 1. We figured that they needed to stop, rest, and, eat so we added at least 1 week. That means it would be between May 1and May 5 when they arrive." Good thinking! How does your answer check with what Tom Stehn told us above? (iselin5@injersey.infi.net)

Response to Challenge Question #21
We asked you to look at the data and think about: "What are some reasons why so few sightings of migrating whoopers have been confirmed this spring?"

Here's what Wally Jobman thinks: "The fact that I am receiving few sightings probably means the birds are migrating quickly with no extended stopovers." It appears that the whoopers are flying fast while the flying is good!

Recognizing Pairs: Response to Challenge Question #22

Brian Johns, CWS

Last week we asked, "How do you suppose the biologists recognize the mated pairs that return each year?" Brian Johns fills us in:

"The mated pairs are identified in two ways. From 1975 to 1988 young were banded with coloured leg bands. These bands are still visible on some of the adult birds and they can be identified. In addition the cranes each have a territory that they return to each year. New pairs seek out territories adjacent to older established pairs or sometimes they may move into a completely unoccupied marsh. The unbanded pairs are the hardest to keep track of, especially if they move around within their territory."

How to Respond to Today's Challenge Question:
Please answer ONLY ONE question in EACH e-mail message.

1. Address an e-mail message to: jn-challenge-crane@learner.org
2. In the Subject Line of your message write: Challenge Question #23.
3. In the body of EACH message, give your answer to ONE of the questions above.

The FINAL Crane Migration Update Will Be Posted on May 9, 2000.

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