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Whooping Crane Migration Update: March 18, 1999

Today's Report Includes:

Spring Comes to Texas
Spring is arriving in Texas, and Whooping Cranes are getting restless. But deep in their bones they know it's still late winter farther north. Biologist Tom Stehn reports from Aransas:

Monday, March 15, 1999
Dear Journey North:

This is the time of year when whooping cranes have to have a lot of patience. It's just too early to migrate. Right now it's beautiful here in Texas, with spring flowers blooming and trees leafing out. Last week, south winds up to 35 mph would have pushed any crane spreading its wings all the way across Texas to the Oklahoma border in one day of flying (430 miles). Yet Oklahoma just got hit by a blizzard, so the cranes have evolved to wait for longer days before they make a quick 2-3 week 2,500-mile journey to the Northwest Territories just south of the arctic circle.

My census flight on March 11 found only 172 whoopers, but I'm fairly sure nearly all 182 are still here. Showers limited visibility on the flight. I expect the cranes to start leaving in about two weeks.

Challenge Question # 2
"What is your prediction when the first Whooping Cranes will leave Aransas?" (Read Wally Jobman's report below and decide whether a couple of cranes might have sneaked out of Aransas before Tom's census.)

(To respond to this question, see below)

Spring Taking Its Time to Arrive in Nebraska
Wally Jobman at the U.S. Fish and Wildlife Service office in Grand Island, NE, sent us this note:

March 12, 1999
Dear Journey North:

Sandhill Cranes on a snowy NE corn field.

It appears, but is not yet verified, that we have two single whooping cranes in the Grand Island area. One bird is located about 3 miles west of Doniphan, and the other is about 2-3 miles south of Phillips, NE. We received several inches of snow on Monday (March 8) which makes it really difficult to locate the whooping cranes. No other whooping cranes have been confirmed in the flyway. The weather has been cold with snow cover this week, but forecast is for 50's and 60's next week. Hopefully, we will soon be able to verify whether there are one or two whooping cranes in the area."

Whooper or Pelican?
There are several kinds of big white birds that can be confused with Whooping Cranes. Sometimes birdwatchers mistake other species for whoopers. Tom Stehn explains the problem:

"Here at Aransas, we just had a visitor report seeing and filming a "mountain lion." When we checked his video, the animal was clearly the much more common bobcat. In a similar way, people sometimes see big white or light-colored birds and report them as whoopers."

Challenge Question # 3
Search through a field guide to find other birds that might be mistaken for Whooping Cranes on the ground. Also find at least two large white birds with black wingtips that could be mistaken for whoopers in flight. Also look at the ranges of these birds. Then answer

Challenge Question # 3: "If a group of students told Tom Stehn that they saw a whooper, what questions do you think he would ask them to be certain that they hadn't really seen another species?"

(To respond to this question, see below.)

Yes; No; Maybe So?

Tom explained the system the The U.S. Fish and Wildlife Service uses to judge sightings.

"We classify reports as confirmed, probably, or unconfirmed. A confirmed report is an observation from a qualified person (trained biologist, or very good birder) experienced in seeing whooping cranes. A probable sighting is when the description of the birds seems accurate, and data such as size of flock, time of year, and location, are all reasonable. An unconfirmed sighting is one which meets some but not all of the requirements for a probable sighting.

"For example, a report from California would not qualify since it is way too far west. When whooping cranes are reported on the ground (not just flying over), we try to get a trained biologist out to the site to confirm the report and determine if the whoopers face any hazards at that location (powerlines, diseases, hunting)."

Discussion of Challenge Question # 1
We asked:

  • How many chicks were produced this summer?
  • How many fledged?
  • How many young completed their fall migration?
  • What % mortality occurred of the young post-fledging? Was this average?
  • What percent of the adult/subadult population failed to arrive this winter? Was this average?

Seventh graders Antra, Merlin, Andrew, and Marvin at Iselin Middle School used the information provided to determine that of 48 chicks produced this summer, 24 fledged; 18 young completed their fall migration, so among the fledglings there was 25% mortality. This seems to be more than average because only 18 out of 24 survived. They decided that 20 young must live in order to keep the flock increasing. 9% of the adults/subadults failed to arrive and this is probably average since it is less than 10%.

How to Respond to Today's Challenge Question
1. Address an e-mail message to: jn-challenge-crane@learner.org
2. In the Subject Line of your message write: Challenge Question #2 (OR #3).
3. In the body of your message, answer the question.

The Next Whooping Crane Migration Update Will be Posted on April 1, 1999

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