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Whooping Crane Migration Update: April 9, 2002

Today's Report Includes:

Anne Lacey of ICF (That's not a crane!)

Map WCEP

Get Ready! South Winds and Calling Cranes in Florida
The Florida Five are still at Chassahowitzka--but maybe not for long! We reached ICF project biologist Anne Lacey on her cell phone just before this report went out. Anne said, "I'm out at the blind watching the birds right now as we speak. They're out and about, soaring overhead -- and it's a beautiful sight! We've got strong winds today out of the east-southeast and the sun is shining. The birds have been staying together a lot lately whenever they fly out and about. We're very happy about this. They've been calling to each other when in the air too. Of course, they may do that other times, and we're just not out here to see or hear it--but it's NEAT!"

In the meantime, ultralight pilot Joe Duff, who helped lead the cranes to Florida last fall, has a good reminder: "Just as wild birds do, our birds learned the migration route on a one-way trip. They followed us south as they would follow their parents to the wintering grounds where they separate from them as they mature and become more independent. It is then up to us as surrogate parents to remain calm and patiently wait for their return."

So, stay tuned. We'll send you a news flash when satellite signals tell us the Florida whoopers are in the air!

Wind Watch
Do you think the Florida cranes are saying, "Let's get out of here"? The sunny skies and winds Anne described make good migration weather. Let's take a closer look:

After viewing the page above, how will you answer this?

Challenge Question #14:
"What caused the central Florida winds to shift to the southeast on April 7-8? At the same time, how did the barometer reading change?"

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

This Should Be the Week: Tom Stehn's Field Report

Wild Family at Aransas
Photo Heather Ray

crane_Stehn02

Tom Stehn and Survey Plane
Whooping cranes are moving! In Nebraska, USFWS biologist Wally Jobman reports that the single whooper seen earlier is still around, and two birds have been confirmed on the Middle Loup River in Custer County, Nebraska. The birds have been there since last Thursday, but just confirmed on April 8. Reporting from Aransas, Tom Stehn says his survey flight on April 10th "should be interesting because it is right about when most of the cranes will depart, a few days either side of April 10th. Maybe I'll catch them right in the mid-point of departure." Tom wrote:

Dear Journey North.
Despite incredibly strong winds on Saturday March 30, I found out from my latest count of the whooping cranes that only 16 had started the migration between March 28 and April 4. Any crane that departed Aransas on windy March 30 could have crossed nearly all of Texas in one day, probably covering 400+ miles and averaging 60 mph. So why didn't the cranes all migrate?

Even though the cranes don't have suitcases to pack, the answer is simply that the whooping cranes weren't quite ready to leave. As the days lengthen, hormones in the cranes are changing. Those hormones are an important part of migration and the upcoming breeding season. Through thousands of years of trial and error, the cranes have learned not to leave too early because the far north up where they are going near the Arctic circle is still frozen. So despite the excellent migration conditions March 30, only a handful of cranes departed Aransas.

So I'm still waiting for the majority of the whooping cranes to leave their winter home. I really expect to have fewer than 100 cranes here when I next try to count them on April 10. So far, an estimated 25 cranes have started the migration out of the wintering flock of 174 whooping cranes, leaving 147 still present at Aransas.

Natural Hazards: Tom Discusses Challenge Questions #10 and #11
Last time Tom got us thinking about these two questions:
"What do you think are some natural hazards that the cranes face?"
"What are some reasons why the cranes leave at different times instead of all together?"

The 174 Aransas whooping cranes don't all migrate together, and Jesse and Tello of Berry Elementary Environmental Science Magnet School in Houston thought "they couldn't notice the other cranes leaving, or they wanted to be alone." Whoopers, unlike their sandhill cranes, prefer to migrate alone, in pairs, or in small family groups. The cranes too young to breed aren't in as much a hurry to get back, set up territories, and lay eggs as the breeding pairs are. Tom Stehn also points out a very important fact: leaving at separate times in small groups protects the flock from all running into a natural hazard that could wipe them out.

What are some of the natural disasters that cranes could face? Jesse and Christian at Berry Elementary Environmental Science Magnet School in Houston mentioned spring storms, snow, blizzards, hail and thunderstorms. Students from Eagle School in Madison thought that turbulance while flying over mountains could hurt the birds, and also flying into very strong winds could push the cranes backwards or off track.

Tom Stehn adds this about natural dangers: "One for sure is spring blizzards. A few years ago, a spring blizzard on the Platte River in Nebraska killed hundreds of sandhill cranes. Some got buried in snow drifts, and some had their beaks frozen shut with ice so that they couldn't breathe. Another natural hazard is lightning. Fortunately, cranes encountering a storm will simply stand out in the open and wait until it passes. This is a lot safer than for cows that will hide under a tree during a storm, with the tree being the highest object around to attract lighting."

Disease is another natural hazard. "As thousands of birds migrate north," says Tom, "many of them use the same wetlands and diseases can be spread in the water. Fortunately, most of the water is still cold in the early spring and doesn't yet provide good growing conditions for disease. This is more of a problem for migrating birds in the fall."

Towering Troubles: Link to Lesson
"None of these natural hazards are as dangerous to whooping cranes as the man-made hazard of power lines," states Tom, confirming what Nathalie and Megan suggested from Eagle School in Madison. Says Tom, "Whooping cranes hit power lines every year and are killed. I just learned there are over 1/2 million miles of transmission lines in the United States. These are the biggest lines high in the air. I don't know if anyone has ever calculated the amount of distribution lines, which are equally hazardous to whooping cranes. Anybody want to volunteer to calculate that figure? Distribution lines are the small lines usually right next to roads that bring electricity into your house. Cranes simply don't see power lines, big or small (transmission or distribution), and collide with them in flight," explains Tom.

One student from Eagle School in Madison recalled, "In Journey South one crane blew into the power lines and it died." Indeed, one of the ultralight-led flock was killed last October when it likely collided with a power line. You can review that Journey South report here:

Back to power lines and the towers that carry them. The fact is, our TV and cell phone habits are contributing to the deaths of millions of migratory birds a year. And by 2003, the government says all television stations must be digital. That means hundreds more towers--some taller than the Empire State Building. What's being done to help cut down the tower kills, and how can YOU help protect not only cranes but all migratory birds at risk from these mid-air death traps? Find out here:

Florida Five are Fine: Correction of Newspaper Reports

Ultralight-led Cranes in Florida Photo Operation Migration

A March 31 news story mistakenly reported that one of the Florida Five had broken its upper beak. The injured young whooper was not one of the ultralight-led cranes, but a new bird being introduced into the nonmigratory flock of whoopers that now lives in central Florida. The new crane was being released into the flock when it hurt its beak though a mishap. The bird is recuperating at the Lowry Park Zoo near Tampa.

The Pressure Is On: Discussion of Challenge Question #12
Last time we asked, "What makes barometric pressure so important for crane migration? How might cranes know when the air pressure is rising or falling?"

High pressure systems are associated with clear or partly cloudy skies, when the sun produces thermal air currents. Thermals and strong southeast winds are perfect for migrating cranes; thermals hold them up high, and a good tailwind pushes them in the right direction, so the cranes can go long distances with a minimum of flapping. You can learn more here:

Cranes probably START to migrate when barometric pressure begins to fall because that's when winds start to come out of the south -- as a high pressure system is leaving and a low is approaching. Low pressure systems are associated with rain, which make it very difficult for cranes to fly long distances.

The Built-in Barometer: Link to Lesson
How do cranes know whether the barometric pressure is high or low? No one knows! Scientists have long observed that birds can sense barometric pressure. They know this from observing at least two things:
  • Many birds increase feeding as the pressure falls, before other shifts in the weather give obvious signs that a storm is coming.
  • Birds migrating at night tend to stay at pretty much the same altitude, which they probably maintain in the same way that airplane pilots do. Pilots watch the altimeter, an instrument that senses the steady drop in barometric pressure as the altitude increases.

Scientists have different theories about how birds sense changes in barometric pressure. The two most popular theories are that birds may sense changes in air pressure in their inner ear (the way our own ears "pop" when we make a sudden change in altitude) or in the air spaces and air sacs within their bones and body cavity. Watch how barometric pressure changes with the weather. How might air pressure help or hinder birds in flight? Explore more here:

Short Tail: Discussion of Challenge Question #13
We asked, "Why is it good for cranes to have short tails? Steve, a fifth grader from Eagle School in Madison, said: "I think that it is important to have a short tail so the birds can make themselves more aero-dynamic." Thanks, Steve! Indeed, tails are useful for quick aerial maneuvers, but cranes fly slowly and directly, or spiral upwards on thermals in wide circles. That means a long tail wouldn't be useful for a crane. A long tail might actually drag in water, making it difficult to take off fast if a predator suddenly appeared.

Hereís a fact sheet with labeled photo illustrating the tail and other adaptations features on a whooping crane's body. You'll also discover the role of the black wing feathers and how cranes get enough oxygen at high altitudes:

Crane Adaptations: Challenge Question #15
You learned that cranes fly on thermals, which occur only during the day when the sun shines, but there's another good reason why cranes don't fly at night. This week, we ask you to consider adaptations around this question:

Challenge Question #15:
"Why don't cranes fly at night?"

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

Reminder to Teachers: Are You Ready for Satellite Tracking?
Imagine! This 2002 journey north is the first time satellite data has been available for whooping cranes! With the northward migration of the young cranes in Florida, we're about to share in observations we never had access to before. If you haven't already done so, you may want to develop or review the mapping skills your students will need to track the migration. Here are some tips and background lessons to help you get ready for satellite tracking:

How to Respond to Today's Challenge Questions:

IMPORTANT: 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 #14 (OR #15).
3. In the body of EACH message, give your answer to ONE of the questions above.

The Next Crane Migration Update Will Be Posted on April 16, 2002.

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