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Whooping Crane

Whooping Crane Migration Update: April 9, 1998

Today's Update Includes:

Field Notes High Above Aransas

Tom Stehn

To: Journey North
From: Tom Stehn
Aransas National Wildlife Refuge
Austwell, Texas

And They're Off!
The whooping crane migration is in full swing. On April 2nd, I found only 139 cranes on my aerial census flight. This means an estimated 42 whoopers have started the spring migration!

About 23 cranes (five families and four pairs) started the migration sometime between March 26 and April 2. And then on April 5, Whooping Crane Tour Boat Captain Ted Appell watched 14 cranes start the migration from the south half of the Aransas refuge. Departures occurred between 9:50 and 10:30 AM, and included families, pairs, and subadults. The Mustang Lake/Nyarling family that refuge visitors see from the refuge observation tower also departed that day.

Cranes Head Home On South Winds
Even with so many cranes leaving within a short time period, these cranes have staggered starting times and leave in small groups of 2 or 3. Sometimes, two such units will join forces so possibly 5 cranes, or occasionally a few more, may be flying together. The departure of a territorial pair often "influences" its neighbors to leave shortly afterwards. All kinds of vocalizations are going on as the cranes depart. I wish I knew what they were saying. We might think they are saying the equivalent of "See you later. I'm off to Canada to nest", but in reality, the loud whoops are presumably more related to their territorial and dominance behaviors.

Cranes Head Home
South winds blew along the Texas Coast on April 5th, after this high pressure system moved to the east.

I'm anxious to do my next census flight on April 09 to see how many birds departed in early April. Probably I'll fly over parts of the whooping crane range and find most of the birds still present on their territories. Other sections of marsh will have only a few cranes left and feel very empty. This will demonstrate just how individualistic the whoopers are.

Migration Route
Map by Claudia Fonkert
Macalester College

That is probably very fortunate since what would happen if they all flew together in one big flock and encountered a blizzard, or tornadoes, or got up to the nesting grounds too early and couldn't find food in the ponds still covered with ice? The fact that whooping cranes have staggered departures helps the species survive. But all the adult birds have to get to Canada in time to nest since the northern summer is so short. Thus, the whooping cranes that depart one or two weeks later than most will make a more rapid migration north and will nearly catch up with some of the birds that left first.

Soon the telephone should be ringing with sighting reports of the whoopers as they make their 2,500-mile journey to the Northwest Territories of Canada.

Until next time,

Tom Stehn
Whooping Crane Biologist
Aransas National Wildlife Refuge
Austwell, Texas

Field Notes From The Great Plains

On the Lookout!
For years, Mr. Wally Jobman of the USFWS Ecological Services Unit has organized a network of observers across the Great Plains who report whooping crane migration sightings to him. Again this spring, he will forward these to you. At the same time, he'll provide a brief weather summary, describing the past week's weather patterns as they relate to whooping crane migration. Here is his first field report, sent from his home town of Grand Island, Nebraska along the famous Platte River:

To: Journey North
From: Wally Jobman

Greetings from the Cornhusker State! Typical spring weather last week, warm one day and cold the next. Up to 10 inches of snow in north-central Nebraska on Tuesday (3/31). The entire whooping crane flyway in the USA appeared to be pretty wet.

More recently, many sandhill cranes migrated from the Platte Valley, Nebraska, on April 4 and 6. Rain began during the evening of April 6, and continued through April 8 in Kansas, Nebraska, and South Dakota. Sunshine may return on Friday, April 10 and allow the migration to resume.

Thus far during the spring migration eight sightings have been confirmed as follows:

Wally Jobman
USFWS Ecological Services
Grand Island, Nebraska

Discussion of Challenge Question # 6
Last week, Tom Stehn reported on the continuing problem of crane deaths from power line collisions, and we challenged you to think of design changes to help make the power lines less harmful to wildlife. Making these design changes, however, can cause debate because they cost money and might cause power costs to increase.

As you read Tom's comments below, take a look at the "Cycling Through Controversy" Lesson, which is available in the Teacher's Manual at pp. 65 or click below.

But first, many thanks to Tim from Montana, who shared his suggestion based on the cranes he has seen flying in his family's rice fields. Tim said that "I have observed cranes landing in rice fields when fog was so thick the cranes could hardly see me but once they did see me they were quick to leave. I have also heard cranes flying at overhead at night. It has occured to me the cranes need sound as well as sight when flying in adverse weather conditions. Powerlines need to emit some type of chimes or clanging noise to alert the birds of the impending object in their flight path. Fog horns alert humans to dangers I'm sure there is some sort of noise the cranes would alert to. My name is Tim I work at Polson Middle School, Polson,Mt."
pmslib@cyberport.net (polson middle school library)

Thanks also to Tom Stehn, who tells us what steps and devices have been used so far to these prevent power line collisions. "The USFWS and Power/Utility companies have done a lot of research to address this issue of bird strikes and power lines. It is not just cranes - other birds can strike power lines and/or guy wires on tall radio communication towers, etc.

"The first step is not to allow new lines to be constructed near wetland areas where bird numbers are concentrated. Sometimes, based on environmental considerations, lines are re-routed to avoid areas of concern. Or perhaps a line can be placed underground to avoid the problem. I know at the Bosque del Apache National Wildlife Refuge, the two ultralight cranes had to make two flights a day over a low power line. The refuge has requested, and the power company agreed, to bury the line as soon as all the cranes leave in spring migration so that no hazard will exist next winter.

"If a line exists and can't be buried (after all, putting lines underground is much more costly than above ground), researchers have found that markers can be placed on the lines to make them more visibile to birds. You see this around airports where red balls are placed on the lines to allow pilots to see the lines. This same technique works well for birds and reduces collisions by 50%. Materials have also been wrapped around the line in a candy cane striped pattern, and metal rectangular plates have been hung from lines too, but the balls seem to work the best.

"Young first-year cranes seem more vulnerable to striking power lines compared to their parents. Perhaps that is because they are not as skilled a flyer when making a last-ditch effort to avoid a line they have seen too late, or perhaps they are not as skilled at recognizing lines, and probably just aren't paying as much attention to things around them.

"However, even if bird strikes are reduced by 50%, the continued construction of more utility lines in this country makes the bird strike problem grow every year. And that will continue as the human population continues to increase.

"Are you willing to pay a few cents more every month on your utility bill to ensure lines are marked properly? I would love every power line in the whooping crane corridor to be placed underground, but unfortunately this would be too costly and not practical since the migration corridor is about 150 miles wide by 2,500 miles long. Thus, power lines continue to be the number one source of mortality for whooping cranes."

"This is a good example of a human-caused factor that helps make and keep a bird endangered. After all, man-caused changes in the landscape that affect wildlife habitats are what cause species to become endangered. In very few cases are species these days going extinct becase of natural selection that is not influenced by man. We as people are the culprits, and thus we have a responsibility to save species that are endangered."

The Next Whooping Crane Migration Update Will be Posted on April 16, 1998.

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