Whooping Crane Migration Update: April 3, 1997

Claudia Fonkert, Macalester College

"I did an aerial census flight on March 27, I still found 154 cranes at Aransas", said Tom Stehn. "One adult pair (and possibly 1 or 2 subadults) have started the migration. The rest are all still here eating blue crabs."

According to Stehn, strong southeast winds and thermals provide ideal migration conditions. Cranes usually depart when high pressure systems brings south or east winds and sunshine to Texas. All along their migration path, the whoopers wait for high pressure and favorable winds to continue their migration. In contrast, low pressure systems are associated with storms. (The winds whirl counterclockwise around the low pressure system.) The least favorable conditions for crane migration are low pressure systems with north winds. When the migrating whoopers encounter these storms with their north winds, the birds will quickly find a place to land and wait for several days until the north winds rotate back around to the south.

During these storms, the whoopers will make short daily flights out to grain fields to feed, returning to wetlands where they will spend the night. It is during these short low altitude flights where they might collide with power lines and be killed, especially during rain or snow storms when the power lines are not very visible.

During the month of April, whooping crane migration updates will be posted every Thursday, so you can follow their progress closely.

On the Lookout on the Great Plains
For years, Mr. Wally Jobman of the USFWS Ecological Services Unit has organized a network 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 provides a 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:

USFWS

"An adult-plumaged bird was first observed on March 9th and has been roosting on the Platte River south of Alda, NE. A juvenile was first observed on March 19, and has been roosting on the Platte River south of Gibbon, NE. The juvenile was apparently a bird which became separated from its parents during the fall migration and wintered in OK or TX with sandhill cranes. This bird doesn't know the way to Aransas NWR, but should be able to return to Wood Buffalo NP. The adult-plumaged bird may or may not have wintered at Aransas. I suspect that it did not.

"We should begin to get sightings of other migrants within the next few days."

To:	Journey North
From:	Tom Stehn, Aransas National Wildlife Refuge
Date:	March 31, 1997

"The exciting news from Aransas this week is that another whooping crane has been added to the population! Thanks to biologists in Nebraska, they confirmed a sighting of a juvenile whooping crane near the Platte River. It was first seen on March 9, as I mentioned to you in my March 11th update. On that same day, I counted the cranes at Aransas and found all 15 juveniles that I had been monitoring all winter still with their parents. So that proved that the juvenile in Nebraska had never been at Aransas.

"With the addition of this Nebraska whooper, the population currently alive is 143 adults + 16 juveniles = 159 whooping cranes.

"What probably happened is that this juvenile whooper in Nebraska got separated from its parents during the migration last fall. It continued to fly south, probably following its sandhill cousins. It wintered in an unknown location, probably somewhere in Texas or thousands of sandhills. I'm sure this whooper will make it back up to Wood Buffalo National Park in Canada this summer where it will find other whooping cranes. Maybe next fall it will follow one of the other whooping cranes and show up at Aransas.

"We know of several instances of juveniles separating from their parents in the fall migration. This happened to one color-banded juvenile in 1984 and it finally found its way to Aransas three years later, after it had found a mate who showed it where Aransas was. This bird established a territory and was successful in raising young and bringing them to Aransas. So hopefully the same kind of story will happen to the juvenile currently in Nebraska. Unfortunately, this bird is not color-banded so we won't know if it ever shows up at Aransas."

The Next Whooping Crane Migration Update Will be Posted on April 10, 1997