Whooping Crane Migration Update: May 1, 1997

USFWS

To: Journey North

From: Tom Stehn

Date: May 1, 1997

Dear Journey North,

All the breeding whooping cranes have headed north, and some should already be in Wood Buffalo National Park by now. I did a census flight at Aransas on April 24 and found only 13 cranes still here. They are all young birds that we call subadults (about like being in Junior High School for people).

Whooping cranes normally pair up and nest between ages 3 and 5, so subadults are generally less than 3 years old. They are in no hurry to leave Aransas and head north since they don't have a timetable to keep as far as building nests and raising young. Some of these subadults could stay at Aransas into May. Last year, one subadult didn't depart until June. And some years, a few cranes may decide to skip all that travel and spend the summer at Aransas. This arrangement makes a lot of sense, since the remaining cranes will find lots of blue crabs to eat all summer. But the migratory urge doesn't work that way. It is so strong that almost all the whooping cranes migrate even if they are not old enough to breed. I've scheduled my nest census flight May 6 to see if any of the whoopers are still here.

The big surprise on my flight April 24 was the presence of one juvenile whooping crane. Its parents had migrated on April 10th and left it behind. Observations of other juveniles being left indicate that this is not an aggressive move by the parents forcing the chick to separate. Instead, the parents have the migratory urge and the chick does not, and thus a separation occurs. The chick has to be saying "Where are you going" as the parents spiral up and out of sight.

I had apparently overlooked this juvenile crane when I flew April 17. It has just a little brown on the neck and head which is the only juvenal plumage remaining. In another few months, this bird will be completely white (with black wing tips) and look just like any adult. The plumage must have fooled me if I saw the bird on the 17th. This juvenile knows the way back to Wood Buffalo and probably will make the journey, though it certainly is a candidate for a crane that could possibly spend the summer at Aransas. We get a summering whooper about once every five years.

Now that all the breeding whoopers are on their way, many development activities in the crane areas are underway. These activites are not allowed during winter. They include oil and gas exploration (seismic surveys) and drilling, and dredging of the Gulf Intracoastal Waterway that carries barges and other boat traffic through the whooping crane area. Monitoring development and doing habitat management for the cranes and other wildlife at Aransas keeps me busy all summer. And in June, I'll be helping Canadian Whooping Crane Coordinator Brian Johns figure out how many chicks have hatched. Just never a slow time in the whooping crane year.

Tom Stehn
Refuge Biologist
Aransas NWR

To: Journey North

From: Wally Jobman

Date: May 1, 1997

Only four confirmed sightings were received at the Grand Island Field Office during the past week. I would estimate that about 90 percent of the whooping cranes are now north of Nebraska.

• Link to Today's Migration Data

Weather conditions were generally good during the past week. There were no major storms and winds were generally from an easterly or southerly direction. A storm system moved through Nebraska Tuesday night (4/29/97), and today we have a strong north wind. Unsettled weather is predicted for the next few days.

In response to your question about the number of reported sightings being down this spring as compared to previous years, I offer the following educated guess:

The birds were a little slow in initiating migration, and it appears that they traveled through the U.S. portion of the migration route very quickly. We had about an average number of sightings in Nebraska, but the Dakotas were down slightly. There is so much water in the Dakotas and many roosting sites are available. This compares to dry years when roosting habitat is very restricted. Having a variety of roosting sites may lower the probability that birds would be observed.

Wally Jobman
USFWS
Grand Island, NE

Expected Time Of Arrival?
We just heard from Canadian Wildlife Service Biologist Brian Johns who right now is on his way to the Whooping Crane nesting grounds in Wood Buffalo. Brian has promised to send us a report as soon as he returns, so we'll keep you posted on the whoopers' arrival!

The Next Whooping Crane Migration Update Will Be Posted On May 15, 1997