Wintering Whooping Crane Update: September 16, 2014
Wade Harrell, U.S. Whooping Crane Recovery Coordinator
We’ve had exciting news here at Aransas National Wildlife Refuge: four adult whooping cranes arrived about a month ahead of normal early arrival time! These four birds were first sighted on Friday, September 12 by an area fishing guide and confirmed with photos by Refuge staff on Monday, September 15. Although not unheard of, this early arrival is fairly rare. The average early arrival date for wintering whooping cranes is around the second week of October. We haven’t had any other migration reports as of yet, but as frontal passages become more frequent, migration should begin in earnest.
Fall Migration Behavior
I often receive questions about timing and speed of migration this time of the year, and will try to summarize what we know about whooping crane migration. We have some information that was collected by the Canadian Wildlife Service during the first whooping crane telemetry study in the early 1980’s. At that time, researchers actually followed a few migrating whooping cranes in a single-engine prop plane to determine migration behavior. Here is a bulleted summary of some of the findings:
(Kuyt, E. 1992. Aerial radio-tracking of whooping cranes migrating between Wood Buffalo National Park and Aransas National Wildlife Refuge, 1981-84.)
Whooping cranes do not all migrate simultaneously.
Total migration distance is 2,500 miles.
“Fall migration of yearlings and subadults began after the middle of September, with family groups and some paired adults following in early October.”
“Whooping cranes usually migrated as pairs, family groups or small aggregates of 4-5 subadults.”
Weather conditions were important in determining migration initiation and stopovers.
Typical fall migration took up to 50 days, consisting of a:
2-3 day flight from the breeding grounds Wood Buffalo NP to Saskatchewan;
1-5 week “staging period” in the Saskatchewan prairie pothole region; and a
1 week journey through the US plains states.
During average flying days, under normal weather conditions, flights consisted of:
Flights during daylight hours;
Average flight distance of 250 miles over 7.5 hrs; and
Flights at < 2,000 ft. altitude.
Greatest observed flight behaviors included:
Flight speed of >62 miles per hour;
Flight altitude of 6,400 ft.; and
Daily flight distance > 500 miles.
As the whooping crane population continues to grow, we expect to see a wider range of behaviors than we have observed in the past. Keep in mind when the study referenced above was conducted, there were only about 75 whooping cranes in the Aransas-Wood Buffalo population and now there are over 300. A larger population will exhibit a greater variation in behaviors, which will help the species continue to recover (i.e. individuals seeking out new habitats, etc.).