Tom Stehn Reports from Aransas: April 2, 2002 Tom Stehn and Survey Plane Dear Journey North, The whooping crane migration is underway, but only by a little bit. On March 28, after eight hours in the census airplane swooping, diving, circling, turning, and doing everything but breakdancing, (and every once and a while flying in a straight line), I concluded that a total of nine whooping cranes have started the migration. One of the nine has been sitting on the Platte River in Nebraska since March 20th. The other eight are cranes in four adult pairs that are headed north to nest. These pairs probably headed north on March 24th when it was incredibly windy on the Texas coast that would have provided strong 25 mph tailwinds to aid the birds as they crossed Texas. With winds like that, the cranes could have flown 60 mph and crossed almost all of Texas, flying 400+ miles all in one day. The winds sure were a handful for me windsurfing on the bay that day. I was easily going 30 mph myself, the sail pulling me along just as the wings of the cranes act as a sail catching the wind and making their migration easier. Why have 9 cranes started the migration and the remaining 185 in the flock are still here eating blue crabs getting ready for the trip? The timing of the migration is always spread out starting in late March and going all the way through April and sometimes even into early May before the last whooping crane departs. With the flock migrating at different times in small groups of usually 1-5 cranes, no single natural hazard will devastate the population. What do you think are some of the natural hazards that the cranes face? How do the cranes know when to migrate? It has to do with the length of the days. The cranes have an internal clock and ability to know how long the days are. (They don't have a wrist watch to tell time, but did you know they do have a wrist -- a joint located out near the tip of the wing?) How animals can measure the length of daylight is a mystery, but I know cranes can do it because I know I have an internal clock myself. How else can you explain that I usually wake up just BEFORE the alarm clock goes off, telling me it's time to go to work. How can I possibly do this unless I have an internal clock that mysteriously wakes me up? So somehow the cranes use their internal clocks and know that the spring days are getting longer. This triggers hormonal changes in the cranes, readying them for the migration. They eat more, gain weight, and build up fat reserves needed for the long, hard migration. And when the days reach a certain length, off they go to Canada for the summer. I expect most of the whooping cranes will start the migration between April 5 and April 15. After about April 20th, all the breeding pairs have migrated. It is the younger non-breeding cranes that may stay another week or two after that since they do not have to get up to Canada to build a nest and lay eggs. Safe traveling to the nine whooping cranes that have started the migration. Tom Stehn Whooping Crane Coordinator U.S. Fish and Wildlife Service Try This! Journaling Question Why do you think the cranes' departure is spread out over such a long period of time? What do you think are some of the natural hazards that the cranes face? Copyright 2002 Journey North. All Rights Reserved. Please send all questions, comments, and suggestions to our feedback form