Whooping Crane Whooping Crane
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April 13, 2006

Dear Journey North,
The big push-off that I’ve been anticipating occurred right on schedule. Nearly half of the whooping crane flock left Aransas this past week, with an estimated 102 birds starting migration April 5-12. Some of the flock is already well on their way, with sightings received from as far north as North Dakota. The whooping cranes travel though Texas, Oklahoma, Kansas, Nebraska, South Dakota, North Dakota, and the easternmost portions of Montana. I bet some of you forgot to list Montana as a state the whooping cranes migrate through. Now name the 3 Canadian provinces the whooping
cranes have to fly across. Here is a hint – the easternmost of these 3
provinces only gets a few whooping crane sightings.

A Big Week For Migration
During April 5 - 12, an estimated 102 whooping cranes (47.7% of the flock)
eft Aransas. During that period, most days provided suitable weather for migration except when a low pressure system brought strong northwest winds to Aransas on April 8th. That front crossed the coast quickly, with groups of whooping cranes reported starting the migration on April 9 and 10 with the winds turning around and blowing from the southeast. Sunshine and warm temperatures in Texas currently in the 80’s heats up the land and creates thermal currents to aid the migration of birds with large wing spans such as cranes and pelicans, and hawks. Thermal currents come from the hot air rising due to temperature differences between the earth’s surface and the sky. Birds with smaller wings don’t have a large enough wing span to
“ride” thermal currents. Thus, small birds such as songbirds and shorebirds flap their wings at a rapid pace and fly in a straight line. I think I’d want to be a large bird and simply spread my wings and ride the thermal currents up a mile high in the sky and then glide down 4,000 feet at 60 miles per hour as I traveled north, catching the next thermal when I got down close to the ground. In the late afternoon when the thermals were dying out, I would look for a place to stop, eat a little bit, and spend
the night.

Only an estimated 35 whooping cranes (32 adults + 3 chicks) are currently still at Aransas. Thus, 83.6% of the flock has migrated. Remaining at Aransas are 2 family groups, 28 subadults, and 1 chick all by itself.

One Lone Chick?
Why do you think so many subadults are still at Aransas? Whooping crane juveniles normally separate from their parents either shortly after arrival on the nesting grounds, en route in the northern parts of the migration, or occasionally separate at Aransas. Presumably the parents started the migration and the juvenile had no idea what was going on or perhaps just wasn’t quite ready to migrate, so it stayed behind. Based on other instances of this happening, I fully expect this juvenile will head north in the next 2-4 weeks and successfully return to the Canadian nesting grounds. It will presumably even show up on its parent’s nesting territory, but will be driven off by the parents who will not tolerate last year’s chick.

Whooping cranes are usually quite vocal as they start a migration flight. Can anybody think about what the chick and its parents were saying to each other as the adults started migration and the chick stayed behind? I bet the chick was saying: “Where the heck are you off to? No way am I going to migrate 2,500 miles just to eat berries and insects!”

Crane Look-alikes
I also observed on my census flight that the numbers of white pelicans at Aransas has also greatly decreased in the last couple of weeks. The migration of whooping cranes and white pelicans at approximately the same time across North America leads several people to report large flocks (20+ birds) of whooping cranes. What they really are seeing, however, are white pelicans. The two species look amazingly alike at a distance, both large white birds with black wing tips and an identical spiral flight pattern in migration. However, whooping cranes usually migrate in small groups of up to 8 birds, and frequently migrate as singles, pairs, or family groups.

Tom Stehn
Whooping Crane Coordinator


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