Looking Back: Fifteen Years of Aircraft-led Migration
Article #3 in a Series
by Jane Duden

Nature Rules Migration
The duration of aircraft-led migrations over 15 years were always much longer than those of wild cranes. Why?

Joe Duff, Operation Migration

In fifteen years of ultralight-guided migrations, the number of days to complete each one varied greatly but was always much longer than those of wild cranes.

Cranes + Planes = Longer Travel Time
Wild cranes flying have completed migration as quickly as 4-6 days. In contrast, the first five ultralight-led migrations took an average of 55 days from start to finish. The second five fall journeys averaged 85 days, the equivalent of an extra month. The trend continued and the 15th and final year took 115 days, with the birds finally delivered in crates. Just two migrations celebrated November finishes. Four achieved December finishes. But nine times the migration stretched into the next calendar year. You must be asking: Why did aircraft-led journeys south take so long?

Why a Slower Journey?
Reason number one was weather. Some years the planes and cranes were grounded by un-flyable weather for up to 10 or more days in a row.

Unlike birds in nature, the tiny ultralight planes needed perfect conditions to keep the birds and pilots safe. Each morning around sunrise the pilots decided whether or not to fly. In the early years before cell phone apps, the pilots looked at the windsock, listened to a weather station or took a test flight in the tiny aircraft. Headwinds, tailwinds, gusty winds, fog, ice or frost, rain and lightning, temperatures too hot, too cold, or just right—each weather factor affected their decision. Like Goldilocks, the Operation Migration pilots knew what was best when cranes must fly with ultralight planes. They didn't want these valuable birds overheated, overtired, or colliding with other birds or the plane's wing. If conditions were poor in the morning, there was no flight that day.

Cranes behind ultralights also couldn't fly as long or far as cranes in the wild. Operation Migration pilots had a big surprise when they landed the Class of 2002 in Florida at the end of a 49-day journey south: Four birds from the Class of 2001 beat them to Florida— after making their first unassisted south migration in just six days!

Advantages for Wild Cranes
Normally, cranes in the wild migrate during midday when the sun's heat is the strongest and creates thermals (rising columns or updrafts of warm air). The cranes soar and coast on these "elevators," seldom flapping their wings. Under good conditions, wild cranes can stay aloft for hours, covering hundreds of miles with little effort.

Behind the ultralights, birds had to flap their wings to stay aloft—expending more energy and limiting their flights to relatively short distances each day. Their flights may have lasted an hour or two and covered as few as 40 miles at a time—tiny journeys compared to those of wild birds. Instead of using thermals like wild birds, these captive-bred birds learned to use the wing of the aircraft and the wake of air the wing creates to "surf" through the sky and ease their workload. This could only happen when the air was smooth and the wing remained stable. If the plane met turbulence and the wing began to bounce around, the birds had to move away and follow from a safe distance. They were then forced to flap-fly, and soon got tired. So, ultralight flights were limited to early morning when the air is usually calmer. This also helped prevent the young cranes from soaring away on thermals, and possibly getting lost.

Following is Important
When weather delays added up, why didn't the team just put the birds in crates and truck them to the next stop? Cranes are among the species that learn their migration route by following their parents. As substitute parents, the ultralight pilots took that responsibility. Operation Migration pilot Joe Duff explained, "We do know that while taking them south in crates does not work, leading them there does. Maybe it’s as simple as this: Cranes know where they are because they got there themselves and that chain of knowledge is broken when they are put in crates and transported somewhere unfamiliar. We are not prepared to risk their ability to migrate, simply because we have been stuck for days with un-flyable weather. This project is not about the people on the team—it's about the birds."

Indeed, the fifteen years proved that nature is in charge of migrations. Starting in 2016, the journey south for the eastern flock was left up to birds leading birds. Safe journeys!

By Jane Duden
November, 2016