Instead of waiting for an old, re-commissioned satellite to pick up three hits from a bird’s transmitter and triangulate the location, the new CTT units provide a GPS track history of exactly where the bird has been since the last update. In the past we would get a couple of locations during their return migration and we would simply connect the dots with straight lines to estimate the course.
As you can see in the last report, Heather was able to show the exact route they took. This is one of the first times we have been able to graphically show how closely they follow the path we showed them last year.
It makes you wonder just what it was they were learning on the way south. It’s hard to believe they gathered any information at all from so many weather delays, hour-long rodeos around the departure points and the times when some of them had to be crated to the next stopover.
Even flying at 4000 feet you can only see 20 miles or so in all directions and that is on the clear days. And it’s not like our route is lined with obvious landmarks. Most of Illinois looks pretty much the same from the air as does Kentucky or Alabama.
In a preliminary study in 1996, we led Sandhill cranes from Port Perry, Ontario to Virginia. We flew around the east end of Lake Ontario and then southwest to Environmental Studies at Airlie near Warrenton, VA. On the way back, the birds flew straight north – making a beeline for home until they hit the south shore of Lake Ontario near Rochester, NY. It took them some time but they eventually made their way around the west end of the lake and back to Port Perry. That means they were 190 miles from anything they had flown over. Even with super crane vision, they couldn’t have seen that far, so we know they don’t recognize the route from visual clues, at least not entirely.
We also know that if they don’t fly at least part of the route, they get lost on the way back. Case in point are the 2014 birds that we trucked from Wisconsin to Tennessee to avoid the early onset of winter. We flew them the last half of the migration route and in the spring, they followed that path north until they ran out of information in southern Illinois — but what information were they lacking??
In our early studies with Sandhills, we even tried stage-by-stage migration where birds were trucked 50 miles, released to fly around, then trucked another 50 miles. We hoped they would connect the dots to find their way home, but it didn’t work. Brooke Pennypacker and Environmental Studies at Airlie carried some Canada geese aloft in large cage suspended below a gas filled balloon, hoping the birds could simply witness the migration in a passive sort of way and find their way back. But after they were dropped off, they didn’t return.
And why is it that some birds instinctively know how and where to migrate while others need to be shown the route. Precocial birds like cranes leave the nest almost immediately after hatching and follow their parents through the marsh to learn what to eat. They are considered more advanced than altricial birds, like passerines that are hatched naked with their eyes closed. They can’t keep themselves warm and the parents deliver their food until they fledge. Once out of the nest, they are on their own.
Some European Cuckoos are parasitic nesters laying their eggs in the nests of other birds, then leaving. Their offspring have no connection to their biological families yet they can migrate on their own to the same habitat used by their parent, thousands of miles away. Wouldn’t it be handy if cranes retained that instinctive migration knowledge while developing those other skills?
I am not much of a believer in the afterlife but I wish, as a reward for all the hard work of living, we would get twenty minutes after we die with a panel of experts who knew the real answers to questions like what is the origin of the universe, where is Jimmy Hoffa and how do cranes migrate?