What’s all this talk about flying in formation?
- John Lorson: The Rail Trail Naturalist
- January 25, 2020
- 1175
Flying in an echelon, or “V,” provides crucial energy savings to migrating waterfowl. Sandhill cranes can easily be distinguished, even as silhouettes, from similar-sized herons and egrets, as cranes fly with necks extended and long legs trailing while the others draw their necks in during flight.
When a Shreve area reader recently wrote with a question, my comedic instincts from 23 years of humor writing reflexively kicked in. Dean asked, “Why do birds ‘talk’ when they are flying. Geese certainly do, and we have had sandhill cranes over here in Shreve who 'chirrup' when they fly. Not world changing, but I can't figure it out — whether it is cloudy, rainy, clear as a bell, they ‘talk.’”
My mind immediately went to an old punchline on the very same subject: “When geese fly in a ‘V,’ they are typically being led by an older, dominant male bird. The chatter that you hear behind is typically from females of the same generation insisting that he’s going too fast, too slow or headed in the wrong direction altogether.”
Fortunately science has better answers than the average smart aleck. The echelon, “V” or “J,” that waterfowl assemble themselves into when flying is a factor in the vocalization between members of the flock. (The echelon can sometimes present itself as a single “stair-stepped” line as well. This is often the case with the smaller flocks of sandhill cranes we see in our area.)
The echelon formation is all about efficiency. The lead bird in the configuration is doing considerably more work than those in its wind shadow. The birds taking up positions slightly behind and to the left and right are settled into a “sweet spot” where swirls of air called upwash vortices make the whole effort of flight considerably less energy consumptive. In layman’s terms it’s about 20-30 percent easier to fly in the leg of an echelon than to fly at the front. A study in the 1970s found that such “team effort” enables the flock to travel 71 percent further on the same amount of energy as birds traveling alone.
Are birds taught these calculations in flight school? No, but while instinct does start them in the right direction, experience is the greatest teacher, and the birds can easily feel the difference between the right and wrong positions. I can speak to this on a personal level as a bicycle racer, as we ride in the same formations for the very same reasons.
So where does this lead us with regard to the original question of birds “talking” while they’re flying? Scientist believe the vocalizations within the flock may serve multiple purposes.
Obviously if one bird is doing 30 percent more work than its flock mates, sooner or later it will need to share the load. Calling may signal the need for another bird to do the heavy lifting for a while. As the leader fatigues, the followers may hear it in his or her voice and step up. The efficiency of the flock as a whole is dependent upon staying aloft and moving forward. Just like aircraft, it takes a lot more energy to take off and gain height than to simply cruise along at a given altitude and speed. Switching leaders mid-air keeps the flock aloft and prevents individuals from becoming so energy depleted they need to stop entirely to refuel.
Some suggest the birds in the rear are calling encouragement to the leaders, but more likely they are simply affirming they are there. Remember, the lead bird is facing forward for aerodynamic advantage and not looking over a shoulder to see what’s up with the gang. It wants to know that when it’s time for a break, someone’s going to be taking over the lead shift.
Studies have suggested in-air vocalizations during night flight and heavy weather conditions like fog may carry directional messages. Remember, too, that birds in flight also are sometimes looking for feeding and resting opportunities. Calling out and responding to calls from below can guide birds to a safe landing — or in the case that the ground call is coming from a well-practiced hunter, it might be an invitation to a meal where the birds are the main course.
The sandhill cranes mentioned in Dean’s letter deserve more discussion than I’ve left myself space to address, so I’ll be writing about them next time around. Be sure to join me.
Remember, if you have comments on this column or questions about the natural world, write The Rail Trail Naturalist, P.O. Box 170, Fredericksburg, OH 44627, or email jlorson@alonovus.com.