Bird Migration: Redefining Reality

Written by: Mary Humes, Field Investigation Teacher

Migration … the movement of billions of birds, navigating vast distances across the Earth through varied and challenging climates and terrain and seemingly limitless ocean expanses, negotiating headwinds, weather extremes, human-made structures, and the constant threats of starvation, dehydration, predation, and exhaustion, (mating, reproducing, raising offspring) and then, doing it all over again in reverse … is a triumph of survival that is one of the most miraculous events on planet Earth. And we get to witness it, twice a year, every year! Science has recently begun to unlock some of the survival secrets that birds employ during their long, perilous journeys, and we are learning that the challenges of migration cause some bird species to redefine previously thought physiological limits. Here are a few examples of migratory birds’ gritty, gutsy efforts to endure their epic expeditions:

Fast Fasting: Flying 55 miles per hour for 11 straight days without sleep, food, or water, the Bar-tailed Godwit covers the distance from one end of the Earth to the other, flying almost 8000 miles from Alaska to New Zealand, the longest non-stop flight of any bird. To prepare for this migratory marathon, this bird first packs on a lot of fat and then, incredibly, consumes part of its own liver and digestive tract and shuts down its kidneys. Advantageous weight reduction
is the reason for the curiously unnatural act of consuming its own organs … after all, it’s not going to need them during its long flight.

A Brain Break: The Swainson’s Thrush has half a mind to take on its 3000-mile trip from South America to Alaska … literally. One of several tactics this bird uses to accomplish its mind-blowing marathon is to alternate putting each half of its brain to sleep in nine-second intervals while the other half continues functioning to avoid predators and mid-air collisions.

Packing Its Carry-on Like a Pro: To prepare for its 24-hour non-stop 2000-mile journey across the Gulf of Mexico, the Ruby-throated Hummingbird can double its body weight in a matter of days. With one of the fastest metabolisms of any animal (the human equivalent of 150,000 calories a day), it will burn all that fat and some lean body mass too, arriving at its final destination as little more than a feathered skeleton.

So the next fall or spring when you see one of those V-shaped arrangements of geese streaking across the sky, look up in awe, amazement, and appreciation for the marvelous miracle that is migration.