Bird migration still defies easy landing

Bird migration is one of nature’s most fascinating – and still mysterious – events. On the surface, it may seem straightforward, but if you take a closer look, you’ll see layers of remarkable complexity.

There are more than 11,000 species of birds, and about 40 percent migrate in some form. These migrations range from simple elevational shifts for mountain species, to short-distance movements to avoid bad weather, to long journeys to warmer climates to escape winter – and, in some cases, the ultimate trek: traveling from one end of the Earth to the other. Clearly, migration is more complex than it may first appear.

In the 1800s, people knew little about migration. Many thought it was impossible for a tiny bird to navigate great distances and endure such physical demands, so “facts” were invented – including claims that hummingbirds migrated on the backs of geese to escape winter.

Others believed birds dove to the bottoms of ponds and spent the winter buried in mud. Today, such theories seem preposterous, yet at the time they were widely accepted as fact – attempts to explain the unexplainable.

In the 1900s, scientists began developing new ways to study birds. Early attempts at tracking migration included catching a bird and tying a brightly colored ribbon to its wing, hoping to relocate the same bird during winter. The method was inefficient – and only possible if researchers already had an idea where the bird spent the season.

The invention of transistors in the 1940s was a breakthrough that made small electronics possible. By the end of the 1900s, researchers were using lightweight tracking devices to follow the movements of free-flying birds. It marked the beginning of a deeper understanding of bird migration, though still just the tip of the iceberg.

In the past few decades, new and sometimes almost unbelievable discoveries have turned our understanding of bird migration upside down. Today, there are many ways to track migrating birds.

One tool is BirdCast, a website from the Cornell Lab of Ornithology. By entering your county and state, you can see how many birds passed over your area the previous night during migration season.

There’s a ton of information available to anyone curious about migration. In addition to daily tallies of birds passing through your county, BirdCast provides details on the timing of each nightly flight, along with flight direction and altitude. They also include a list of the species expected to be on the move.

For example, as I write this, 97,400 birds passed over my county last night. At one point, 36,400 were in flight, traveling south-southwest at 14 mph and at an altitude of 600 feet – all at once.

To gather this data, BirdCast uses information from the national network of weather surveillance radars (NEXRAD). Sophisticated algorithms and machine-learning models separate precipitation and other weather patterns from biological signals such as birds.

The system then analyzes the strength of those signals to estimate the number of birds in flight. Like a weather forecast, it can even predict nocturnal bird migration for the nights ahead.

We’ve sure come a long way in understanding bird migration, unlocking some of nature’s most mysterious events. However, there is still much we don’t understand about bird migration – and much more we’ll learn in the years ahead. 

Until next time …

Editor’s note: Stan Tekiela’s NatureSmart column appears twice a month in the Eden Prairie Local News. Tekiela is an author, naturalist and wildlife photographer who travels extensively across the United States to study and capture wildlife images. 

You can follow his work on Instagram and Facebook. He can be contacted via his website at www.naturesmart.com.