Fall migration is for the birds… but why?

By Dale Wade
I heard them before I saw them, of course. Their distinctive honk-honk-honk alerts me that fall is here and winter is not far behind. Some snow geese (Anser caerulescens) are on their way to winter in the Southern U.S. Others fly as far as Central Mexico. Birds are in the midst of the great bird fall migration. When I say birds, I mean some 4.7 billion of them.

Why do birds migrate?

Simply put, there are two main reasons why birds migrate: food and cold. As winter approaches, the supply of seeds, nuts, grains, and insects decreases. That, as well as shorter days and cooler temperatures, alert the birds to move on to better climes. Genetic predisposition pushes many with a strong urge to head south.

When can you see birds migrating?

Birds are either diurnal or nocturnal migrants. Those that you typically see during the day, diurnal migrants, will fly during daylight. That includes many strong fliers like raptors, pelicans, and even hummingbirds.

Birds that travel at night, nocturnal migrants, are generally those that you rarely see during the day. That includes those that prefer thick vegetation or wooded areas, rarely leaving those habitats. Flying at night gives birds like thrushes, warblers, and orioles protection from predators. They feed and rest during the day to prepare for another long night of travel.

How far do birds migrate?

Well, that depends on the birds. Migrants range from short- to medium- to long-distance travelers. Short-distance migrants may move from a higher elevation to a lower one. Medium-distance migrants may leave the Northern states and head to Florida or Texas, not unlike us RVers. 

It is the long-distance migrants that astonish us. The whooping crane will easily leave Wood Buffalo National Park in Alberta and arrive 50 days later at Aransas National Wildlife Refuge in Texas. That is a bit over 2,500 miles through the Central Flyway. (Explore the four flyways.)

Not to be outdone, the Rufous hummingbirds depart from Alaska and head to Central America via the Pacific Flyway, traveling some 4,000 miles in just a few weeks. 

Ruby-throated hummingbirds leave their Northern U.S. habitats for Mexico, traveling more than 2,000 miles. That includes a 22-hour non-stop flight over 600 miles of the Gulf of Mexico.

How can you find out which birds are migrating in your area?

The Cornell Lab of Ornithology, Colorado State University, and University of Massachusetts-Amherst have banded together to create Birdcast. This application released in 2018 uses Doppler weather radar data to track when, where, and how far birds migrate in real-time. The dashboard lets you enter your county and state to see the latest information about bird migration in your region. It even lets you enter your city for a closer look at what to expect. I believe that you will be totally amazed at what you find. (Need to identify that bird? Review these simple steps.)

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