Every fall, millions of birds fly south to spend the winter in sunny places with mild climates and plentiful food. Most smaller birds migrate under the cover of darkness, stopping to fuel up on insects or seeds by day and using the stars to guide them at night. Hawks, by contrast, are diurnal migrants; they depend on currents of rising warm air to lift them to high altitudes where they glide on their broad wings without flapping, thereby conserving energy. During these flights, hawks use their keen eyesight to recognize landmarks, follow landforms that provide rising thermals, and steer a course to their ancestral wintering grounds. In some places these migrating hawks gather in huge numbers, and people gather to watch them with binoculars and data sheets in the phenomenon known as the hawkwatch.
Counting hawks during migration is more than a competitive pursuit for list-oriented birders. The data collected at hawkwatches helps experts monitor the health of various ecosystems. Because hawks are top predators -- that is, they occupy the top of the food chain -- they're very sensitive to changes that affect prey species. Comparing hawk numbers from year to year reveals trends that offer insight into the well-being of the environment in both the breeding and wintering areas.
But more than simply counting hawks, there's the spectacle of it all. Standing atop a ridge on a crisp autumn day while hundreds of hawks circle and stream past is an unforgettable experience, which helps explain why people return to these sites day after day and hawkwatch programs across the country attract volunteers by the dozens. Visit any hawkwatch site, and you'll find people who came one day out of curiosity and soon became regulars.
Click here for a guide to some of the top hawkwatch sites in North America.