Remember, “fall” migration is not just associated with the official fall season as defined by the autumnal equinox – movements can began as early as mid-June for individuals of some species. You can follow fall migration on  You can sign up for eMail alerts when migration is predicted to be high in the Philadelphia area. BirdCast has often used 1 August as a proxy for the fall migration season’s beginning, because by this point in the year, numbers of birds are beginning to increase markedly in our radar data such that avian movements are now readily apparent above summer’s typically heavy insect and bat activity in many areas.

Most keen observers are excitedly tracking movements of adult and young birds as they begin, engage in, and end their journeys from breeding and natal areas to non-breeding and wintering areas. Days are growing shorter and weather is slowly shifting (very slowly in some cases) away from summer patterns as the sun’s seasonal position in the Northern Hemisphere sky drifts toward the winter solstice.

How will patterns compare to previous years? Visit the Migration Dashboard to see how migration in your local county and state compare to previous years’ averages; or explore counties and states around the contiguous US! Will we see another 850 million bird movement in early October (to view that night’s epic flight, check out 3 October 2021 in our live migration maps)?

Information from Cornell Lab of Ornithology