Each year the National Audubon Society and the Cornell Lab of Ornithology spearhead the Great Backyard Bird Count. Birdwatchers from across the United States and Canada count birds at least once, for at least 15 minutes. The birds observed are then reported on the GBBC web site.
Last year, over 60,000 birdwatchers submitted over 63,000 lists, reporting 623 species and six million birds in the process. The reports helps scientists and conservationists study population trends, track the spread of disease, etc.
You are enocuraged to participate, even if you just watch the birds in your backyard.