A birding survey is one way to get to know what birds are in your area of choice for that particular time of the year.  You could have surveys of migrating, breeding or even wintering birds. If done over a period of time could give clues at to changes in population, density and health of the environment.  Pictured above is a breeding Prothonotary Warbler taken 6/00 in Burlington County by Chip Krilowicz