Birding Through the Seasons - September
Land-bird migration peaks this month. Every autumn, more than five billion birds mi-grate across North America, crossing the United States at rates of tens of millions a day. Many of these birds fly over Pennsylvania. The majority of Pennsylvania's song-birds are long-distance migrants; that is, they fly to the southern states, the Caribbean, or Central or South America for the winter. For this journey they must fatten them-selves up, making them most commonly seen foraging for seeds, grain or insects in fields and woods this time of year.
Since songbirds migrate at night, it is hard to see this vast movement. Groups of birds in migration are often seen following cold fronts or stormy nights. Observations made with weather radar or telescopes focused on the full moon have shown processions of, and one observer estimated their passage over his area at the rate of 9,000 per hour. This gives some indication of the numbers of birds in the air at night during migratory peaks.
Backyard and woodland birds are noticeably quiet in late summer and are not easily seen. However, do not be deceived, for there are more birds in the woods and fields right now than during any other time of the year. Even though there are more individuals, they are difficult to see, in part, because they are quiet, but also because the colorful males have, or are in the process of, losing their bright breeding plumage, attaining more earth-toned camouflaging colors. Males are not singing as they did in spring migration, so are not as conspicuous. One group has, as a result, gained the distinction of being "confusing fall warblers!" This accounts for the fall migration being less dramatic than spring. In addition, the fall movement is distributed over a longer period.
As September passes, the raptor migration picks up and produces the peak number of American Kestrel, Osprey, adult Bald Eagles, and notably the Broad-winged Hawks. Also by the end of September, many of the shorebirds and most of the hummingbirds, vireos, and warblers have left for warmer climates and are replaced by the beginning of the sparrow movement.
Hawk Mountain Sanctuary draws thousands annually to observe this mass-movement of large birds, one of Pennsylvania's avian spectacles. But many other ridge-top vantage points also attract observers and produce similar counts. Other key hawkwatching sites that have official daily counts in the fall include Allegheny Front, Bedford County; Militia Hill , Flourtown; Rose Tree Park, Media; Tuscarora Summit, Franklin County, Waggoner's Gap, Perry and Cumberland counties; Second Mountain, Fort Indiantown Gap; and Bake Oven Knob, Lehigh and Carbon counties.
Pennsylvania Game Commission