Peak Broad-winged Hawk migration is generally between the 15th and 25th of the month, although good numbers have been observed as early as the 12th. Major flights of migrating Broad-wings may be seen anywhere in the county. Large numbers have been counted at Schooley Mill Park, Centennial Park, and the Skywatch at Mt. Pleasant.
Although Merlins may be sighted as early as late August, numbers increase by the middle of this month.
Shorebirds can still be found on mudflats, along pond edges, and in short-grass areas throughout the month.
From late August to mid-September, check extensive short-grass areas such as turf farms for Buff-breasted Sandpipers. American Golden-Plovers may drop in this month, while Black-bellied Plovers may continue through October. All share their favored habitat with ever-present Killdeer. On weekdays, the sports fields at Western Regional Park are worth scanning.
Migrant terns over lakes and reservoirs continue to be a good possibility throughout this month.
Barred and Great Horned owls are again calling frequently.
Whip-poor-wills typically leave this month, although it has become increasingly hard to tell because there are few, if any, that still breed locally.
Ruby-throated Hummingbirds will be going through in dwindling numbers by the end of the month; only a few linger into early October.
Red-headed Woodpecker migration seems to peak the last two weeks of this month and the first week of October. Keep an eye out for brown-headed juveniles as well as adults.
Yellow-bellied Sapsuckers begin to show up the third week of the month.
Most flycatchers, other than Eastern Phoebes which remain into October or later, are gone by mid to late September; a few calling pewees have been detected until mid-October.
Red-breasted Nuthatches may begin to appear in pine or mixed pine/deciduous woods. The first migrants are often seen at feeders.
Kinglets may begin to arrive in September, although the earliest Ruby-crowns may have put in an appearance in late August. The majority of both species do not move in until October.
Look for the largest number of migrating warblers this month. They are usually seen in small groups, frequently in the vicinity of water, often in association with mixed chickadee, titmouse, and nuthatch flocks. Migrants are often found in black walnut and various species of oak, hickory, ash, and willow trees. Grapevines and poison ivy tangles are also excellent possibilities. After cool nights, look for activity in areas that are warmed by early sun. During the last few hours of daylight, there is another period of feeding before the night flight.
Take a second look at any possible Tennessee Warbler to be sure you don’t have a Philadelphia Vireo.
Autumn is the time to watch for the elusive Mourning and Connecticut warblers. The Mourning’s migration period runs from late August to early October, although September brings the largest numbers. Connecticut Warblers (which are not spring migrants in Maryland) should be looked for from the beginning of the second week in September to mid-October. The last half of September usually is the peak period.
From mid-September to late October, search brushy weed patches, especially those close to water, for Lincoln’s Sparrows.
Both White-throated Sparrows and Dark-eyed Juncos may arrive during the first half of the month, but numbers are few until late September or early October.
Rose-breasted Grosbeak numbers normally peak the last half of the month.
Look for migrating Bobolinks from early September to late October.
While scanning the sunny late summer and autumn skies for migrating birds, note the passage of Monarch butterflies. They may begin moving an hour or two after sunrise and may be seen at altitudes of hundreds of feet as well as close to the ground. Several dozen an hour will frequently be tallied.