Forecast and Analysis

Regional Migration Analysis: 30 August – 6 September 2013

Andrew Farnsworth The Cornell Lab Sep 06, 2013

Continental Summary:

Movements across the West continued at light to moderate intensities characteristic of the last weeks, perhaps now past peak levels in portions of the Interior West, while the East experienced several pulses of moderate to heavy movements with the passage of two frontal boundaries, harbingers of things to come. Birds on the move this week included Warbling Vireo, Swainson’s Thrush, numerous warblers, Lincoln’s Sparrow, and Baltimore Oriole.



Although scattered precipitation across the region kept migrants on the ground where it fell, light to moderate movements were still in evidence this week in many areas. In particular, migration was in evidence from the Central Valley of California South and East through the Desert Southwest nearly every night in the forecast period. Additionally, movements were apparent from the Yellowstone area South and East along the eastern front of the Rockies into New Mexico. Here is an account from Ted Floyd of some nocturnal listening during early morning of 30 August. As precipitation moved into the Pacific Northwest to end the period, light to moderate movements continued from the Great Basin to the Central Valley and in the Desert Southwest. Birds on the move this week included Warbling Vireo, Swainson’s Thrush, Townsend’s and Orange-crowned Warblers, and Western Tanager.

Great Plains

The weekend began with two disturbances moving across the region, bringing favorable conditions as they passed and facilitating moderate to heavy movements from the Canadian border to the southern Plains. As high pressure built in to begin the week, movements diminished substantially with the exception of eastern Kansas and Oklahoma. With high pressure setup to the East and North, a similar pattern of greatly diminished movements continued through midweek and continuing to the end of the period. Birds on the move this week included American Golden-Plover, Caspian Tern, Blue-headed and Warbling Vireos, Nashville Warbler, and Lincoln’s Sparrow.

Upper Midwest and Northeast

Scattered light to moderate movements over the southern Ohio River drainage began the forecast period, as high pressure sat over western Pennsylvania. However, unstable air spread over much of the Northeast, shutting down movements for the weekend for most areas other than the localized moderate to heavy movements of the western Great Lakes region. As these disturbances moved East, and a cold front crossed the region, conditions improved on Monday night for more widespread moderate to locally heavy movements to spread farther South and East. Between this departing front and another approaching cold front above the Great Lakes, midweek saw high pressure clearing the skies but keeping migration primarily light and scattered. Note, however, that coastal movements on Tuesday night were more intense, with some areas of moderate and even locally heavy migration from Maine to DelMarVa. This second cold front pushed into the region late Wednesday night, spawning a new suite of moderate to heavy movements from the Upper Mississippi River to the Adirondacks. As the high behind the front moved East, Thursday night saw moderate to heavy movements in many areas of the Northeast from Pennsylvania North and East through New England. One account from upstate New York highlights the nocturnal flight calls occurring early in the morning of 6 September. Birds on the move this week included Common Nighthawk, Warbling Vireo, Veery, Swainson’s and Wood Thrushes, Tennessee, Nashville, Blackpoll, Bay-breasted, Magnolia, Palm, Black-throated Green, and Chestnut-sided Warblers.

Gulf Coast and Southeast

The Southeast experienced a period of several days with widespread light movements as a frontal boundary sat over north Texas and a high pressure center sat over the Gulf of Mexico. This frontal boundary slowly moved East and South, eventually stalling over the region on Tuesday night, but spawning moderate to locally heavy movements across its length from north Texas to the Carolinas. This pattern continued on Wednesday night, though muted from the previous night’s intensities, and into Thursday night, with a few areas of more intense migration in the Carolinas and Florida Panhandle. Birds on the move this week included Blue-winged Teal, Common Nighthawk, Least Flycatcher, Yellow, Mourning, and Wilson’s Warblers, and Baltimore Oriole.